Using SDK Version variables from root project

android/build.gradle

@@ -1,22 +1,31 @@
 buildscript {
     repositories {
         jcenter()
+        google()
     }
 
     dependencies {
-        classpath 'com.android.tools.build:gradle:1.3.0'
+        classpath 'com.android.tools.build:gradle:3.1.2'
     }
 }
 
 apply plugin: 'com.android.library'
 
+def _ext = rootProject.ext
+
+def _reactNativeVersion = _ext.has('reactNative') ? _ext.reactNative : '+'
+def _compileSdkVersion = _ext.has('compileSdkVersion') ? _ext.compileSdkVersion : 27
+def _buildToolsVersion = _ext.has('buildToolsVersion') ? _ext.buildToolsVersion : '27.0.3'
+def _minSdkVersion = _ext.has('minSdkVersion') ? _ext.minSdkVersion : 16
+def _targetSdkVersion = _ext.has('targetSdkVersion') ? _ext.targetSdkVersion : 27
+
 android {
-    compileSdkVersion 23
-    buildToolsVersion "23.0.1"
+    compileSdkVersion _compileSdkVersion
+    buildToolsVersion _buildToolsVersion
 
     defaultConfig {
-        minSdkVersion 16
-        targetSdkVersion 22
+        minSdkVersion _minSdkVersion
+        targetSdkVersion _targetSdkVersion
         versionCode 1
         versionName "1.0"
     }
@@ -30,5 +39,6 @@ repositories {
 }
 
 dependencies {
-    compile 'com.facebook.react:react-native:+' // from node_modules
-}
+    //noinspection GradleDynamicVersion
+    implementation "com.facebook.react:react-native:${_reactNativeVersion}"
+}