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<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom">
<title>小破站</title>
<subtitle>の日常操作</subtitle>
<link href="/atom.xml" rel="self"/>
<link href="https://keee.top/"/>
<updated>2020-05-22T10:05:53.000Z</updated>
<id>https://keee.top/</id>
<author>
<name>Glimmer</name>
</author>
<generator uri="https://hexo.io/">Hexo</generator>
<entry>
<title>60行代码不到用Python下载无水印抖音视频</title>
<link href="https://keee.top/2020/052213760.html"/>
<id>https://keee.top/2020/052213760.html</id>
<published>2020-05-22T10:05:53.000Z</published>
<updated>2020-05-22T10:05:53.000Z</updated>
<content type="html"><![CDATA[<blockquote><p>用到的库 <code>BeautifulSoup</code> ，解析用的是 <code>html.parser</code></p></blockquote><h5 id="模拟-Android-手机浏览器-UA"><a href="#模拟-Android-手机浏览器-UA" class="headerlink" title="模拟 Android 手机浏览器 UA"></a>模拟 <code>Android</code> 手机浏览器 <code>UA</code></h5><figure class="highlight python"><table><tbody><tr><td class="code"><pre><span class="line">ua_phone = {<span class="string">'User-Agent'</span>: <span class="string">'Mozilla/5.0 (Linux; Android 6.0; '</span></span><br><span class="line"> <span class="string">'Nexus 5 Build/MRA58N) AppleWebKit/537.36 ('</span></span><br><span class="line"> <span class="string">'KHTML, like Gecko) Chrome/80.0.3987.116 Mobile Safari/537.36'</span>}</span><br></pre></td></tr></tbody></table></figure><h5 id="模拟-Windows-浏览器-UA"><a href="#模拟-Windows-浏览器-UA" class="headerlink" title="模拟 Windows 浏览器 UA"></a>模拟 <code>Windows</code> 浏览器 <code>UA</code></h5><figure class="highlight python"><table><tbody><tr><td class="code"><pre><span class="line">ua_win = {<span class="string">'User-Agent'</span>: <span class="string">'Mozilla/5.0 (Windows NT 10.0; Win64; x64) '</span></span><br><span class="line"> <span class="string">'AppleWebKit/537.36 (KHTML, like Gecko) '</span></span><br><span class="line"> <span class="string">'Chrome/80.0.3987.116 Safari/537.36'</span>}</span><br></pre></td></tr></tbody></table></figure><h5 id="对分享的链接进行截取，获得标题跟视频播放的链接"><a href="#对分享的链接进行截取，获得标题跟视频播放的链接" class="headerlink" title="对分享的链接进行截取，获得标题跟视频播放的链接"></a>对分享的链接进行截取，获得标题跟视频播放的链接</h5><figure class="highlight python"><table><tbody><tr><td class="code"><pre><span class="line"><span class="comment"># 待解析的视频url</span></span><br><span class="line">parse_url = input(<span class="string">">>请输入抖音分享的完整链接："</span>)</span><br><span class="line">str_http = <span class="string">"http"</span></span><br><span class="line"><span class="keyword">while</span> parse_url.find(str_http) == <span class="number">-1</span>:</span><br><span class="line"> parse_url = input(<span class="string">"请输入正确的链接："</span>)</span><br><span class="line">title_index = parse_url.index(str_http)</span><br><span class="line">copy_index = len(parse_url)</span><br><span class="line">str_copy = <span class="string">"复制此链接"</span></span><br><span class="line"><span class="keyword">if</span> parse_url.find(str_copy) != <span class="number">-1</span>:</span><br><span class="line"> copy_index = parse_url.index(str_copy) - <span class="number">1</span></span><br><span class="line">title = parse_url[<span class="number">0</span>:title_index]</span><br><span class="line"><span class="keyword">while</span> len(title) == <span class="number">0</span>:</span><br><span class="line"> title = input(<span class="string">">>请输入视频标题："</span>)</span><br><span class="line">url = parse_url[title_index:copy_index]</span><br><span class="line">print(<span class="string">f'>>原链接：<span class="subst">{url}</span>'</span>)</span><br></pre></td></tr></tbody></table></figure><a id="more"></a><h5 id="请求原链接进行解析得到有水印的链接跟无水印链接"><a href="#请求原链接进行解析得到有水印的链接跟无水印链接" class="headerlink" title="请求原链接进行解析得到有水印的链接跟无水印链接"></a>请求原链接进行解析得到有水印的链接跟无水印链接</h5><figure class="highlight python"><table><tbody><tr><td class="code"><pre><span class="line"><span class="comment"># 解析url</span></span><br><span class="line">url_source = requests.get(<span class="string">f'<span class="subst">{url}</span>'</span>, headers=ua_win)</span><br><span class="line">soup = BeautifulSoup(url_source.text, <span class="string">'html.parser'</span>)</span><br><span class="line">play_arr = soup.prettify().split(<span class="string">'playAddr: "'</span>, <span class="number">1</span>)</span><br><span class="line">url_origin = <span class="string">""</span></span><br><span class="line"><span class="keyword">if</span> len(play_arr) > <span class="number">1</span>:</span><br><span class="line"> str_temp = play_arr[<span class="number">1</span>]</span><br><span class="line"> index = str_temp.index(<span class="string">"\","</span>)</span><br><span class="line"> url_temp = str_temp[<span class="number">0</span>:index]</span><br><span class="line"> print(<span class="string">f'>>有水印链接：<span class="subst">{url_temp}</span>'</span>)</span><br><span class="line"> url_origin = url_temp.replace(<span class="string">"playwm"</span>, <span class="string">"play"</span>)</span><br><span class="line"> print(<span class="string">f'>>无水印链接：<span class="subst">{url_origin}</span>'</span>)</span><br><span class="line"><span class="keyword">else</span>:</span><br><span class="line"> print(<span class="string">">>解析无水印链接失败"</span>)</span><br></pre></td></tr></tbody></table></figure><h5 id="进行视频下载保存到本地"><a href="#进行视频下载保存到本地" class="headerlink" title="进行视频下载保存到本地"></a>进行视频下载保存到本地</h5><figure class="highlight python"><table><tbody><tr><td class="code"><pre><span class="line"><span class="comment"># 下载视频</span></span><br><span class="line"><span class="keyword">if</span> len(url_origin) > <span class="number">0</span>:</span><br><span class="line"> print(<span class="string">">>开始下载..."</span>)</span><br><span class="line"> <span class="comment"># 拿到无水印链接</span></span><br><span class="line"> url_video = requests.get(</span><br><span class="line"> url_origin,</span><br><span class="line"> headers=ua_phone)</span><br><span class="line"> <span class="comment"># 无水印链接进行视频下载</span></span><br><span class="line"> save_path = <span class="string">f'<span class="subst">{local_path}</span><span class="subst">{title}</span>.mp4'</span></span><br><span class="line"> <span class="keyword">with</span> open(save_path, <span class="string">'wb'</span>) <span class="keyword">as</span> file:</span><br><span class="line"> file.write(url_video.content)</span><br><span class="line"> file.flush()</span><br><span class="line"> file.close() <span class="comment"># 关闭文件</span></span><br><span class="line"> print(<span class="string">f'>>下载完成：<span class="subst">{save_path}</span>'</span>)</span><br></pre></td></tr></tbody></table></figure><h5 id="效果展示"><a href="#效果展示" class="headerlink" title="效果展示"></a>效果展示</h5><p><img src="https://s1.ax1x.com/2020/05/20/YTZftf.jpg" alt="YTZftf.jpg"></p><p><img src="https://s1.ax1x.com/2020/05/20/YTmqYV.jpg" alt="YTmqYV.jpg"></p><h5 id="完整源码："><a href="#完整源码：" class="headerlink" title="完整源码："></a>完整源码：</h5><figure class="highlight python"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">import</span> requests</span><br><span class="line"><span class="keyword">from</span> bs4 <span class="keyword">import</span> BeautifulSoup</span><br><span class="line"></span><br><span class="line"><span class="comment"># 保存的本地路径</span></span><br><span class="line">local_path = <span class="string">"/Volumes/娱乐E/抖音/"</span></span><br><span class="line">ua_phone = {<span class="string">'User-Agent'</span>: <span class="string">'Mozilla/5.0 (Linux; Android 6.0; '</span></span><br><span class="line"> <span class="string">'Nexus 5 Build/MRA58N) AppleWebKit/537.36 ('</span></span><br><span class="line"> <span class="string">'KHTML, like Gecko) Chrome/80.0.3987.116 Mobile Safari/537.36'</span>}</span><br><span class="line">ua_win = {<span class="string">'User-Agent'</span>: <span class="string">'Mozilla/5.0 (Windows NT 10.0; Win64; x64) '</span></span><br><span class="line"> <span class="string">'AppleWebKit/537.36 (KHTML, like Gecko) '</span></span><br><span class="line"> <span class="string">'Chrome/80.0.3987.116 Safari/537.36'</span>}</span><br><span class="line"><span class="comment"># 待解析的视频url</span></span><br><span class="line">parse_url = input(<span class="string">">>请输入抖音分享的完整链接："</span>)</span><br><span class="line">str_http = <span class="string">"http"</span></span><br><span class="line"><span class="keyword">while</span> parse_url.find(str_http) == <span class="number">-1</span>:</span><br><span class="line"> parse_url = input(<span class="string">"请输入正确的链接："</span>)</span><br><span class="line">title_index = parse_url.index(str_http)</span><br><span class="line">copy_index = len(parse_url)</span><br><span class="line">str_copy = <span class="string">"复制此链接"</span></span><br><span class="line"><span class="keyword">if</span> parse_url.find(str_copy) != <span class="number">-1</span>:</span><br><span class="line"> copy_index = parse_url.index(str_copy) - <span class="number">1</span></span><br><span class="line">title = parse_url[<span class="number">0</span>:title_index]</span><br><span class="line"><span class="keyword">while</span> len(title) == <span class="number">0</span>:</span><br><span class="line"> title = input(<span class="string">">>请输入视频标题："</span>)</span><br><span class="line">url = parse_url[title_index:copy_index]</span><br><span class="line">print(<span class="string">f'>>原链接：<span class="subst">{url}</span>'</span>)</span><br><span class="line"><span class="comment"># 解析url</span></span><br><span class="line">url_source = requests.get(<span class="string">f'<span class="subst">{url}</span>'</span>, headers=ua_win)</span><br><span class="line">soup = BeautifulSoup(url_source.text, <span class="string">'html.parser'</span>)</span><br><span class="line">play_arr = soup.prettify().split(<span class="string">'playAddr: "'</span>, <span class="number">1</span>)</span><br><span class="line">url_origin = <span class="string">""</span></span><br><span class="line"><span class="keyword">if</span> len(play_arr) > <span class="number">1</span>:</span><br><span class="line"> str_temp = play_arr[<span class="number">1</span>]</span><br><span class="line"> index = str_temp.index(<span class="string">"\","</span>)</span><br><span class="line"> url_temp = str_temp[<span class="number">0</span>:index]</span><br><span class="line"> print(<span class="string">f'>>有水印链接：<span class="subst">{url_temp}</span>'</span>)</span><br><span class="line"> url_origin = url_temp.replace(<span class="string">"playwm"</span>, <span class="string">"play"</span>)</span><br><span class="line"> print(<span class="string">f'>>无水印链接：<span class="subst">{url_origin}</span>'</span>)</span><br><span class="line"><span class="keyword">else</span>:</span><br><span class="line"> print(<span class="string">">>解析无水印链接失败"</span>)</span><br><span class="line"><span class="comment"># 下载视频</span></span><br><span class="line"><span class="keyword">if</span> len(url_origin) > <span class="number">0</span>:</span><br><span class="line"> print(<span class="string">">>开始下载..."</span>)</span><br><span class="line"> <span class="comment"># 拿到无水印链接</span></span><br><span class="line"> url_video = requests.get(</span><br><span class="line"> url_origin,</span><br><span class="line"> headers=ua_phone)</span><br><span class="line"> <span class="comment"># 无水印链接进行视频下载</span></span><br><span class="line"> save_path = <span class="string">f'<span class="subst">{local_path}</span><span class="subst">{title}</span>.mp4'</span></span><br><span class="line"> <span class="keyword">with</span> open(save_path, <span class="string">'wb'</span>) <span class="keyword">as</span> file:</span><br><span class="line"> file.write(url_video.content)</span><br><span class="line"> file.flush()</span><br><span class="line"> file.close() <span class="comment"># 关闭文件</span></span><br><span class="line"> print(<span class="string">f'>>下载完成：<span class="subst">{save_path}</span>'</span>)</span><br></pre></td></tr></tbody></table></figure><script> document.querySelectorAll('.github-emoji') .forEach(el => { if (!el.dataset.src) { return; } const img = document.createElement('img'); img.style = 'display:none !important;'; img.src = el.dataset.src; img.addEventListener('error', () => { img.remove(); el.style.color = 'inherit'; el.style.backgroundImage = 'none'; el.style.background = 'none'; }); img.addEventListener('load', () => { img.remove(); }); document.body.appendChild(img); }); </script>]]></content>
<summary type="html">
<blockquote>
<p>用到的库 <code>BeautifulSoup</code> ，解析用的是 <code>html.parser</code></p>
</blockquote>
<h5 id="模拟-Android-手机浏览器-UA"><a href="#模拟-Android-手机浏览器-UA" class="headerlink" title="模拟 Android 手机浏览器 UA"></a>模拟 <code>Android</code> 手机浏览器 <code>UA</code></h5><figure class="highlight python"><table><tbody><tr><td class="code"><pre><span class="line">ua_phone = {<span class="string">'User-Agent'</span>: <span class="string">'Mozilla/5.0 (Linux; Android 6.0; '</span></span><br><span class="line"> <span class="string">'Nexus 5 Build/MRA58N) AppleWebKit/537.36 ('</span></span><br><span class="line"> <span class="string">'KHTML, like Gecko) Chrome/80.0.3987.116 Mobile Safari/537.36'</span>}</span><br></pre></td></tr></tbody></table></figure>
<h5 id="模拟-Windows-浏览器-UA"><a href="#模拟-Windows-浏览器-UA" class="headerlink" title="模拟 Windows 浏览器 UA"></a>模拟 <code>Windows</code> 浏览器 <code>UA</code></h5><figure class="highlight python"><table><tbody><tr><td class="code"><pre><span class="line">ua_win = {<span class="string">'User-Agent'</span>: <span class="string">'Mozilla/5.0 (Windows NT 10.0; Win64; x64) '</span></span><br><span class="line"> <span class="string">'AppleWebKit/537.36 (KHTML, like Gecko) '</span></span><br><span class="line"> <span class="string">'Chrome/80.0.3987.116 Safari/537.36'</span>}</span><br></pre></td></tr></tbody></table></figure>
<h5 id="对分享的链接进行截取，获得标题跟视频播放的链接"><a href="#对分享的链接进行截取，获得标题跟视频播放的链接" class="headerlink" title="对分享的链接进行截取，获得标题跟视频播放的链接"></a>对分享的链接进行截取，获得标题跟视频播放的链接</h5><figure class="highlight python"><table><tbody><tr><td class="code"><pre><span class="line"><span class="comment"># 待解析的视频url</span></span><br><span class="line">parse_url = input(<span class="string">"&gt;&gt;请输入抖音分享的完整链接："</span>)</span><br><span class="line">str_http = <span class="string">"http"</span></span><br><span class="line"><span class="keyword">while</span> parse_url.find(str_http) == <span class="number">-1</span>:</span><br><span class="line"> parse_url = input(<span class="string">"请输入正确的链接："</span>)</span><br><span class="line">title_index = parse_url.index(str_http)</span><br><span class="line">copy_index = len(parse_url)</span><br><span class="line">str_copy = <span class="string">"复制此链接"</span></span><br><span class="line"><span class="keyword">if</span> parse_url.find(str_copy) != <span class="number">-1</span>:</span><br><span class="line"> copy_index = parse_url.index(str_copy) - <span class="number">1</span></span><br><span class="line">title = parse_url[<span class="number">0</span>:title_index]</span><br><span class="line"><span class="keyword">while</span> len(title) == <span class="number">0</span>:</span><br><span class="line"> title = input(<span class="string">"&gt;&gt;请输入视频标题："</span>)</span><br><span class="line">url = parse_url[title_index:copy_index]</span><br><span class="line">print(<span class="string">f'&gt;&gt;原链接：<span class="subst">{url}</span>'</span>)</span><br></pre></td></tr></tbody></table></figure>
</summary>
<category term="Python" scheme="https://keee.top/categories/Python/"/>
<category term="抖音" scheme="https://keee.top/tags/%E6%8A%96%E9%9F%B3/"/>
</entry>
<entry>
<title>Android常见UI单位</title>
<link href="https://keee.top/2020/052216966.html"/>
<id>https://keee.top/2020/052216966.html</id>
<published>2020-05-22T10:05:53.000Z</published>
<updated>2020-05-22T10:05:53.000Z</updated>
<content type="html"><![CDATA[<h4 id="UI尺寸单位"><a href="#UI尺寸单位" class="headerlink" title="UI尺寸单位"></a>UI尺寸单位</h4><p>Android 中 <code>TypedValue.applyDimension</code> 单位转换的源码：</p><figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">TypedValue</span> </span>{</span><br><span class="line"> <span class="comment">// ...</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">float</span> <span class="title">applyDimension</span><span class="params">(<span class="keyword">int</span> unit, <span class="keyword">float</span> value, DisplayMetrics metrics)</span> </span>{</span><br><span class="line"> <span class="keyword">switch</span> (unit) {</span><br><span class="line"> <span class="keyword">case</span> COMPLEX_UNIT_PX:</span><br><span class="line"> <span class="keyword">return</span> value;</span><br><span class="line"> <span class="keyword">case</span> COMPLEX_UNIT_DIP:</span><br><span class="line"> <span class="keyword">return</span> value * metrics.density;</span><br><span class="line"> <span class="keyword">case</span> COMPLEX_UNIT_SP:</span><br><span class="line"> <span class="keyword">return</span> value * metrics.scaledDensity;</span><br><span class="line"> <span class="keyword">case</span> COMPLEX_UNIT_PT:</span><br><span class="line"> <span class="keyword">return</span> value * metrics.xdpi * (<span class="number">1.0f</span>/<span class="number">72</span>);</span><br><span class="line"> <span class="keyword">case</span> COMPLEX_UNIT_IN:</span><br><span class="line"> <span class="keyword">return</span> value * metrics.xdpi;</span><br><span class="line"> <span class="keyword">case</span> COMPLEX_UNIT_MM:</span><br><span class="line"> <span class="keyword">return</span> value * metrics.xdpi * (<span class="number">1.0f</span>/<span class="number">25.4f</span>);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">// ...</span></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><a id="more"></a><p>涉及到的单位：</p><ul><li><p>px</p><blockquote><p>像素单位，1px 代表一个像素点，例如我们常说的手机屏幕分辨率是 1080x1920，指的就是该手机宽度有 1080 个像素点，高度有 1920 个像素点。</p></blockquote></li><li><p>dp</p><blockquote><p>也叫 dip，全称 device independent pixels，即<code>设备无关像素</code>，这种尺寸单位在不同设备上的物理大小是相同的，就是说在<strong>屏幕尺寸相同</strong>、但不同的分辨率的手机上，用dp标识的东西，显示的大小是一样的。在每英寸 160 点(一个规定的标准值)的显示屏上，1dp = 1px=1/160 inch，px 跟 dp 的关系是 px = density * dp，density 指的是屏幕密度，它的大小跟屏幕尺寸是无关的。</p></blockquote></li><li><p>sp</p><blockquote><p>全称 Scale-independent Pixels ，与 dp 单位相似，会根据用户的字体大小偏好(手机系统里面有统一字体大小设置)进行缩放，谷歌推荐字体单位就是它。</p></blockquote></li><li><p>pt</p><blockquote><p>1pt＝1/72 inch</p></blockquote></li><li><p>inch</p><blockquote><p>英寸</p></blockquote></li><li><p>mm</p><blockquote><p>毫米</p></blockquote></li></ul><h4 id="其它相关"><a href="#其它相关" class="headerlink" title="其它相关"></a>其它相关</h4><ul><li><p>dpi</p><blockquote><p>全称 Dots Per Inch，指的是每英寸<strong>点数(Dot)</strong>。计算公式： $$\frac{\sqrt{宽^2(单位px)+高^2(单位px)}}{屏幕尺寸(单位inch)}$$，例如小米 Mix 2s，屏幕分辨率为 1920x1080， 屏幕尺寸为 5.99，那么按照公式计算出它的 dpi 为 368(367.76…)，density 为dpi/160=2.29。</p></blockquote><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">val</span> densityDpi = resources.displayMetrics.densityDpi</span><br></pre></td></tr></tbody></table></figure><p><code>ldpi</code>：dpi范围为0 ~ 120</p><p><code>mdpi</code>：dpi范围为121 ~ 160</p><p><code>hdpi</code>：dpi范围为161 ~ 240</p><p><code>xhdpi</code>：dpi范围为241~320</p><p><code>xxhdpi</code>：dpi范围为321~480</p><p><code>xxxhdpi</code>：dpi范围为481及以上</p></li><li><p>xdpi</p><blockquote><p>水平方向上每英寸容纳的点的数量。</p></blockquote></li><li><p>ydpi</p><blockquote><p>垂直方向上每英寸容纳的点的数量。</p></blockquote></li><li><p>ppi</p><blockquote><p>全称 Pixels Per Inch，指的是每英寸<strong>像素数(Pixel)</strong>，数值越大显示越细腻。计算式：ppi = 屏幕对角线像素数 / 屏幕对角线长度。例如上一个例子，小米 Mix 2s，屏幕分辨率为 1920x1080，那么它的对角线像素为 2203，那么它的 ppi=2203/5.99≈368。</p></blockquote><p>DPI 面向的是印刷受体，而PPI面向的是屏幕受体。例如电脑屏幕分辨率为 1920×1080，如果这个电脑屏幕是19.2 英寸，那么电脑屏幕的 PPI=1920/19.2=100PPI；又例如我们现在有张图片分辨率为 1920×1080，如果印刷设备的解析能力刚好是 100DPI，而你要印制的纸张尺寸刚好是 19.2 英寸，那么印刷设备就可以刚好把一个像素作为一个取样点，印刷完成后图片的保真度是百分之百（也就是图片所有的视觉信息都被印刷出来了）。在大多数情况下，这几个数值都不那么整好，因此保真度会产生损失。</p></li><li><p>density</p><blockquote><p>屏幕密度，<strong>它的大小跟手机屏幕大小没有关系</strong>，它与 dpi 的关系是 density=dpi/160。</p></blockquote><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">val</span> density = resources.displayMetrics.density</span><br></pre></td></tr></tbody></table></figure></li></ul><ul><li><p>scaledDensity</p><blockquote><p>默认情况下跟 density 值是一样的，此时 dp 跟 sp 为单位显示的大小是一致的，如果手机系统文字大小设置更改后会发生改变，sp 为单位的时候就会根据这个进行相应的缩放，dp 跟 sp 就不一致了。</p></blockquote><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">val</span> scaledDensity = resources.displayMetrics.scaledDensity</span><br></pre></td></tr></tbody></table></figure></li></ul><script> document.querySelectorAll('.github-emoji') .forEach(el => { if (!el.dataset.src) { return; } const img = document.createElement('img'); img.style = 'display:none !important;'; img.src = el.dataset.src; img.addEventListener('error', () => { img.remove(); el.style.color = 'inherit'; el.style.backgroundImage = 'none'; el.style.background = 'none'; }); img.addEventListener('load', () => { img.remove(); }); document.body.appendChild(img); }); </script>]]></content>
<summary type="html">
<h4 id="UI尺寸单位"><a href="#UI尺寸单位" class="headerlink" title="UI尺寸单位"></a>UI尺寸单位</h4><p>Android 中 <code>TypedValue.applyDimension</code> 单位转换的源码：</p>
<figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">TypedValue</span> </span>{</span><br><span class="line"> <span class="comment">// ...</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">float</span> <span class="title">applyDimension</span><span class="params">(<span class="keyword">int</span> unit, <span class="keyword">float</span> value, DisplayMetrics metrics)</span> </span>{</span><br><span class="line"> <span class="keyword">switch</span> (unit) {</span><br><span class="line"> <span class="keyword">case</span> COMPLEX_UNIT_PX:</span><br><span class="line"> <span class="keyword">return</span> value;</span><br><span class="line"> <span class="keyword">case</span> COMPLEX_UNIT_DIP:</span><br><span class="line"> <span class="keyword">return</span> value * metrics.density;</span><br><span class="line"> <span class="keyword">case</span> COMPLEX_UNIT_SP:</span><br><span class="line"> <span class="keyword">return</span> value * metrics.scaledDensity;</span><br><span class="line"> <span class="keyword">case</span> COMPLEX_UNIT_PT:</span><br><span class="line"> <span class="keyword">return</span> value * metrics.xdpi * (<span class="number">1.0f</span>/<span class="number">72</span>);</span><br><span class="line"> <span class="keyword">case</span> COMPLEX_UNIT_IN:</span><br><span class="line"> <span class="keyword">return</span> value * metrics.xdpi;</span><br><span class="line"> <span class="keyword">case</span> COMPLEX_UNIT_MM:</span><br><span class="line"> <span class="keyword">return</span> value * metrics.xdpi * (<span class="number">1.0f</span>/<span class="number">25.4f</span>);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">// ...</span></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure>
</summary>
<category term="Android" scheme="https://keee.top/categories/Android/"/>
<category term="UI布局" scheme="https://keee.top/tags/UI%E5%B8%83%E5%B1%80/"/>
</entry>
<entry>
<title>Java之线程池</title>
<link href="https://keee.top/2020/05228a7d.html"/>
<id>https://keee.top/2020/05228a7d.html</id>
<published>2020-05-22T10:05:53.000Z</published>
<updated>2020-05-22T10:05:53.000Z</updated>
<content type="html"><![CDATA[<h5 id="线程池体系"><a href="#线程池体系" class="headerlink" title="线程池体系"></a>线程池体系</h5><p><img src="https://s1.ax1x.com/2020/05/21/YbAtat.png" alt="YbAtat.png"></p><ul><li><p><code>Executor</code> 作为线程池最顶层的接口，它里面只有一个 <code>execute</code> 方法，用于执行任务。线程的创建、调度等细节均由子类实现。</p><figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">Executor</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">void</span> <span class="title">execute</span><span class="params">(Runnable command)</span></span>;</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure></li><li><p><code>ExecutorService</code> 继承并拓展了 <code>Executor</code> ，内部提供给了更全面的任务提交机制以及线程池关闭的方法。</p><figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">ExecutorService</span> <span class="keyword">extends</span> <span class="title">Executor</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">void</span> <span class="title">shutdown</span><span class="params">()</span></span>;</span><br><span class="line"></span><br><span class="line"> <span class="function">List<Runnable> <span class="title">shutdownNow</span><span class="params">()</span></span>;</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">boolean</span> <span class="title">isShutdown</span><span class="params">()</span></span>;</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">boolean</span> <span class="title">isTerminated</span><span class="params">()</span></span>;</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">boolean</span> <span class="title">awaitTermination</span><span class="params">(<span class="keyword">long</span> timeout, TimeUnit unit)</span></span></span><br><span class="line"><span class="function"> <span class="keyword">throws</span> InterruptedException</span>;</span><br><span class="line"></span><br><span class="line"> <T> <span class="function">Future<T> <span class="title">submit</span><span class="params">(Callable<T> task)</span></span>;</span><br><span class="line"></span><br><span class="line"> <T> <span class="function">Future<T> <span class="title">submit</span><span class="params">(Runnable task, T result)</span></span>;</span><br><span class="line"></span><br><span class="line"> Future<?> submit(Runnable task);</span><br><span class="line"></span><br><span class="line"> <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)</span><br><span class="line"> <span class="keyword">throws</span> InterruptedException;</span><br><span class="line"></span><br><span class="line"> <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,</span><br><span class="line"> <span class="keyword">long</span> timeout, TimeUnit unit)</span><br><span class="line"> <span class="keyword">throws</span> InterruptedException;</span><br><span class="line"></span><br><span class="line"> <T> <span class="function">T <span class="title">invokeAny</span><span class="params">(Collection<? extends Callable<T>> tasks)</span></span></span><br><span class="line"><span class="function"> <span class="keyword">throws</span> InterruptedException, ExecutionException</span>;</span><br><span class="line"></span><br><span class="line"> <T> <span class="function">T <span class="title">invokeAny</span><span class="params">(Collection<? extends Callable<T>> tasks,</span></span></span><br><span class="line"><span class="function"><span class="params"> <span class="keyword">long</span> timeout, TimeUnit unit)</span></span></span><br><span class="line"><span class="function"> <span class="keyword">throws</span> InterruptedException, ExecutionException, TimeoutException</span>;</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure></li></ul><a id="more"></a><ul><li><p><code>ThreadPoolExecutor</code> 是 <code>ExecuteService</code> 的默认实现，所谓的线程池机制也大多封装在此类当中。</p></li><li><p><code>ScheduleExecutorService</code> 继承自 <code>ExecutorService</code> ，增加了定时任务相关方法。</p><figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">ScheduledExecutorService</span> <span class="keyword">extends</span> <span class="title">ExecutorService</span> </span>{</span><br><span class="line"> <span class="keyword">public</span> ScheduledFuture<?> schedule(Runnable command,</span><br><span class="line"> <span class="keyword">long</span> delay, TimeUnit unit);</span><br><span class="line"></span><br><span class="line"> <span class="keyword">public</span> <V> <span class="function">ScheduledFuture<V> <span class="title">schedule</span><span class="params">(Callable<V> callable,</span></span></span><br><span class="line"><span class="function"><span class="params"> <span class="keyword">long</span> delay, TimeUnit unit)</span></span>;</span><br><span class="line"></span><br><span class="line"> <span class="keyword">public</span> ScheduledFuture<?> scheduleAtFixedRate(Runnable command,</span><br><span class="line"> <span class="keyword">long</span> initialDelay,</span><br><span class="line"> <span class="keyword">long</span> period,</span><br><span class="line"> TimeUnit unit);</span><br><span class="line"></span><br><span class="line"> <span class="keyword">public</span> ScheduledFuture<?> scheduleWithFixedDelay(Runnable command,</span><br><span class="line"> <span class="keyword">long</span> initialDelay,</span><br><span class="line"> <span class="keyword">long</span> delay,</span><br><span class="line"> TimeUnit unit);</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure></li><li><p><code>ScheduleThreadPoolExecutor</code> 继承自 <code>ThreadPoolExecutor</code> ，并实现了 <code>ScheduleExecutorService</code> 接口。</p></li><li><p><code>ForkJoinPool</code> 是一种支持分解的线程池，一般配合可分解任务接口 <code>ForkJoinTask</code> 来使用。</p></li></ul><h5 id="如何创建线程池"><a href="#如何创建线程池" class="headerlink" title="如何创建线程池"></a>如何创建线程池</h5><blockquote><p>为了方便开发者可以更方便的使用线程池，<code>JDK</code> 中提供了一个创建线程池的工程类（<code>Executors</code> ，不过此方法在阿里Java开发手册中严禁使用，这是后话），在 <code>Executors</code> 中定义了多个静态方法用来创建不同配置的线程池，常见的有以下几种。</p></blockquote><ul><li><p><strong>newSingleThreadExecutor</strong></p><figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> ExecutorService <span class="title">newSingleThreadExecutor</span><span class="params">()</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">new</span> FinalizableDelegatedExecutorService</span><br><span class="line"> (<span class="keyword">new</span> ThreadPoolExecutor(<span class="number">1</span>, <span class="number">1</span>,</span><br><span class="line"> <span class="number">0L</span>, TimeUnit.MILLISECONDS,</span><br><span class="line"> <span class="keyword">new</span> LinkedBlockingQueue<Runnable>()));</span><br><span class="line"> }</span><br></pre></td></tr></tbody></table></figure><p>用来创建一个单线程的线程池，它只会用唯一的工作线程来执行任务，保证所有任务按照先进先出的顺序来执行任务。</p><figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">ThreadPoolTest</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String[] args)</span> </span>{</span><br><span class="line"> newSingleThreadPool();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">newSingleThreadPool</span><span class="params">()</span> </span>{</span><br><span class="line"> ExecutorService threadPool = Executors.newSingleThreadExecutor();</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> index = <span class="number">0</span>; index < <span class="number">10</span>; index++) {</span><br><span class="line"> <span class="keyword">final</span> <span class="keyword">int</span> taskId = index;</span><br><span class="line"> threadPool.submit(<span class="keyword">new</span> Runnable() {</span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">run</span><span class="params">()</span> </span>{</span><br><span class="line"> System.out.println(<span class="string">"当前线程："</span> + Thread.currentThread().getName() + <span class="string">"，当前任务ID："</span> + taskId);</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> Thread.sleep(<span class="number">1000</span>);</span><br><span class="line"> } <span class="keyword">catch</span> (InterruptedException e) {</span><br><span class="line"> e.printStackTrace();</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> });</span><br><span class="line"> }</span><br><span class="line"> threadPool.shutdown();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>执行结果输出可以看出 <code>Task</code> 始终在同一个线程中被执行的：</p><p><img src="https://s1.ax1x.com/2020/05/21/YbMbo4.jpg" alt="YbMbo4.jpg"></p></li><li><p><strong>newCachedThreadPool</strong></p><figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> ExecutorService <span class="title">newCachedThreadPool</span><span class="params">()</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">new</span> ThreadPoolExecutor(<span class="number">0</span>, Integer.MAX_VALUE,</span><br><span class="line"> <span class="number">60L</span>, TimeUnit.SECONDS,</span><br><span class="line"> <span class="keyword">new</span> SynchronousQueue<Runnable>());</span><br><span class="line"> }</span><br></pre></td></tr></tbody></table></figure><p>用来创建一个可缓存的线程池，如果线程池长度超过处理需要，可灵活回收空闲线程，如果没有可回收的，则新建线程。</p><figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">ThreadPoolTest</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String[] args)</span> </span>{</span><br><span class="line"> newSingleThreadPool();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">newCacheThreadPool</span><span class="params">()</span> </span>{</span><br><span class="line"> ExecutorService threadPool = Executors.newCachedThreadPool();</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> index = <span class="number">0</span>; index < <span class="number">10</span>; index++) {</span><br><span class="line"> <span class="keyword">final</span> <span class="keyword">int</span> taskId = index;</span><br><span class="line"> threadPool.submit(<span class="keyword">new</span> Runnable() {</span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">run</span><span class="params">()</span> </span>{</span><br><span class="line"> System.out.println(<span class="string">"当前线程："</span> + Thread.currentThread().getName() + <span class="string">"，当前任务ID："</span> + taskId);</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> Thread.sleep(<span class="number">1000</span>);</span><br><span class="line"> } <span class="keyword">catch</span> (InterruptedException e) {</span><br><span class="line"> e.printStackTrace();</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> });</span><br><span class="line"> }</span><br><span class="line"> threadPool.shutdown();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>执行输出如下：</p><p><img src="https://s1.ax1x.com/2020/05/21/Yb34NF.jpg" alt="Yb34NF.jpg"></p><p>可以看到新增了10条线程进行执行任务，不是说会缓存吗？来改下代码看看另外的执行情形，我们在每个任务提交前都先休眠2秒钟：</p><figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="function"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">newCacheThreadPool</span><span class="params">()</span> </span>{</span><br><span class="line"> ExecutorService threadPool = Executors.newCachedThreadPool();</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> index = <span class="number">0</span>; index < <span class="number">10</span>; index++) {</span><br><span class="line"> <span class="keyword">final</span> <span class="keyword">int</span> taskId = index;</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> Thread.sleep(<span class="number">2000</span>);</span><br><span class="line"> } <span class="keyword">catch</span> (InterruptedException e) {</span><br><span class="line"> e.printStackTrace();</span><br><span class="line"> }</span><br><span class="line"> threadPool.submit(<span class="keyword">new</span> Runnable() {</span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">run</span><span class="params">()</span> </span>{</span><br><span class="line"> System.out.println(<span class="string">"当前线程："</span> + Thread.currentThread().getName() + <span class="string">"，当前任务ID："</span> + taskId);</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> Thread.sleep(<span class="number">1000</span>);</span><br><span class="line"> } <span class="keyword">catch</span> (InterruptedException e) {</span><br><span class="line"> e.printStackTrace();</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> });</span><br><span class="line"> }</span><br><span class="line"> threadPool.shutdown();</span><br><span class="line"> }</span><br></pre></td></tr></tbody></table></figure><p>执行输出如下：</p><p><img src="https://s1.ax1x.com/2020/05/21/YbGDQs.jpg" alt="YbGDQs.jpg"></p><p>可以看到，第一次创建的线程被复用了，这是因为我们执行的任务所需时间是1秒，然后我们在进行下次任务的时候是每隔2秒，上次的任务早就执行完成了，所以线程1已经处于空闲状态，可以复用执行任务。</p></li><li><p><strong>newFixedThreadPool</strong></p><figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> ExecutorService <span class="title">newFixedThreadPool</span><span class="params">(<span class="keyword">int</span> nThreads)</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">new</span> ThreadPoolExecutor(nThreads, nThreads,</span><br><span class="line"> <span class="number">0L</span>, TimeUnit.MILLISECONDS,</span><br><span class="line"> <span class="keyword">new</span> LinkedBlockingQueue<Runnable>());</span><br><span class="line"> }</span><br></pre></td></tr></tbody></table></figure><p>创建一个固定数量的、可重用的线程池</p><figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">ThreadPoolTest</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String[] args)</span> </span>{</span><br><span class="line"> newSingleThreadPool();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">newCacheThreadPool</span><span class="params">()</span> </span>{</span><br><span class="line"> ExecutorService threadPool = Executors.newFixedThreadPool(<span class="number">5</span>);</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> index = <span class="number">0</span>; index < <span class="number">10</span>; index++) {</span><br><span class="line"> <span class="keyword">final</span> <span class="keyword">int</span> taskId = index;</span><br><span class="line"> threadPool.submit(<span class="keyword">new</span> Runnable() {</span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">run</span><span class="params">()</span> </span>{</span><br><span class="line"> System.out.println(<span class="string">"当前线程："</span> + Thread.currentThread().getName() + <span class="string">"，当前任务ID："</span> + taskId);</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> Thread.sleep(<span class="number">1000</span>);</span><br><span class="line"> } <span class="keyword">catch</span> (InterruptedException e) {</span><br><span class="line"> e.printStackTrace();</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> });</span><br><span class="line"> }</span><br><span class="line"> threadPool.shutdown();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>执行输出如下：</p><p><a href="https://imgchr.com/i/YbJ0AK" target="_blank" rel="noopener"><img src="https://s1.ax1x.com/2020/05/21/YbJ0AK.jpg" alt="YbJ0AK.jpg"></a></p><p>上面的代码创建了一个固定数量为5的线程池，虽然提交了10个任务，但是只会在这5个线程池进行分配执行。</p></li><li><p><strong>newScheduledThreadPool</strong></p><figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> ScheduledExecutorService <span class="title">newScheduledThreadPool</span><span class="params">(<span class="keyword">int</span> corePoolSize)</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">new</span> ScheduledThreadPoolExecutor(corePoolSize);</span><br><span class="line"> }</span><br></pre></td></tr></tbody></table></figure><p>创建一个定时线程池，支持定时及周期性任务执行。</p></li></ul><script> document.querySelectorAll('.github-emoji') .forEach(el => { if (!el.dataset.src) { return; } const img = document.createElement('img'); img.style = 'display:none !important;'; img.src = el.dataset.src; img.addEventListener('error', () => { img.remove(); el.style.color = 'inherit'; el.style.backgroundImage = 'none'; el.style.background = 'none'; }); img.addEventListener('load', () => { img.remove(); }); document.body.appendChild(img); }); </script>]]></content>
<summary type="html">
<h5 id="线程池体系"><a href="#线程池体系" class="headerlink" title="线程池体系"></a>线程池体系</h5><p><img src="https://s1.ax1x.com/2020/05/21/YbAtat.png" alt="YbAtat.png"></p>
<ul>
<li><p><code>Executor</code> 作为线程池最顶层的接口，它里面只有一个 <code>execute</code> 方法，用于执行任务。线程的创建、调度等细节均由子类实现。</p>
<figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">Executor</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">void</span> <span class="title">execute</span><span class="params">(Runnable command)</span></span>;</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure>
</li>
<li><p><code>ExecutorService</code> 继承并拓展了 <code>Executor</code> ，内部提供给了更全面的任务提交机制以及线程池关闭的方法。</p>
<figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">ExecutorService</span> <span class="keyword">extends</span> <span class="title">Executor</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">void</span> <span class="title">shutdown</span><span class="params">()</span></span>;</span><br><span class="line"></span><br><span class="line"> <span class="function">List&lt;Runnable&gt; <span class="title">shutdownNow</span><span class="params">()</span></span>;</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">boolean</span> <span class="title">isShutdown</span><span class="params">()</span></span>;</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">boolean</span> <span class="title">isTerminated</span><span class="params">()</span></span>;</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">boolean</span> <span class="title">awaitTermination</span><span class="params">(<span class="keyword">long</span> timeout, TimeUnit unit)</span></span></span><br><span class="line"><span class="function"> <span class="keyword">throws</span> InterruptedException</span>;</span><br><span class="line"></span><br><span class="line"> &lt;T&gt; <span class="function">Future&lt;T&gt; <span class="title">submit</span><span class="params">(Callable&lt;T&gt; task)</span></span>;</span><br><span class="line"></span><br><span class="line"> &lt;T&gt; <span class="function">Future&lt;T&gt; <span class="title">submit</span><span class="params">(Runnable task, T result)</span></span>;</span><br><span class="line"></span><br><span class="line"> Future&lt;?&gt; submit(Runnable task);</span><br><span class="line"></span><br><span class="line"> &lt;T&gt; List&lt;Future&lt;T&gt;&gt; invokeAll(Collection&lt;? extends Callable&lt;T&gt;&gt; tasks)</span><br><span class="line"> <span class="keyword">throws</span> InterruptedException;</span><br><span class="line"></span><br><span class="line"> &lt;T&gt; List&lt;Future&lt;T&gt;&gt; invokeAll(Collection&lt;? extends Callable&lt;T&gt;&gt; tasks,</span><br><span class="line"> <span class="keyword">long</span> timeout, TimeUnit unit)</span><br><span class="line"> <span class="keyword">throws</span> InterruptedException;</span><br><span class="line"></span><br><span class="line"> &lt;T&gt; <span class="function">T <span class="title">invokeAny</span><span class="params">(Collection&lt;? extends Callable&lt;T&gt;&gt; tasks)</span></span></span><br><span class="line"><span class="function"> <span class="keyword">throws</span> InterruptedException, ExecutionException</span>;</span><br><span class="line"></span><br><span class="line"> &lt;T&gt; <span class="function">T <span class="title">invokeAny</span><span class="params">(Collection&lt;? extends Callable&lt;T&gt;&gt; tasks,</span></span></span><br><span class="line"><span class="function"><span class="params"> <span class="keyword">long</span> timeout, TimeUnit unit)</span></span></span><br><span class="line"><span class="function"> <span class="keyword">throws</span> InterruptedException, ExecutionException, TimeoutException</span>;</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure>
</li>
</ul>
</summary>
<category term="Java" scheme="https://keee.top/categories/Java/"/>
<category term="多线程" scheme="https://keee.top/tags/%E5%A4%9A%E7%BA%BF%E7%A8%8B/"/>
</entry>
<entry>
<title>Jenkins自动化构建Android</title>
<link href="https://keee.top/2020/05227251.html"/>
<id>https://keee.top/2020/05227251.html</id>
<published>2020-05-22T10:05:53.000Z</published>
<updated>2020-05-22T10:05:53.000Z</updated>
<content type="html"><![CDATA[<blockquote><p>基于 Mac 环境，其它环境类似操作</p></blockquote><h4 id="Jenkins-安装"><a href="#Jenkins-安装" class="headerlink" title="Jenkins 安装"></a>Jenkins 安装</h4><ul><li><p>官网下载地址： <a href="https://jenkins.io/zh/download/" target="_blank" rel="noopener">https://jenkins.io/zh/download/</a></p></li><li><p>安装完成后自动跳转网页进行初始化设置</p><p><a href="https://imgchr.com/i/YBIckQ" target="_blank" rel="noopener"><img src="https://s1.ax1x.com/2020/05/14/YBIckQ.png" alt="YBIckQ.png"></a></p><a id="more"></a></li><li><p>找到该目录，改文件夹下是默认锁定不能读写的，可以更改权限，改成可读写就可以进入查看上面的文件了</p><p><a href="https://imgchr.com/i/YB7GwT" target="_blank" rel="noopener"><img src="https://s1.ax1x.com/2020/05/14/YB7GwT.png" alt="YB7GwT.png"></a></p></li></ul><p> <a href="https://imgchr.com/i/YB7wlR" target="_blank" rel="noopener"><img src="https://s1.ax1x.com/2020/05/14/YB7wlR.png" alt="YB7wlR.png"></a></p><ul><li><p>除了以上方法还有一种直接命令行查看的方法，输入以下命令键入电脑密码后进行查看密码</p><figure class="highlight shell"><table><tbody><tr><td class="code"><pre><span class="line">sudo cat /Users/Shared/Jenkins/Home/secrets/initialAdminPassword</span><br></pre></td></tr></tbody></table></figure></li></ul><h4 id="Jenkins-配置"><a href="#Jenkins-配置" class="headerlink" title="Jenkins 配置"></a>Jenkins 配置</h4><ul><li><p>安装完成自动跳转网页配置</p><p><img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583892762685-d64b5622-9877-44d3-8d9b-aed8cb4d8204.png#align=left&display=inline&height=402&margin=%5Bobject%20Object%5D&originHeight=534&originWidth=991&size=0&status=done&style=stroke&width=746" alt=""></p></li><li><p>直接选择安装推荐的插件即可，当然你想自己选择安装哪些插件也行，那就选择左边的进行自定义安装，选择后就是漫长的等待下载插件安装过程，插件安装失败可以重试多几次╮(￣▽￣)╭</p><p><img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583892815909-eb7262fa-f790-41d7-8041-bb6a2a34e259.png#align=left&display=inline&height=467&margin=%5Bobject%20Object%5D&originHeight=620&originWidth=990&size=0&status=done&style=stroke&width=746" alt=""></p></li></ul><ul><li><p>插件安装完成后，创建用户，也可以直接继续使用 admin 用户进行管理</p><p><img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583892867202-c22b9fac-2a67-4edc-aad2-f028dfecd8ff.png#align=left&display=inline&height=718&margin=%5Bobject%20Object%5D&originHeight=954&originWidth=991&size=0&status=done&style=stroke&width=746" alt=""></p></li></ul><ul><li><p>创建 <code>URL</code>，<code>localhost</code> 可以改为本机 <code>ip</code> 地址</p><p><img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583892925715-3cce9aa0-fd75-4055-8306-fa909b34d19e.png#align=left&display=inline&height=271&margin=%5Bobject%20Object%5D&originHeight=359&originWidth=989&size=0&status=done&style=stroke&width=746" alt=""></p></li></ul><ul><li><p>初始化完成</p><p><img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583892944805-1740edca-42ca-4051-93d1-0c720068beed.png#align=left&display=inline&height=284&margin=%5Bobject%20Object%5D&originHeight=377&originWidth=991&size=0&status=done&style=stroke&width=746" alt=""></p></li></ul><p> <img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583892977396-c1dff7a2-85b0-43ee-978e-f454191548a5.png#align=left&display=inline&height=532&margin=%5Bobject%20Object%5D&originHeight=532&originWidth=684&size=0&status=done&style=stroke&width=684" alt=""></p><ul><li><p>插件管理</p><p><img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583893005678-fe69e919-7bf9-49d6-899e-932d7ba5a2b5.png#align=left&display=inline&height=369&margin=%5Bobject%20Object%5D&originHeight=661&originWidth=1336&size=0&status=done&style=stroke&width=746" alt=""></p></li></ul><ul><li><p>【Git Parameter】插件，git 仓库的参数，例如分支选择 </p><p><img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583893087500-119cfa61-45da-4df4-a392-644bc8242141.png#align=left&display=inline&height=102&margin=%5Bobject%20Object%5D&originHeight=216&originWidth=1585&size=0&status=done&style=stroke&width=746" alt=""></p></li></ul><ul><li><p>【Build Name and Description Setter】插件，设置构建历史描述信息，例如可是设置描述显示二维码</p></li><li><p>【Upload to pgyer】插件，蒲公英上传插件，上传到外网，二维码扫码安装</p></li><li><p>更改设置显示富文本</p><p><img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583898796234-c02a69d0-33b0-45f2-8e34-5770579f3eeb.png#align=left&display=inline&height=250&margin=%5Bobject%20Object%5D&originHeight=367&originWidth=1093&size=0&status=done&style=stroke&width=746" alt=""></p></li></ul><p> <img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583898807937-c94ac540-93aa-4f28-8129-425a720c7de7.png#align=left&display=inline&height=478&margin=%5Bobject%20Object%5D&originHeight=655&originWidth=1022&size=0&status=done&style=stroke&width=746" alt=""></p><ul><li><p>修改默认的构建目录，该文件跟上面一开始的初始化密码文件在一起的</p><p><img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583898827768-ef59b5ac-21bd-4424-ae85-bb85020ee014.png#align=left&display=inline&height=374&margin=%5Bobject%20Object%5D&originHeight=374&originWidth=413&size=0&status=done&style=stroke&width=413" alt=""></p></li></ul><p> <img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583898875162-c82044c6-a324-4204-b65d-2a36d5beb4b4.png#align=left&display=inline&height=126&margin=%5Bobject%20Object%5D&originHeight=186&originWidth=1102&size=0&status=done&style=stroke&width=746" alt=""></p><p> 修改成你所想修改的目录即可，只需更改前半部分，后面的变量不需要更改，是根据项目自动生成文件夹的</p><p> <img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583898894960-8d7a4373-ab4c-4961-9196-d094306ff5d7.png#align=left&display=inline&height=57&margin=%5Bobject%20Object%5D&originHeight=87&originWidth=1139&size=0&status=done&style=stroke&width=746" alt=""></p><p> 修改完成后需要重新启动 Jenkins 加载配置</p> <figure class="highlight http"><table><tbody><tr><td class="code"><pre><span class="line"><span class="attribute">http://localhost:8080/reload</span></span><br></pre></td></tr></tbody></table></figure><ul><li><p>配置 <code>ANDROID_HOME</code></p><p><img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583899082207-c053f743-b830-4ada-8450-5802bfd089f7.png#align=left&display=inline&height=285&margin=%5Bobject%20Object%5D&originHeight=371&originWidth=972&size=0&status=done&style=stroke&width=746" alt=""></p></li></ul><p> <img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583903517381-e23ee694-043e-4b68-a87f-4768c0655433.png#align=left&display=inline&height=285&margin=%5Bobject%20Object%5D&originHeight=371&originWidth=972&size=0&status=done&style=stroke&width=746" alt=""></p><p> <img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583904961151-1d021923-64a7-4a43-a20f-47657591958e.png#align=left&display=inline&height=200&margin=%5Bobject%20Object%5D&originHeight=276&originWidth=1027&size=0&status=done&style=stroke&width=746" alt=""></p><ul><li><p>配置 Git，填写 Mac 系统安装的地址</p><p><img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583905021439-4e8aff43-4258-4d03-81ca-2fa9bc939e91.png#align=left&display=inline&height=464&margin=%5Bobject%20Object%5D&originHeight=546&originWidth=878&size=0&status=done&style=stroke&width=746" alt=""></p></li></ul><h4 id="项目配置"><a href="#项目配置" class="headerlink" title="项目配置"></a>项目配置</h4><ul><li><p>新建项目</p><p><img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583905073512-a9a3aea3-e9ad-4d8d-9bba-bd91b51de139.png#align=left&display=inline&height=283&margin=%5Bobject%20Object%5D&originHeight=283&originWidth=732&size=0&status=done&style=stroke&width=732" alt=""></p></li></ul><p> <img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583905202422-b3965a29-939a-4ac5-8d21-05e7b0c88f9b.png#align=left&display=inline&height=327&margin=%5Bobject%20Object%5D&originHeight=362&originWidth=826&size=0&status=done&style=stroke&width=746" alt=""></p><ul><li><p>参数化构建</p><p><img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583905490920-bf9112aa-d17b-4a55-8a4e-ef613be3d6f4.png#align=left&display=inline&height=514&margin=%5Bobject%20Object%5D&originHeight=514&originWidth=1446&size=0&status=done&style=stroke&width=1446" alt=""></p></li></ul><p> <img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583905506494-59ff145b-2ed1-4abb-a9fa-e2800fda8897.png#align=left&display=inline&height=808&margin=%5Bobject%20Object%5D&originHeight=808&originWidth=769&size=0&status=done&style=stroke&width=769" alt=""></p><ul><li><p>添加 <code>Git</code> 仓库，添加仓库的凭证</p><p><img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583905535995-f8e160d4-a40a-4b87-b7e9-70c114cc861b.png#align=left&display=inline&height=534&margin=%5Bobject%20Object%5D&originHeight=544&originWidth=760&size=0&status=done&style=stroke&width=746" alt=""></p></li></ul><p> <img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583905553680-862d4f99-a67f-4b6a-9cff-e507ff332a6b.png#align=left&display=inline&height=529&margin=%5Bobject%20Object%5D&originHeight=529&originWidth=681&size=0&status=done&style=stroke&width=681" alt=""></p><p> <img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583905565642-8c131664-d454-46d5-a7b0-6af778236dfc.png#align=left&display=inline&height=455&margin=%5Bobject%20Object%5D&originHeight=604&originWidth=990&size=0&status=done&style=stroke&width=746" alt=""></p><blockquote><p> <code>${Branch}</code> 是前面步骤 <code>Git Parameter</code> 定义分支参数。</p></blockquote><ul><li><p>选择 Shell 命令构建</p><p><a href="https://imgchr.com/i/YBqO9e" target="_blank" rel="noopener"><img src="https://s1.ax1x.com/2020/05/14/YBqO9e.png" alt="YBqO9e.png"></a></p></li></ul><blockquote><p>命令如下：</p></blockquote> <figure class="highlight shell"><table><tbody><tr><td class="code"><pre><span class="line"><span class="meta">#</span><span class="bash">!/bin/bash</span></span><br><span class="line"></span><br><span class="line">this_dir=`pwd`</span><br><span class="line">project_name="/QMEasy"</span><br><span class="line">project_full_dir="${this_dir}${project_name}"</span><br><span class="line">build_type=$BuildType</span><br><span class="line">build_type_debug="Debug"</span><br><span class="line">build_type_release="Release"</span><br><span class="line"></span><br><span class="line">echo '***********************************************.开始执行.*********************************************'</span><br><span class="line">cd $project_full_dir</span><br><span class="line">this_dir=`pwd`</span><br><span class="line">echo ">当前目录：${this_dir}"</span><br><span class="line"></span><br><span class="line">echo '***********************************************gradle 版本********************************************'</span><br><span class="line"><span class="meta">$</span><span class="bash">this_dir/gradlew -v</span></span><br><span class="line">echo '*****************************************************************************************************'</span><br><span class="line"></span><br><span class="line">echo '************************************************当前构建环境*******************************************'</span><br><span class="line">if [ "$build_type" = "$build_type_debug" ]</span><br><span class="line">then</span><br><span class="line"> echo ">测试环境"</span><br><span class="line">elif [ "$build_type" = "$build_type_release" ]</span><br><span class="line">then</span><br><span class="line"> echo ">正式环境"</span><br><span class="line">else</span><br><span class="line"> echo ">环境配置错误，已退出构建..."</span><br><span class="line"> exit</span><br><span class="line">fi</span><br><span class="line">echo '*****************************************************************************************************'</span><br><span class="line"></span><br><span class="line">echo '************************************************当前项目分支*******************************************'</span><br><span class="line">echo ">${Branch}"</span><br><span class="line">echo '*****************************************************************************************************'</span><br><span class="line"></span><br><span class="line">echo ">clean 项目..."</span><br><span class="line"><span class="meta">$</span><span class="bash">this_dir/gradlew clean</span></span><br><span class="line">echo '*****************************************************************************************************'</span><br><span class="line"></span><br><span class="line">echo ">开始构建..."</span><br><span class="line"><span class="meta">$</span><span class="bash">this_dir/gradlew assemble<span class="variable">$BuildType</span></span></span><br><span class="line">echo '*****************************************************************************************************'</span><br><span class="line"></span><br><span class="line">apk_dest_dir=/Volumes/数据/Jenkins/APK/分期易/</span><br><span class="line">echo ">移动apk到指定目录 ---> $apk_dest_dir"</span><br><span class="line">rm -rf $apk_dest_dir</span><br><span class="line">mkdir $apk_dest_dir</span><br><span class="line">apk_src_dir=${WORKSPACE}$project_name/app/build/outputs/apk/${BuildType}/*.apk</span><br><span class="line">mv -f $apk_src_dir $apk_dest_dir</span><br><span class="line">echo ">移动完成..."</span><br><span class="line">echo '*****************************************************************************************************'</span><br><span class="line"></span><br><span class="line">echo ">构建结束，开始上传到蒲公英..."</span><br><span class="line">echo '*****************************************************************************************************'</span><br></pre></td></tr></tbody></table></figure><ul><li><p>配置蒲公英上传</p><blockquote><p>key可以在蒲公英说明找到，scandir指的是扫描上传的apk目录，Build Description是构建后的描述信息，这里我配置的是本地的共享目录，img用的是蒲公英的二维码。</p></blockquote><p><a href="https://imgchr.com/i/YBLk9g" target="_blank" rel="noopener"><img src="https://s1.ax1x.com/2020/05/14/YBLk9g.png" alt="YBLk9g.png"></a></p></li></ul><ul><li><p>蒲公英key的获取地址 <a href="https://www.pgyer.com/doc/view/api" target="_blank" rel="noopener">https://www.pgyer.com/doc/view/api</a></p></li><li><p>配置完成后可以开始构建项目</p><p><img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583905961338-336b6358-6353-4a4c-9238-d95648bf5c2f.png#align=left&display=inline&height=453&margin=%5Bobject%20Object%5D&originHeight=499&originWidth=821&size=0&status=done&style=stroke&width=746" alt=""></p></li></ul><p> <img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583905980688-13435365-360f-4f8a-aa59-df5868fb0f61.png#align=left&display=inline&height=326&margin=%5Bobject%20Object%5D&originHeight=326&originWidth=472&size=0&status=done&style=stroke&width=472" alt=""></p><ul><li><p>对应的构建输出信息可以查看对应项目的控制台输出</p><p><a href="https://imgchr.com/i/YBLf58" target="_blank" rel="noopener"><img src="https://s1.ax1x.com/2020/05/14/YBLf58.png" alt="YBLf58.png"></a></p></li></ul><h4 id="局域网文件共享"><a href="#局域网文件共享" class="headerlink" title="局域网文件共享"></a>局域网文件共享</h4><blockquote><p>利用 Mac 本身自带的 Apache 进行局域网文件共享，无需传到外网蒲公英等第三方</p></blockquote><ul><li><p>命令行输入 httpd -v 查看对应的版本信息</p><p><img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583906185585-a2e16188-7ee8-4f68-915a-d6ddbaed673a.png#align=left&display=inline&height=79&margin=%5Bobject%20Object%5D&originHeight=79&originWidth=312&size=0&status=done&style=none&width=312" alt=""></p></li><li><p>命令行输入 sudo apachectl start 启动服务，需要输入 Mac 的登录密码开启</p></li><li><p>浏览器 <a href="">http:/127.0.0.1</a> 进行访问，可以看到网页输出</p><p><img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583906185562-1a9f51c8-fce7-447b-a2bd-4655858bbf9a.png#align=left&display=inline&height=67&margin=%5Bobject%20Object%5D&originHeight=67&originWidth=139&size=0&status=done&style=none&width=139" alt=""></p></li><li><p>修改文件存放的目录</p></li><li><p>原始目录</p><p><img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583906185546-90cbe9d3-d390-4010-aeac-95c5769b23be.png#align=left&display=inline&height=342&margin=%5Bobject%20Object%5D&originHeight=376&originWidth=820&size=0&status=done&style=stroke&width=746" alt=""></p></li></ul><ul><li><p>配置文件目录</p><p><img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583906185577-4369f5f2-e7a3-49ab-9c3b-9e71ad7c8e2e.png#align=left&display=inline&height=379&margin=%5Bobject%20Object%5D&originHeight=379&originWidth=634&size=0&status=done&style=none&width=634" alt=""></p></li></ul><ul><li><p>打开该文件，查找 DocumentRoot 节点，修改为你需要的目录。</p></li><li><p>Root 节点下的文件类型也需要修改，然后输入命令 sudo apachectl restart 重启服务，再次访问 <a href="http://127.0.0.1" target="_blank" rel="noopener">http://127.0.0.1</a> 就会看到你刚才更改目录下的文件。</p><figure class="highlight html"><table><tbody><tr><td class="code"><pre><span class="line">DocumentRoot "/Volumes/文档/apk"</span><br><span class="line"><span class="tag"><<span class="name">Directory</span> "/<span class="attr">Volumes</span>/文档/<span class="attr">apk</span>"></span></span><br><span class="line"> Options Indexes FollowSymLinks Multiviews</span><br><span class="line"> MultiviewsMatch Any</span><br><span class="line"> AllowOverride All</span><br><span class="line"> Require all granted</span><br><span class="line"><span class="tag"></<span class="name">Directory</span>></span></span><br></pre></td></tr></tbody></table></figure><p><img src="https://cdn.nlark.com/yuque/0/2020/png/407428/1583906185615-623fa570-19f1-41cc-8a64-b645d5784ad6.png#align=left&display=inline&height=199&margin=%5Bobject%20Object%5D&originHeight=199&originWidth=378&size=0&status=done&style=none&width=378" alt=""></p></li><li><p>局域网访问直接输入 <a href="http://本机ip地址" target="_blank" rel="noopener">http://本机ip地址</a></p></li></ul><script> document.querySelectorAll('.github-emoji') .forEach(el => { if (!el.dataset.src) { return; } const img = document.createElement('img'); img.style = 'display:none !important;'; img.src = el.dataset.src; img.addEventListener('error', () => { img.remove(); el.style.color = 'inherit'; el.style.backgroundImage = 'none'; el.style.background = 'none'; }); img.addEventListener('load', () => { img.remove(); }); document.body.appendChild(img); }); </script>]]></content>
<summary type="html">
<blockquote>
<p>基于 Mac 环境，其它环境类似操作</p>
</blockquote>
<h4 id="Jenkins-安装"><a href="#Jenkins-安装" class="headerlink" title="Jenkins 安装"></a>Jenkins 安装</h4><ul>
<li><p>官网下载地址： <a href="https://jenkins.io/zh/download/" target="_blank" rel="noopener">https://jenkins.io/zh/download/</a></p>
</li>
<li><p>安装完成后自动跳转网页进行初始化设置</p>
<p><a href="https://imgchr.com/i/YBIckQ" target="_blank" rel="noopener"><img src="https://s1.ax1x.com/2020/05/14/YBIckQ.png" alt="YBIckQ.png"></a></p></li></ul>
</summary>
<category term="Android" scheme="https://keee.top/categories/Android/"/>
<category term="Jenkins" scheme="https://keee.top/tags/Jenkins/"/>
<category term="自动化" scheme="https://keee.top/tags/%E8%87%AA%E5%8A%A8%E5%8C%96/"/>
</entry>
<entry>
<title>Kotlin基础</title>
<link href="https://keee.top/2020/0522bfb2.html"/>
<id>https://keee.top/2020/0522bfb2.html</id>
<published>2020-05-22T10:05:53.000Z</published>
<updated>2020-05-22T10:05:53.000Z</updated>
<content type="html"><![CDATA[<h3 id="函数声明"><a href="#函数声明" class="headerlink" title="函数声明"></a>函数声明</h3><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="function"><span class="keyword">fun</span> <span class="title">max</span><span class="params">(a: <span class="type">Int</span>, b: <span class="type">Int</span>)</span></span>: <span class="built_in">Int</span> = <span class="keyword">if</span>(a>b) a <span class="keyword">else</span> b</span><br></pre></td></tr></tbody></table></figure><p>关键字<code>fun</code>，名称<code>max</code>，括号内的参数列表，先参数名，冒号后面是参数类型，括号后面的冒号跟着返回值类型，如果没有返回值就把冒号跟返回值类型直接去掉，<code>kotlin</code>里面<code>if</code>是有结果的表达式。</p><h3 id="变量声明"><a href="#变量声明" class="headerlink" title="变量声明"></a>变量声明</h3><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">val</span> a = <span class="number">1</span></span><br><span class="line"><span class="keyword">val</span> a: <span class="built_in">Int</span> = <span class="number">1</span></span><br><span class="line"><span class="keyword">var</span> b = <span class="number">2</span></span><br><span class="line"><span class="keyword">var</span> b: <span class="built_in">Int</span> = <span class="number">2</span></span><br></pre></td></tr></tbody></table></figure><p>声明变量的关键字有两个不可变引用<code>val</code>、可变引用<code>var</code>，默认情况下尽可能用<code>val</code>去声明变量，仅在必要的时候把变量声明为<code>var</code>，这样可以让你的代码更接近函数式编程风格。声明变量的时候可以显式的指定变量的类型，也可以直接隐藏去掉(如果已经可以推断出类型)</p><h3 id="字符串格式化模板"><a href="#字符串格式化模板" class="headerlink" title="字符串格式化模板"></a>字符串格式化模板</h3><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">val</span> name = <span class="string">"bob"</span></span><br><span class="line"><span class="keyword">val</span> sex = <span class="string">"男"</span></span><br><span class="line"><span class="keyword">val</span> age = <span class="number">100</span></span><br><span class="line">print(<span class="string">"<span class="subst">${name}</span>的性别为：<span class="variable">$sex</span>，年龄为：<span class="variable">$age</span>"</span>)</span><br><span class="line"></span><br><span class="line"><span class="comment">// 输出结果：bob的性别为：男，年龄为：100</span></span><br></pre></td></tr></tbody></table></figure><p>可以直接用<code>$</code>符号对变量进行引用，还可以用<code>${}</code>这种对表达式进行引用，就像刚才的例子那样，<code>name</code>可以换成表达式进行使用。</p><a id="more"></a><h3 id="类和属性"><a href="#类和属性" class="headerlink" title="类和属性"></a>类和属性</h3><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Person</span></span>(<span class="keyword">val</span> name: String)</span><br></pre></td></tr></tbody></table></figure><p>在<code>Java</code>中，声明一个<code>JavaBean</code>类的<code>Person</code>除了属性<code>name</code>外，一般还需要设置<code>setter</code>跟<code>getter</code>方法，在<code>Kotlin</code>中可以直接就像上面的例子那样就可以了，<code>Kotlin</code>中<code>public</code>是默认的可见性，可以忽略它，如果这个<code>bean</code>是不需要更改里面的属性的，上面的代码例子就已经完成了，如果需要像<code>Java</code>那样有<code>setter</code>方法对属性进行更改，那么可以把<code>val</code>改成<code>var</code>即可。</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Person</span></span>(<span class="keyword">var</span> name: String)</span><br></pre></td></tr></tbody></table></figure><p>我们还可以自定义类属性的访问器</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Person</span></span>(<span class="keyword">var</span> name: String) {</span><br><span class="line"> <span class="keyword">val</span> isMarried: <span class="built_in">Boolean</span></span><br><span class="line"> <span class="keyword">get</span>() = name == <span class="string">"Bob"</span></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>单独声明一个变量<code>isMarried</code>，然后在<code>get()</code>方法中对其进行判断返回。</p><h3 id="枚举类enum-class和when"><a href="#枚举类enum-class和when" class="headerlink" title="枚举类enum class和when"></a>枚举类<code>enum class</code>和<code>when</code></h3><h4 id="枚举类"><a href="#枚举类" class="headerlink" title="枚举类"></a>枚举类</h4><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">enum</span> <span class="class"><span class="keyword">class</span> <span class="title">MyColor</span> </span>{</span><br><span class="line"> RED, GREEN, BLUE</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><code>Kotlin</code>中用了<code>enum class</code>两个关键字来声明枚举类，我们还可以给枚举类声明属性和方法。</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">enum</span> <span class="class"><span class="keyword">class</span> <span class="title">MyColor</span></span>(<span class="keyword">val</span> r: <span class="built_in">Int</span>, <span class="keyword">val</span> g: <span class="built_in">Int</span>, <span class="keyword">val</span> b: <span class="built_in">Int</span>) {</span><br><span class="line"> RED(<span class="number">255</span>, <span class="number">0</span>, <span class="number">0</span>), GREEN(<span class="number">0</span>, <span class="number">255</span>, <span class="number">0</span>), BLUE(<span class="number">0</span>, <span class="number">0</span>, <span class="number">255</span>);</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">fun</span> <span class="title">rgb</span><span class="params">()</span></span> = (r * <span class="number">256</span> + g) * <span class="number">256</span> + b</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>然后可以使用该变量、方法</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line">MyColor.BLUE.rgb()</span><br></pre></td></tr></tbody></table></figure><h4 id="when"><a href="#when" class="headerlink" title="when"></a><code>when</code></h4><p><code>kotlin</code>中的<code>when</code>代替了<code>Java</code>中的<code>switch</code>，跟<code>if</code>一样，<code>when</code>也是一个有返回值的表达式</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="function"><span class="keyword">fun</span> <span class="title">getMyColor</span><span class="params">(color: <span class="type">MyColor</span>)</span></span> = <span class="keyword">when</span> (color) {</span><br><span class="line"> MyColor.RED -> <span class="string">"红色"</span></span><br><span class="line"> MyColor.GREEN -> <span class="string">"绿色"</span></span><br><span class="line"> MyColor.BLUE -> <span class="string">"蓝色"</span></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>对于分支还可以用逗号合并起来的，例如下面例子</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="function"><span class="keyword">fun</span> <span class="title">getMyColor</span><span class="params">(color: <span class="type">MyColor</span>)</span></span> = <span class="keyword">when</span> (color) {</span><br><span class="line"> MyColor.RED -> <span class="string">"红色"</span></span><br><span class="line"> MyColor.GREEN, MyColor.BLUE -> <span class="string">"绿色、蓝色"</span></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><code>when</code>还可以使用<code>else</code>作为分支，<code>when</code>的条件不像<code>Java</code>的<code>switch</code>只能使用枚举常量、字符串或者数字面值这种，<code>when</code>可以使用任何对象作为分支条件</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="function"><span class="keyword">fun</span> <span class="title">getMyColor</span><span class="params">(color: <span class="type">MyColor</span>)</span></span> = <span class="keyword">when</span> (color) {</span><br><span class="line"> setOf(MyColor.RED) -> <span class="string">"红色"</span></span><br><span class="line"> setOf(MyColor.GREEN, MyColor.BLUE) -> <span class="string">"绿色、蓝色混合"</span></span><br><span class="line"> <span class="keyword">else</span> -> <span class="string">"其它颜色混合"</span></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><code>when</code>还可以不带参数条件，分支条件结果为<code>true</code>或者<code>false</code>就行</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="function"><span class="keyword">fun</span> <span class="title">getMyColor</span><span class="params">(color: <span class="type">MyColor</span>)</span></span> = <span class="keyword">when</span> {</span><br><span class="line"> color == MyColor.RED -> <span class="string">"红色"</span></span><br><span class="line"> color == MyColor.GREEN || color == MyColor.BLUE -> <span class="string">"绿色、蓝色混合"</span></span><br><span class="line"> <span class="keyword">else</span> -> <span class="string">"其它颜色混合"</span></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><h3 id="智能转换，合并类型检查和转换"><a href="#智能转换，合并类型检查和转换" class="headerlink" title="智能转换，合并类型检查和转换"></a>智能转换，合并类型检查和转换</h3><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="function"><span class="keyword">fun</span> <span class="title">getTextViewText</span><span class="params">(cc : <span class="type">View</span>)</span></span>: String? {</span><br><span class="line"> <span class="keyword">if</span> (cc <span class="keyword">is</span> TextView) {</span><br><span class="line"> <span class="keyword">return</span> cc.text.toString()</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> <span class="literal">null</span></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>上面的例子中，在<code>if</code>中使用了<code>is</code>关键字进行类型判断跟转换，所以在条件内部中可以直接使用<code>TextView</code>的内部方法，相对于已经把<code>cc</code>转换为<code>TextView</code>了，另外<code>String?</code>是<code>Kotlin</code>表示可以为空的变量表达方法。</p><h3 id="迭代：while、for"><a href="#迭代：while、for" class="headerlink" title="迭代：while、for"></a>迭代：<code>while</code>、<code>for</code></h3><p>这个跟<code>Java</code>中基本上一致，没什么新内容。<code>for</code>迭代可以使用区间和数列，用<code>..</code>运算符表示区间，一个代表起始值，一个表示结束值：</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">val</span> oneToTen = <span class="number">1</span>..<span class="number">10</span></span><br></pre></td></tr></tbody></table></figure><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">for</span> (index <span class="keyword">in</span> <span class="number">1</span>..<span class="number">5</span>) {</span><br><span class="line"> print(index)</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">// 输出：1、2、3、4、5</span></span><br></pre></td></tr></tbody></table></figure><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">for</span> (index <span class="keyword">in</span> <span class="number">1</span> until <span class="number">5</span>) {</span><br><span class="line"> print(index)</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">// 输出：1、2、3、4</span></span><br></pre></td></tr></tbody></table></figure><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">for</span> (index <span class="keyword">in</span> <span class="number">5</span> downTo <span class="number">1</span>) {</span><br><span class="line"> print(index)</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">// 输出：5、4、3、2、1</span></span><br></pre></td></tr></tbody></table></figure><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">for</span> (index <span class="keyword">in</span> <span class="number">5</span> downTo <span class="number">1</span> step <span class="number">2</span>) {</span><br><span class="line"> print(index)</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">// 输出：5、3、1</span></span><br></pre></td></tr></tbody></table></figure><p><code>step</code>表示步长</p><h3 id="关键字in"><a href="#关键字in" class="headerlink" title="关键字in"></a>关键字<code>in</code></h3><p>使用<code>in</code>运算符来检查一个值是否在某个区间中或者它的逆运算<code>!in</code>检查这个值是否不在某个区间内。</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="function"><span class="keyword">fun</span> <span class="title">isLetter</span><span class="params">(c: <span class="type">Char</span>)</span></span> = c <span class="keyword">in</span> <span class="string">'a'</span>..<span class="string">'z'</span> || c <span class="keyword">in</span> <span class="string">'A'</span>..<span class="string">'Z'</span></span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">fun</span> <span class="title">isNotDigit</span><span class="params">(c: <span class="type">Char</span>)</span></span> = c <span class="keyword">in</span> <span class="string">'0'</span>..<span class="string">'9'</span></span><br></pre></td></tr></tbody></table></figure><h3 id="函数定义与调用"><a href="#函数定义与调用" class="headerlink" title="函数定义与调用"></a>函数定义与调用</h3><p><code>Kotlin</code>没有使用自己的集合类，用的是标准的<code>Java</code>集合类，使得<code>Kotlin</code>可以更好的与<code>Java</code>代码交互，下面例子创建一些基本的集合类。</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">val</span> <span class="keyword">set</span> = hashSetOf(<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>)</span><br><span class="line"><span class="keyword">val</span> list = listOf(<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>)</span><br><span class="line"><span class="keyword">val</span> map = hashMapOf(<span class="number">1</span> to <span class="string">"one"</span>, <span class="number">2</span> to <span class="string">"two"</span>, <span class="number">3</span> to <span class="string">"three"</span>)</span><br></pre></td></tr></tbody></table></figure><h3 id="顶层函数"><a href="#顶层函数" class="headerlink" title="顶层函数"></a>顶层函数</h3><p><code>Kotlin</code>可以定义顶层函数，创建一个名为<code>KtEx</code>的<code>kt</code>文件，直接创建函数：</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="function"><span class="keyword">fun</span> <span class="title">join</span><span class="params">(source: <span class="type">String</span>, suffix: <span class="type">String</span>)</span></span>: String {</span><br><span class="line"> <span class="keyword">return</span> source.plus(suffix)</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>在<code>kotlin</code>的其它地方就可以直接调用该<code>join</code>函数，如果是<code>Java</code>中调用的话，系统已经自动生成名为<code>KtExKt</code>的类去引用该静态方法，<code>KtExKt.join(source, suffix)</code></p><h3 id="扩展函数和属性"><a href="#扩展函数和属性" class="headerlink" title="扩展函数和属性"></a>扩展函数和属性</h3><p>扩展函数很简单，理论上来说，它就是一个类的成员函数，不过是定义在类的外部而已，<code>Kotlin</code>为我们定义了很多扩展函数，例如集合类<code>List</code>中有<code>last()、max()</code>等扩展函数。我们也可以自己自定义扩展函数，为String来扩展一个成员函数，获取<code>String</code>的最后一个字符返回</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">package</span> com.glimmer</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">fun</span> String.<span class="title">lastChar</span><span class="params">()</span></span>: <span class="built_in">Char</span> = <span class="keyword">get</span>(length - <span class="number">1</span>)</span><br></pre></td></tr></tbody></table></figure><p>然后我们就可以用<code>String</code>类型的变量直接调用该方法了，<code>Java</code>调用跟刚才一样</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="string">"abc"</span>.lastChar()</span><br></pre></td></tr></tbody></table></figure><figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line">KtExKt.lastChar(“abc”);</span><br></pre></td></tr></tbody></table></figure><p>在扩展函数中，可以直接访问被扩展的类的其它方法和属性，注意，扩展函数并不允许你打破它的封装性，跟在内部定义的方法不同的是，扩展函数不能访问私有的或者是受保护的成员。</p><h4 id="导入扩展函数"><a href="#导入扩展函数" class="headerlink" title="导入扩展函数"></a>导入扩展函数</h4><p>扩展函数有时候会有命名冲突，<code>Kotlin</code>支持用和导入类一样的语法来导入某个函数</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">import</span> com.glimmer.lastChar</span><br></pre></td></tr></tbody></table></figure><p>还可以导入全部</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">import</span> com.glimmer.*</span><br></pre></td></tr></tbody></table></figure><p>可以使用关键字<code>as</code>来修改导入的名称，后面就可以直接使用该名称来进行调用</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">import</span> com.glimmer.lastChar <span class="keyword">as</span> last</span><br><span class="line"></span><br><span class="line"><span class="string">"abc"</span>.last()</span><br></pre></td></tr></tbody></table></figure><h4 id="扩展属性"><a href="#扩展属性" class="headerlink" title="扩展属性"></a>扩展属性</h4><p>扩展属性提供了一种方法用来扩展类的<code>API</code>，可以用来访问属性，用的是属性语法而不是函数的语法，尽管它们被称为属性，但是它们可以没有任何状态，因为没有合适的地方来存储它。扩展属性跟扩展函数一样，也像接收者的一个普通的成员属性一样，这里必须定义<code>getter</code>函数，因为没有支持的字段，因此没有默认的<code>getter</code>实现，同理，初始化也不可可以的，因为没有地方存储初始值。</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">val</span> String.last: <span class="built_in">Char</span></span><br><span class="line"> <span class="keyword">get</span>() = <span class="keyword">get</span>(length - <span class="number">1</span>)</span><br></pre></td></tr></tbody></table></figure><p>然后我们就可以直接用它的扩展属性了</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="string">"abc"</span>.last</span><br></pre></td></tr></tbody></table></figure><p>如果是在<code>StringBuilder</code>上定义一个相同的属性，这就可以设置为<code>var</code>，因为<code>StringBuilder</code>的内容是可变的。</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">var</span> StringBuilder.lastChar: <span class="built_in">Char</span></span><br><span class="line"> <span class="keyword">get</span>() = <span class="keyword">get</span>(length - <span class="number">1</span>)</span><br><span class="line"> <span class="keyword">set</span>(filed) = setCharAt(length - <span class="number">1</span>, filed)</span><br></pre></td></tr></tbody></table></figure><h3 id="可变参数"><a href="#可变参数" class="headerlink" title="可变参数"></a>可变参数</h3><p>当你调用函数来创建一个列表的时候，可以传递任意个的参数给它进行初始化：</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">val</span> list = listOf(<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>)</span><br></pre></td></tr></tbody></table></figure><p>该函数在库中的声明是：</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="function"><span class="keyword">fun</span> <span class="type"><T></span> <span class="title">listOf</span><span class="params">(<span class="keyword">vararg</span> elements: <span class="type">T</span>)</span></span>: List<T> = {...}</span><br></pre></td></tr></tbody></table></figure><p>可以发现<code>Kotlin</code>中的可变参数关键字是<code>vararg</code></p><h3 id="中缀调用和解构声明"><a href="#中缀调用和解构声明" class="headerlink" title="中缀调用和解构声明"></a>中缀调用和解构声明</h3><p>我们可以使用<code>mapOf</code>函数来创建<code>map</code></p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">val</span> map = mapOf(<span class="number">1</span> to <span class="string">"one"</span>, <span class="number">2</span> to <span class="string">"two"</span>)</span><br></pre></td></tr></tbody></table></figure><p>以上代码中的关键字’to’不是内置的结构，而是一种特殊的函数调用，被称为中缀调用。<br>在中缀调用中，没有添加额外的分隔符，函数名称是直接放在目标对象名称和参数之间的，就像以下的两种调用方式，它们是等价的：</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="number">1</span> to <span class="string">"one"</span></span><br><span class="line"><span class="number">1</span>.to(<span class="string">"one"</span>)</span><br></pre></td></tr></tbody></table></figure><p>中缀调用可以与只有一个参数的函数一起使用，无论是普通的函数还是扩展函数，要允许使用中缀符号调用函数需要使用<code>infix</code>修饰符来标记，下面是一个简单的<code>to</code>函数的声明：</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">infix</span> <span class="function"><span class="keyword">fun</span> Any.<span class="title">to</span><span class="params">(other: <span class="type">Any</span>)</span></span> = Pair(<span class="keyword">this</span>, other)</span><br></pre></td></tr></tbody></table></figure><p>在<code>Koltin</code>中可以把一个对象赋值给多个变量，这种操作叫做解构声明。</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">val</span>(number, name) = <span class="number">1</span> to <span class="string">"one"</span></span><br><span class="line"><span class="comment">// 然后我们可以直接调用打印number跟name</span></span><br><span class="line">print(number)</span><br><span class="line">print(name)</span><br></pre></td></tr></tbody></table></figure><p>数据类会默认生成解构声明</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">data</span> <span class="class"><span class="keyword">class</span> <span class="title">Book</span></span>(<span class="keyword">var</span> name: String, <span class="keyword">var</span> price: <span class="built_in">Float</span>)</span><br></pre></td></tr></tbody></table></figure><p>然后就可以调用<code>Book</code>的解构声明<code>component1()</code>对应<code>name</code>，<code>component2()</code>对应<code>price</code><br>我们还可以为普通类自定义解构声明</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Book</span></span>(<span class="keyword">var</span> name: String, <span class="keyword">var</span> price: <span class="built_in">Float</span>) {</span><br><span class="line"> <span class="keyword">operator</span> <span class="function"><span class="keyword">fun</span> <span class="title">component1</span><span class="params">()</span></span>: String {</span><br><span class="line"> <span class="keyword">return</span> name</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">operator</span> <span class="function"><span class="keyword">fun</span> <span class="title">component2</span><span class="params">()</span></span>: <span class="built_in">Float</span> {</span><br><span class="line"> <span class="keyword">return</span> price</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><hr><h3 id="类、对象、接口"><a href="#类、对象、接口" class="headerlink" title="类、对象、接口"></a>类、对象、接口</h3><p><code>Kotlin</code>的类和接口与<code>Java</code>的还是有点区别的，例如<code>Kotlin</code>的接口是可以包含属性声明的，默认声明都是<code>final</code>和<code>public</code>，父类中的方法如果需要在子类中重写的话需要添加<code>open</code>关键字。嵌套的类默认不是内部类，也没有包含对其外部类的隐式引用。<code>kotlin</code>除了<code>public</code>、<code>protected</code>、<code>private</code>修饰符外，还新增了<code>internal</code>表示模块内部中可见修饰符，一个模块就是一组一起编译的<code>kotlin</code>文件。</p><h4 id="内部类和嵌套类：默认是嵌套类"><a href="#内部类和嵌套类：默认是嵌套类" class="headerlink" title="内部类和嵌套类：默认是嵌套类"></a>内部类和嵌套类：默认是嵌套类</h4><p>跟<code>Java</code>一样，在<code>Kotlin</code>中也可以在一个类中声明另一个类，但是<code>kotlin</code>的嵌套类不能访问外部类的实例，它并没有像<code>Java</code>那样包含了对外部类的隐式引用，除非你特别做出了要求，在<code>class</code>前面加上<code>inner</code>关键字声明这是一个内部类。</p><h4 id="密封类sealed"><a href="#密封类sealed" class="headerlink" title="密封类sealed"></a>密封类<code>sealed</code></h4><p>当我们使用<code>when</code>作为表达式来赋值的时候，我们必须提供一个else分支来处理没有其它任何分支能匹配的情况。</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="class"><span class="keyword">interface</span> <span class="title">Expr</span></span></span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Num</span></span>(<span class="keyword">val</span> value: <span class="built_in">Int</span>) : Expr</span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Sum</span></span>(<span class="keyword">val</span> left: Expr, <span class="keyword">val</span> right: Expr) : Expr</span><br></pre></td></tr></tbody></table></figure><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="function"><span class="keyword">fun</span> <span class="title">eval</span><span class="params">(e: <span class="type">Expr</span>)</span></span>: <span class="built_in">Int</span> = </span><br><span class="line"> <span class="keyword">when</span>(e) {</span><br><span class="line"> <span class="keyword">is</span> Num -> e.value</span><br><span class="line"> <span class="keyword">is</span> Sum -> eval(e.left) + eval(e.right)</span><br><span class="line"> <span class="keyword">else</span> -> -<span class="number">1</span></span><br><span class="line"> }</span><br></pre></td></tr></tbody></table></figure><p>加上密封类关键字后，<code>Kotlin</code>就会对可能创建的子类做出了一个的限制，所有的直接子类必须嵌套在父类中。</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">sealed</span> <span class="class"><span class="keyword">class</span> <span class="title">Expr</span> </span>{</span><br><span class="line"> <span class="class"><span class="keyword">class</span> <span class="title">Num</span></span>(<span class="keyword">val</span> value: <span class="built_in">Int</span>) : Expr()</span><br><span class="line"> <span class="class"><span class="keyword">class</span> <span class="title">Sum</span></span>(<span class="keyword">val</span> left: Expr, <span class="keyword">val</span> right: Expr) : Expr()</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="function"><span class="keyword">fun</span> <span class="title">eval</span><span class="params">(e: <span class="type">Expr</span>)</span></span>: <span class="built_in">Int</span> = </span><br><span class="line"> <span class="keyword">when</span>(e) {</span><br><span class="line"> <span class="keyword">is</span> Num -> e.value</span><br><span class="line"> <span class="keyword">is</span> Sum -> eval(e.left) + eval(e.right)</span><br><span class="line"> }</span><br></pre></td></tr></tbody></table></figure><p>加入<code>sealed</code>关键字后你就不需要再加上<code>else</code>分支处理其它情况了，<code>sealed</code>修饰符隐含的这个类是一个<code>open</code>类，不需要显示的添加<code>open</code>修饰符。</p><h4 id="声明一个带非默认构造方法或属性的类"><a href="#声明一个带非默认构造方法或属性的类" class="headerlink" title="声明一个带非默认构造方法或属性的类"></a>声明一个带非默认构造方法或属性的类</h4><p>一个简单的类的声明</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">User</span></span>(<span class="keyword">val</span> nickname: String)</span><br></pre></td></tr></tbody></table></figure><p>类所有的声明都在括号内，这段被括号围起来的语句块也叫做主构造方法，我们也可以自己显式的去声明一个构造方法。</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">User</span> <span class="keyword">constructor</span></span>(_nickname: String) {</span><br><span class="line"> <span class="keyword">val</span> nickname: String</span><br><span class="line"> </span><br><span class="line"> <span class="keyword">init</span> {</span><br><span class="line"> nickname = _nickname</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><code>constructor</code>用来声明构造方法，<code>init</code>是用来引入一个初始化语句块，这种语句块在类被创建的时候就会执行，可以与主构造方法一起使用，下面声明一个私有的构造方法。</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Person</span> <span class="keyword">private</span> <span class="keyword">constructor</span></span>() {}</span><br></pre></td></tr></tbody></table></figure><p>一个类也可以有多个构造方法，像<code>Java</code>一样。</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">open</span> <span class="class"><span class="keyword">class</span> <span class="title">View</span> </span>{</span><br><span class="line"> <span class="keyword">constructor</span>(context: Context) {}</span><br><span class="line"> <span class="keyword">constructor</span>(context: Context, attr: Attributeset) {}</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>调用父类的构造方法</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">MyView</span> : <span class="type">View {</span></span></span><br><span class="line"> <span class="keyword">constructor</span>(context: Context) : <span class="keyword">super</span>(context) {}</span><br><span class="line"> <span class="keyword">constructor</span>(context: Context, attr: Attributeset) : <span class="keyword">super</span>(context, attr) {}</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>也可以使用<code>this</code>关键字调用本类中的构造方法。</p><h4 id="通过getter、setter访问支持的字段"><a href="#通过getter、setter访问支持的字段" class="headerlink" title="通过getter、setter访问支持的字段"></a>通过<code>getter</code>、<code>setter</code>访问支持的字段</h4><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">User</span> <span class="keyword">constructor</span></span>(_nickname: String) {</span><br><span class="line"> <span class="keyword">val</span> nickname: String = _nickname</span><br><span class="line"> <span class="keyword">var</span> sex: String = <span class="string">""</span></span><br><span class="line"> <span class="keyword">set</span>(value) {</span><br><span class="line"> field = <span class="string">"<span class="variable">$value</span>.com"</span></span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">get</span>() = <span class="string">"@<span class="variable">$field</span>"</span></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>关键字<code>field</code>用来访问支持的字段的值</p><h4 id="数据类"><a href="#数据类" class="headerlink" title="数据类"></a>数据类</h4><p><code>Kotlin</code>中的数据类会帮忙自动生成通用的方法，例如<code>setter</code>、<code>getter</code>等。数据类的属性推荐使用只读属性<code>val</code>，如果需要更改对象数据，也提供了一个允许<code>copy</code>类的实例方法，在<code>copy</code>的同时修改某些属性的值。</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">data</span> <span class="class"><span class="keyword">class</span> <span class="title">Person</span></span>(<span class="keyword">val</span> name: String)</span><br></pre></td></tr></tbody></table></figure><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">val</span> pp = Person(<span class="string">"张三"</span>)</span><br><span class="line"><span class="keyword">val</span> pp2 = pp.copy(name = <span class="string">"李四"</span>)</span><br><span class="line">showToast(pp2.name)</span><br><span class="line"><span class="comment">// 弹框输出：李四</span></span><br></pre></td></tr></tbody></table></figure><h4 id="类的委托"><a href="#类的委托" class="headerlink" title="类的委托"></a>类的委托</h4><p>通过关键字<code>by</code>实现</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="class"><span class="keyword">interface</span> <span class="title">Base</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">fun</span> <span class="title">showTag</span><span class="params">(tag: <span class="type">String</span>)</span></span></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">BaseImpl</span> : <span class="type">Base {</span></span></span><br><span class="line"> <span class="keyword">override</span> <span class="function"><span class="keyword">fun</span> <span class="title">showTag</span><span class="params">(tag: <span class="type">String</span>)</span></span> {</span><br><span class="line"> println(tag)</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">DriverBaseImpl</span></span>(<span class="keyword">private</span> <span class="keyword">val</span> base: BaseImpl) : Base <span class="keyword">by</span> base</span><br></pre></td></tr></tbody></table></figure><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line">DriverBaseImpl(BaseImpl()).showTag(<span class="string">"tag"</span>)</span><br></pre></td></tr></tbody></table></figure><h4 id="object关键字"><a href="#object关键字" class="headerlink" title="object关键字"></a><code>object</code>关键字</h4><p><code>Kotlin</code>中<code>object</code>关键字在多种情况下会出现，这个关键字定义一个类并同时创建一个实例：</p><ul><li>对象声明是定义单例的一种方式。</li><li>伴生对象可以持有工厂方法和其它与这个类先关，但在调用时并不依赖类实例的方法，它们的成员可以通过类名来访问，</li><li>对象表达式用来替代<code>Java</code>的匿名内部类。</li></ul><h5 id="对象声明，创建单例"><a href="#对象声明，创建单例" class="headerlink" title="对象声明，创建单例"></a>对象声明，创建单例</h5><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">object</span> PayType {</span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">val</span> allType = arrayListOf(<span class="string">"支付宝"</span>, <span class="string">"微信"</span>, <span class="string">"银联"</span>)</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">fun</span> <span class="title">printAllPayType</span><span class="params">()</span></span> {</span><br><span class="line"> <span class="keyword">for</span> (payType <span class="keyword">in</span> allType) {</span><br><span class="line"> println(payType)</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line">PayType.printAllPayType()</span><br></pre></td></tr></tbody></table></figure><p>与类一样，一个对象声明可以包含属性、方法、初始化语句块等的声明，唯一不允许的是构造方法，与普通类实例不一样的是对象声明在定义的时候就立即创建了，不需要再代码的其它地方调用构造方法之类的。</p><script> document.querySelectorAll('.github-emoji') .forEach(el => { if (!el.dataset.src) { return; } const img = document.createElement('img'); img.style = 'display:none !important;'; img.src = el.dataset.src; img.addEventListener('error', () => { img.remove(); el.style.color = 'inherit'; el.style.backgroundImage = 'none'; el.style.background = 'none'; }); img.addEventListener('load', () => { img.remove(); }); document.body.appendChild(img); }); </script>]]></content>
<summary type="html">
<h3 id="函数声明"><a href="#函数声明" class="headerlink" title="函数声明"></a>函数声明</h3><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="function"><span class="keyword">fun</span> <span class="title">max</span><span class="params">(a: <span class="type">Int</span>, b: <span class="type">Int</span>)</span></span>: <span class="built_in">Int</span> = <span class="keyword">if</span>(a&gt;b) a <span class="keyword">else</span> b</span><br></pre></td></tr></tbody></table></figure>
<p>关键字<code>fun</code>，名称<code>max</code>，括号内的参数列表，先参数名，冒号后面是参数类型，括号后面的冒号跟着返回值类型，如果没有返回值就把冒号跟返回值类型直接去掉，<code>kotlin</code>里面<code>if</code>是有结果的表达式。</p>
<h3 id="变量声明"><a href="#变量声明" class="headerlink" title="变量声明"></a>变量声明</h3><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">val</span> a = <span class="number">1</span></span><br><span class="line"><span class="keyword">val</span> a: <span class="built_in">Int</span> = <span class="number">1</span></span><br><span class="line"><span class="keyword">var</span> b = <span class="number">2</span></span><br><span class="line"><span class="keyword">var</span> b: <span class="built_in">Int</span> = <span class="number">2</span></span><br></pre></td></tr></tbody></table></figure>
<p>声明变量的关键字有两个不可变引用<code>val</code>、可变引用<code>var</code>，默认情况下尽可能用<code>val</code>去声明变量，仅在必要的时候把变量声明为<code>var</code>，这样可以让你的代码更接近函数式编程风格。声明变量的时候可以显式的指定变量的类型，也可以直接隐藏去掉(如果已经可以推断出类型)</p>
<h3 id="字符串格式化模板"><a href="#字符串格式化模板" class="headerlink" title="字符串格式化模板"></a>字符串格式化模板</h3><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">val</span> name = <span class="string">"bob"</span></span><br><span class="line"><span class="keyword">val</span> sex = <span class="string">"男"</span></span><br><span class="line"><span class="keyword">val</span> age = <span class="number">100</span></span><br><span class="line">print(<span class="string">"<span class="subst">${name}</span>的性别为：<span class="variable">$sex</span>，年龄为：<span class="variable">$age</span>"</span>)</span><br><span class="line"></span><br><span class="line"><span class="comment">// 输出结果：bob的性别为：男，年龄为：100</span></span><br></pre></td></tr></tbody></table></figure>
<p>可以直接用<code>$</code>符号对变量进行引用，还可以用<code>${}</code>这种对表达式进行引用，就像刚才的例子那样，<code>name</code>可以换成表达式进行使用。</p>
</summary>
<category term="Android" scheme="https://keee.top/categories/Android/"/>
<category term="kotlin" scheme="https://keee.top/tags/kotlin/"/>
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<entry>
<title>Kotlin常见作用域函数</title>
<link href="https://keee.top/2020/052242399.html"/>
<id>https://keee.top/2020/052242399.html</id>
<published>2020-05-22T10:05:53.000Z</published>
<updated>2020-05-22T10:05:53.000Z</updated>
<content type="html"><![CDATA[<ul><li>let函数</li></ul><blockquote><p>定义一个变量在一个特定的作用域内，避免写一些判空操作</p></blockquote><h5 id="使用："><a href="#使用：" class="headerlink" title="使用："></a>使用：</h5><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line">非空变量，使用it代替<span class="keyword">object</span>对象去访问其公有属性：</span><br><span class="line"><span class="keyword">object</span>.let {</span><br><span class="line">it.xxx()</span><br><span class="line"><span class="comment">// 999</span></span><br><span class="line"> <span class="comment">// return 888</span></span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">可空变量，判空操作，函数内it不为空：</span><br><span class="line"><span class="keyword">object</span>?.let {</span><br><span class="line">it.xxx()</span><br><span class="line"><span class="comment">// 999</span></span><br><span class="line"> <span class="comment">// return 888</span></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>返回值：最后一行 return 的表达式</p><a id="more"></a><ul><li>with函数</li></ul><blockquote><p>调用一个对象的多个方法 or 属性时，可以省去对象名的重复，直接调用方法 or 属性即可</p></blockquote><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line">with(<span class="keyword">object</span>) {</span><br><span class="line"> <span class="comment">// object本身的一些方法或属性，不需要再object.xxx</span></span><br><span class="line"><span class="comment">// 999</span></span><br><span class="line"> <span class="comment">// return 888</span></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>返回值：最后一行 return 的表达式</p><ul><li>apply函数</li></ul><blockquote><p>结合了 <code>let</code>、<code>with</code> 两个函数的作用，适合链式调用</p></blockquote><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">object</span>.apply {</span><br><span class="line"> <span class="comment">// 返回值是object本身</span></span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="keyword">object</span>?.apply {</span><br><span class="line"> <span class="comment">// 返回值是object本身</span></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>返回值：返回调用者本身</p><ul><li>run函数</li></ul><blockquote><p>作用类似与 <code>apply</code> 函数，两者区别于返回值</p></blockquote><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">object</span>.run {</span><br><span class="line"> <span class="comment">// 999</span></span><br><span class="line"> <span class="comment">// return 888</span></span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="keyword">object</span>?.run {</span><br><span class="line"> <span class="comment">// 999</span></span><br><span class="line"> <span class="comment">// return 888</span></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>返回值：返回最后一行 return 的表达式</p><ul><li>also函数</li></ul><blockquote><p>类似与 <code>let</code> 函数，区别在于返回值</p></blockquote><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">object</span>.also {</span><br><span class="line"> <span class="comment">// 返回值是object本身</span></span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="keyword">object</span>?.also {</span><br><span class="line"> <span class="comment">// 返回值是object本身</span></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>返回值：返回调用者本身</p><h4 id="总结："><a href="#总结：" class="headerlink" title="总结："></a>总结：</h4><ol><li>返回本身的函数有 <code>also</code>、<code>apply</code>，其它的 <code>let</code>、<code>with</code>、<code>run</code> 返回的都是末行或者 <code>return</code> 表达式。</li><li>除了 <code>with</code> 方法没有判空作用，其它均可以进行判空处理。</li></ol><script> document.querySelectorAll('.github-emoji') .forEach(el => { if (!el.dataset.src) { return; } const img = document.createElement('img'); img.style = 'display:none !important;'; img.src = el.dataset.src; img.addEventListener('error', () => { img.remove(); el.style.color = 'inherit'; el.style.backgroundImage = 'none'; el.style.background = 'none'; }); img.addEventListener('load', () => { img.remove(); }); document.body.appendChild(img); }); </script>]]></content>
<summary type="html">
<ul>
<li>let函数</li>
</ul>
<blockquote>
<p>定义一个变量在一个特定的作用域内，避免写一些判空操作</p>
</blockquote>
<h5 id="使用："><a href="#使用：" class="headerlink" title="使用："></a>使用：</h5><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line">非空变量，使用it代替<span class="keyword">object</span>对象去访问其公有属性：</span><br><span class="line"><span class="keyword">object</span>.let {</span><br><span class="line"> it.xxx()</span><br><span class="line"> <span class="comment">// 999</span></span><br><span class="line"> <span class="comment">// return 888</span></span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">可空变量，判空操作，函数内it不为空：</span><br><span class="line"><span class="keyword">object</span>?.let {</span><br><span class="line"> it.xxx()</span><br><span class="line"> <span class="comment">// 999</span></span><br><span class="line"> <span class="comment">// return 888</span></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure>
<p>返回值：最后一行 return 的表达式</p>
</summary>
<category term="Android" scheme="https://keee.top/categories/Android/"/>
<category term="kotlin" scheme="https://keee.top/tags/kotlin/"/>
</entry>
<entry>
<title>Synchronize & ReentrantLock</title>
<link href="https://keee.top/2020/052261209.html"/>
<id>https://keee.top/2020/052261209.html</id>
<published>2020-05-22T10:05:53.000Z</published>
<updated>2020-05-22T10:05:53.000Z</updated>
<content type="html"><![CDATA[<h5 id="synchronized"><a href="#synchronized" class="headerlink" title="synchronized"></a>synchronized</h5><p><code>synchronized</code> 可以用来修饰以下 3 个层面：</p><ol><li><p>修饰实例方法</p><figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">int</span> count = <span class="number">0</span>;</span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">synchronized</span> <span class="keyword">void</span> <span class="title">log</span><span class="params">(String text)</span> </span>{</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> index = <span class="number">0</span>; index < <span class="number">5</span>; index++) {</span><br><span class="line"> count++;</span><br><span class="line"> System.out.println(Thread.currentThread().getName() + <span class="string">"："</span> + text + <span class="string">"："</span> + count);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>这种情况下的锁对象是 <code>当前实例对象</code> ，因此只有同一个实例对象调用此方法才会产生互斥效果，不同实例对象之间不会有互斥效果。</p><figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> static void main(String[] args) {</span><br><span class="line"> LockTest t1 = new LockTest();</span><br><span class="line"> LockTest t2 = new LockTest();</span><br><span class="line"> Thread thread1 = new Thread(() -> t1.log(<span class="string">"测试1"</span>));</span><br><span class="line"> Thread thread2 = new Thread(() -> t2.log(<span class="string">"测试2"</span>));</span><br><span class="line"> thread1.start();</span><br><span class="line"> thread2.start();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>上面代码例子，调用的是不通对象的实例方法，所以彼此之间是不会有排斥的，运行输出如下：</p><p><img src="https://s1.ax1x.com/2020/05/18/YfXwYF.png" alt="YfXwYF.png"></p></li><li><p>修饰静态方法</p><figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">int</span> index = <span class="number">0</span>;</span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">synchronized</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">print</span><span class="params">(String text)</span> </span>{</span><br><span class="line"> index++;</span><br><span class="line"> System.out.println(Thread.currentThread().getName() + <span class="string">"："</span> + text + <span class="string">"："</span> + index);</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><a id="more"></a></li><li><p>修饰代码块</p><figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">int</span> count = <span class="number">0</span>;</span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">println</span><span class="params">(String text)</span> </span>{</span><br><span class="line"> <span class="keyword">synchronized</span> (<span class="keyword">this</span>) {</span><br><span class="line"> count++;</span><br><span class="line"> System.out.println(Thread.currentThread().getName() + <span class="string">"："</span> + text + <span class="string">"："</span> + count);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>或者</p><figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">int</span> count = <span class="number">0</span>;</span><br><span class="line"><span class="keyword">private</span> <span class="keyword">final</span> Object lock = <span class="keyword">new</span> Object();</span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">println</span><span class="params">(String text)</span> </span>{</span><br><span class="line"> <span class="keyword">synchronized</span> (lock) {</span><br><span class="line"> count++;</span><br><span class="line"> System.out.println(Thread.currentThread().getName() + <span class="string">"："</span> + text + <span class="string">"："</span> + count);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure></li></ol><h5 id="ReentrantLock"><a href="#ReentrantLock" class="headerlink" title="ReentrantLock"></a>ReentrantLock</h5><p><code>ReentrantLock</code> 的使用同 <code>synchronized</code> 有点不同，它的加锁和解锁操作都需要<code>手动完成</code>：</p><figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">int</span> count = <span class="number">0</span>;</span><br><span class="line"><span class="keyword">private</span> ReentrantLock reentrantLock = <span class="keyword">new</span> ReentrantLock();</span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">print</span><span class="params">(String text)</span> </span>{</span><br><span class="line"> reentrantLock.lock();</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> System.out.println(Thread.currentThread().getName() + <span class="string">"："</span> + text + <span class="string">"："</span> + count);</span><br><span class="line"> } <span class="keyword">catch</span> (Exception e) {</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> reentrantLock.unlock();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p> <code>lock()</code> 和 <code>unlock()</code> 分别是加锁和解锁操作。<code>ReentrantLock</code> 与 <code>synchronized</code> 不同，当异常发生时 <code>synchronized</code> 会自动释放锁，但是 <code>ReentrantLock</code> 并不会自动释放锁。因此好的方式是将 <code>unlock</code> 操作放在 <code>finally</code> 代码块中，保证任何时候锁都能够被正常释放掉。</p><p>默认情况下，<code>synchronized</code> 和 <code>ReentrantLock</code> 都是<code>非公平锁</code>。但是 <code>ReentrantLock</code> 可以通过传入 <code>true</code> 来创建一个公平锁。所谓公平锁就是通过同步队列来实现多个线程按照<code>申请锁的顺序</code>获取锁。</p><figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment">* Creates an instance of {<span class="doctag">@code</span> ReentrantLock} with the</span></span><br><span class="line"><span class="comment">* given fairness policy.</span></span><br><span class="line"><span class="comment">*</span></span><br><span class="line"><span class="comment">* <span class="doctag">@param</span> fair {<span class="doctag">@code</span> true} if this lock should use a fair ordering policy</span></span><br><span class="line"><span class="comment">*/</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="title">ReentrantLock</span><span class="params">(<span class="keyword">boolean</span> fair)</span> </span>{</span><br><span class="line"> sync = fair ? <span class="keyword">new</span> FairSync() : <span class="keyword">new</span> NonfairSync();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>创建一个公平锁：</p><figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">int</span> count = <span class="number">0</span>;</span><br><span class="line"><span class="keyword">private</span> ReentrantLock reentrantLock = <span class="keyword">new</span> ReentrantLock(<span class="keyword">true</span>);</span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">print</span><span class="params">(String text)</span> </span>{</span><br><span class="line"> reentrantLock.lock();</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> System.out.println(Thread.currentThread().getName() + <span class="string">"："</span> + text + <span class="string">"："</span> + count);</span><br><span class="line"> } <span class="keyword">catch</span> (Exception e) {</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> reentrantLock.unlock();</span><br><span class="line">}</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><h5 id="读写锁（ReentrantReadWriteLock）"><a href="#读写锁（ReentrantReadWriteLock）" class="headerlink" title="读写锁（ReentrantReadWriteLock）"></a>读写锁（ReentrantReadWriteLock）</h5><p>创建读写锁：</p><figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> ReentrantReadWriteLock reentrantReadWriteLock = <span class="keyword">new</span> ReentrantReadWriteLock();</span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">test</span><span class="params">()</span> </span>{</span><br><span class="line"> <span class="comment">// 读操作</span></span><br><span class="line"> reentrantReadWriteLock.readLock().lock();</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> } <span class="keyword">catch</span> (Exception e) {</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> reentrantReadWriteLock.readLock().unlock();</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">// 写操作</span></span><br><span class="line"> reentrantReadWriteLock.writeLock().lock();</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> } <span class="keyword">catch</span> (Exception e) {</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> reentrantReadWriteLock.writeLock().unlock();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><script> document.querySelectorAll('.github-emoji') .forEach(el => { if (!el.dataset.src) { return; } const img = document.createElement('img'); img.style = 'display:none !important;'; img.src = el.dataset.src; img.addEventListener('error', () => { img.remove(); el.style.color = 'inherit'; el.style.backgroundImage = 'none'; el.style.background = 'none'; }); img.addEventListener('load', () => { img.remove(); }); document.body.appendChild(img); }); </script>]]></content>
<summary type="html">
<h5 id="synchronized"><a href="#synchronized" class="headerlink" title="synchronized"></a>synchronized</h5><p><code>synchronized</code> 可以用来修饰以下 3 个层面：</p>
<ol>
<li><p>修饰实例方法</p>
<figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">int</span> count = <span class="number">0</span>;</span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">synchronized</span> <span class="keyword">void</span> <span class="title">log</span><span class="params">(String text)</span> </span>{</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> index = <span class="number">0</span>; index &lt; <span class="number">5</span>; index++) {</span><br><span class="line"> count++;</span><br><span class="line"> System.out.println(Thread.currentThread().getName() + <span class="string">"："</span> + text + <span class="string">"："</span> + count);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure>
<p>这种情况下的锁对象是 <code>当前实例对象</code> ，因此只有同一个实例对象调用此方法才会产生互斥效果，不同实例对象之间不会有互斥效果。</p>
<figure class="highlight kotlin"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> static void main(String[] args) {</span><br><span class="line"> LockTest t1 = new LockTest();</span><br><span class="line"> LockTest t2 = new LockTest();</span><br><span class="line"> Thread thread1 = new Thread(() -&gt; t1.log(<span class="string">"测试1"</span>));</span><br><span class="line"> Thread thread2 = new Thread(() -&gt; t2.log(<span class="string">"测试2"</span>));</span><br><span class="line"> thread1.start();</span><br><span class="line"> thread2.start();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure>
<p>上面代码例子，调用的是不通对象的实例方法，所以彼此之间是不会有排斥的，运行输出如下：</p>
<p><img src="https://s1.ax1x.com/2020/05/18/YfXwYF.png" alt="YfXwYF.png"></p>
</li>
<li><p>修饰静态方法</p>
<figure class="highlight java"><table><tbody><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">int</span> index = <span class="number">0</span>;</span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">synchronized</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">print</span><span class="params">(String text)</span> </span>{</span><br><span class="line"> index++;</span><br><span class="line"> System.out.println(Thread.currentThread().getName() + <span class="string">"："</span> + text + <span class="string">"："</span> + index);</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure></li></ol>
</summary>
<category term="Java" scheme="https://keee.top/categories/Java/"/>
<category term="多线程" scheme="https://keee.top/tags/%E5%A4%9A%E7%BA%BF%E7%A8%8B/"/>
</entry>
</feed>