fixed Gradle setup (#131)

Author: SaeedZhiany

android/build.gradle

@@ -1,30 +1,31 @@
 buildscript {
-  repositories {
-    google()
-    jcenter()
-  }
+  // The Android Gradle plugin is only required when opening the android folder stand-alone.
+  // This avoids unnecessary downloads and potential conflicts when the library is included as a
+  // module dependency in an application project.
+  if (project == rootProject) {
+    repositories {
+      google()
+      jcenter()
+    }
 
-  dependencies {
-    classpath 'com.android.tools.build:gradle:3.2.1'
+    dependencies {
+      classpath("com.android.tools.build:gradle:3.6.3")
+    }
   }
 }
 
 apply plugin: 'com.android.library'
 
-def getExtOrDefault(name) {
-  return rootProject.ext.has(name) ? rootProject.ext.get(name) : project.properties['Restart_' + name]
-}
-
-def getExtOrIntegerDefault(name) {
-  return rootProject.ext.has(name) ? rootProject.ext.get(name) : (project.properties['Restart_' + name]).toInteger()
+def safeExtGet(name) {
+  rootProject.ext.has(name) ? rootProject.ext.get(name) : project.properties[name]
 }
 
 android {
-  compileSdkVersion getExtOrIntegerDefault('compileSdkVersion')
-  buildToolsVersion getExtOrDefault('buildToolsVersion')
+  compileSdkVersion safeExtGet('compileSdkVersion')
+
   defaultConfig {
-    minSdkVersion 16
-    targetSdkVersion getExtOrIntegerDefault('targetSdkVersion')
+    minSdkVersion safeExtGet('minSdkVersion')
+    targetSdkVersion safeExtGet('targetSdkVersion')
     versionCode 1
     versionName "1.0"
   }
@@ -114,6 +115,5 @@ repositories {
 }
 
 dependencies {
-  // noinspection GradleDynamicVersion
   api 'com.facebook.react:react-native:+'
 }

android/gradle.properties

@@ -1,3 +1,3 @@
-Restart_compileSdkVersion=28
-Restart_buildToolsVersion=28.0.3
-Restart_targetSdkVersion=28
+compileSdkVersion=28
+minSdkVersion=16
+targetSdkVersion=28