Enable Flipper on RNTester app (Android)

Reviewed By: rickhanlonii

Differential Revision: D17151766

fbshipit-source-id: b71255702aaa9e102118dff3c00aae2ee654ec1a

RNTester/android/app/build.gradle

@@ -169,6 +169,12 @@ dependencies {
     debugImplementation files(hermesPath + "hermes-debug.aar")
     releaseImplementation files(hermesPath + "hermes-release.aar")
 
+    debugImplementation("com.facebook.flipper:flipper:0.23.4") {
+        exclude group:'com.facebook.yoga'
+        exclude group:'com.facebook.flipper', module: 'fbjni'
+        exclude group:'com.facebook.litho', module: 'litho-annotations'
+    }
+
     if (useIntlJsc) {
         implementation 'org.webkit:android-jsc-intl:+'
     } else {

RNTester/android/app/src/main/java/com/facebook/react/uiapp/RNTesterApplication.java

@@ -7,6 +7,7 @@
 package com.facebook.react.uiapp;
 
 import android.app.Application;
+import android.content.Context;
 import com.facebook.react.BuildConfig;
 import com.facebook.react.ReactApplication;
 import com.facebook.react.ReactNativeHost;
@@ -14,6 +15,7 @@ import com.facebook.react.ReactPackage;
 import com.facebook.react.shell.MainReactPackage;
 import com.facebook.react.views.text.ReactFontManager;
 import com.facebook.soloader.SoLoader;
+import java.lang.reflect.InvocationTargetException;
 import java.util.Arrays;
 import java.util.List;
 
@@ -46,10 +48,32 @@ public class RNTesterApplication extends Application implements ReactApplication
     ReactFontManager.getInstance().addCustomFont(this, "Rubik", R.font.rubik);
     super.onCreate();
     SoLoader.init(this, /* native exopackage */ false);
+    initializeFlipper(this);
   }
 
   @Override
   public ReactNativeHost getReactNativeHost() {
     return mReactNativeHost;
   }
+
+  private static void initializeFlipper(Context context) {
+    if (BuildConfig.DEBUG) {
+      try {
+        /*
+         We use reflection here to pick up the class that initializes Flipper,
+        since Flipper library is not available in release mode
+        */
+        Class<?> aClass = Class.forName("com.facebook.flipper.ReactNativeFlipper");
+        aClass.getMethod("initializeFlipper", Context.class).invoke(null, context);
+      } catch (ClassNotFoundException e) {
+        e.printStackTrace();
+      } catch (NoSuchMethodException e) {
+        e.printStackTrace();
+      } catch (IllegalAccessException e) {
+        e.printStackTrace();
+      } catch (InvocationTargetException e) {
+        e.printStackTrace();
+      }
+    }
+  }
 };