Update build.gradle

android/build.gradle

@@ -1,12 +1,17 @@
+
+def safeExtGet(prop, fallback) {
+    rootProject.ext.has(prop) ? rootProject.ext.get(prop) : fallback
+}
+
 apply plugin: 'com.android.library'
 
 android {
-    compileSdkVersion 26
-    buildToolsVersion "26.0.2"
+    compileSdkVersion safeExtGet('compileSdkVersion', 28)
+    buildToolsVersion safeExtGet('buildToolsVersion', '28.0.3')
 
     defaultConfig {
-        minSdkVersion 16
-        targetSdkVersion 25
+        minSdkVersion safeExtGet('minSdkVersion', 16)
+        targetSdkVersion safeExtGet('targetSdkVersion', 27)
         versionCode 1
         versionName "1.0"
     }
@@ -26,5 +31,5 @@ repositories {
 }
 
 dependencies {
-    compile 'com.facebook.react:react-native:+'
+    implementation 'com.facebook.react:react-native:+'
 }