Check for presence of project-wide gradle configuration properties

[christocracy]

As recommended by the Android Developer Document Gradle Tips & Tricks (See "Configure project-wide properties"), if the hosting application defines the following properties in their root build.gradle, peer modules (like react-native-maps) can align its dependencies as requested:

📂 android/build.gradle

buildscript {...}

allprojects {...}

/**
 * Project-wide gradle configuration properties for use by all modules
 */
+ext {
+    compileSdkVersion   = 26
+    targetSdkVersion    = 26
+    buildToolsVersion   = "26.0.2"
+    supportLibVersion   = "26.1.0"
+    googlePlayServicesVersion = "11.8.0"
+    androidMapsUtilsVersion = "0.5+"
+}

📂 android/app/build.gradle

android {
+    compileSdkVersion rootProject.compileSdkVersion
+    buildToolsVersion rootProject.buildToolsVersion

    defaultConfig {
+        targetSdkVersion rootProject.targetSdkVersion
    }
}
dependencies {
     compile fileTree(dir: "libs", include: ["*.jar"])
+    compile "com.android.support:appcompat-v7:$rootProject.supportLibVersion"
     compile "com.facebook.react:react-native:+"  // From node_modules

     compile project(':react-native-background-geolocation')
     compile project(':react-native-background-fetch')
     compile project(':react-native-device-info')
     compile project(':react-native-maps')
}

This provides a much better mechanism for aligning play-services version than all the nasty business of exclude group:

   ...
   dependencies {
       ...
       compile(project(':react-native-maps')){
           exclude group: 'com.google.android.gms', module: 'play-services-base'
           exclude group: 'com.google.android.gms', module: 'play-services-maps'
       }
       compile 'com.google.android.gms:play-services-base:10.0.1'
       compile 'com.google.android.gms:play-services-maps:10.0.1'
   }

Many other modules are beginning to implement this project-wide configuration properties mechansism, eg:

• react-native-background-geolocation
• react-native-background-fetch
• react-native-device-info
• react-native-firebase

[rborn]

LGTM
@christopherdro could you have a look at this please 🐽?

@christocracy thanks for the PR ❤️

[alvelig]

Oh, I get it! Yes that's a great thing

[christocracy]

Seems this was a timely addition with the big play-services 12.0.0 blow-up today ;)