Upgrade to RN 56 and gradle 3

android/build.gradle

@@ -3,9 +3,10 @@
 buildscript {
     repositories {
         jcenter()
+        google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:2.2.3'
+        classpath 'com.android.tools.build:gradle:3.1.0'
 
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files
@@ -20,5 +21,17 @@ allprojects {
             // All of React Native (JS, Obj-C sources, Android binaries) is installed from npm
             url "$rootDir/../node_modules/react-native/android"
         }
+        maven {
+            url 'https://maven.google.com/'
+            name 'Google'
+        }
     }
 }
+
+ext {
+    buildToolsVersion = "26.0.3"
+    minSdkVersion = 16
+    compileSdkVersion = 26
+    targetSdkVersion = 26
+    supportLibVersion = "26.1.0"
+}