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Integration with Existing Apps

React Native is great when you are starting a new mobile app from scratch. However, it also works well for adding a single view or user flow to existing native applications. With a few steps, you can add new React Native based features, screens, views, etc.

The specific steps are different depending on what platform you're targeting.

Key Concepts​

The keys to integrating React Native components into your Android application are to:

  1. Set up the correct directory structure.
  2. Install the necessary NPM dependencies.
  3. Adding React Native to your Gradle configuration.
  4. Writing the TypeScript code for your first React Native screen.
  5. Integrate React Native with your Android code using a ReactActivity.
  6. Testing your integration by running the bundler and seeing your app in action.

Using the Community Template​

While you follow this guide, we suggest you to use the React Native Community Template as reference. The template contains a minimal Android app and will help you understanding how to integrate React Native into an existing Android app.

Prerequisites​

Follow the guide on setting up your development environment and using React Native without a framework to configure your development environment for building React Native apps for Android. This guide also assumes you're familiar with the basics of Android development such as creating Activities and editing the AndroidManifest.xml file.

1. Set up directory structure​

To ensure a smooth experience, create a new folder for your integrated React Native project, then move your existing Android project to the /android subfolder.

2. Install NPM dependencies​

Go to the root directory and run the following command:

curl -O https://raw.githubusercontent.com/react-native-community/template/refs/heads/0.75-stable/template/package.json

This will copy the package.json file from the Community template to your project.

Next, install the NPM packages by running:

npm install

Installation process has created a new node_modules folder. This folder stores all the JavaScript dependencies required to build your project.

Add node_modules/ to your .gitignore file (here the Community default one).

3. Adding React Native to your app​

Configuring Gradle​

React Native uses the React Native Gradle Plugin to configure your dependencies and project setup.

First, let's edit your settings.gradle file by adding those lines (as suggested from the Community template):

// Configures the React Native Gradle Settings plugin used for autolinking
pluginManagement { includeBuild("../node_modules/@react-native/gradle-plugin") }
plugins { id("com.facebook.react.settings") }
extensions.configure(com.facebook.react.ReactSettingsExtension){ ex -> ex.autolinkLibrariesFromCommand() }
// If using .gradle.kts files:
// extensions.configure<com.facebook.react.ReactSettingsExtension> { autolinkLibrariesFromCommand() }
includeBuild("../node_modules/@react-native/gradle-plugin")

// Include your existing Gradle modules here.
// include(":app")

Then you need to open your top level build.gradle and include this line (as suggested from the Community template):

buildscript {
    repositories {
        google()
        mavenCentral()
    }
    dependencies {
        classpath("com.android.tools.build:gradle:7.3.1")
+       classpath("com.facebook.react:react-native-gradle-plugin")
    }
}

This makes sure the React Native Gradle Plugin (RNGP) is available inside your project. Finally, add those lines inside your Applications's build.gradle file (it's a different build.gradle file usually inside your app folder - you can use the Community template file as reference):

apply plugin: "com.android.application"
+apply plugin: "com.facebook.react"

repositories {
    mavenCentral()
}

dependencies {
    // Other dependencies here
+   // Note: we intentionally don't specify the version number here as RNGP will take care of it.
+   // If you don't use the RNGP, you'll have to specify version manually.
+   implementation("com.facebook.react:react-android")
+   implementation("com.facebook.react:hermes-android")
}

+react {
+   // Needed to enable Autolinking - https://github.com/react-native-community/cli/blob/master/docs/autolinking.md
+   autolinkLibrariesWithApp()
+}

Finally, open your application gradle.properties files and add the following line (here the Community template file as reference):

+reactNativeArchitectures=armeabi-v7a,arm64-v8a,x86,x86_64
+newArchEnabled=true
+hermesEnabled=true

Configuring your manifest​

First, make sure you have the Internet permission in your AndroidManifest.xml:

<manifest xmlns:android="http://schemas.android.com/apk/res/android">

+   <uses-permission android:name="android.permission.INTERNET" />

    <application
      android:name=".MainApplication">
    </application>
</manifest>

Then you need to enable cleartext traffic in your debug AndroidManifest.xml:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools">

    <application
+       android:usesCleartextTraffic="true"
+       tools:targetApi="28"
    />
</manifest>

As usual, here the AndroidManifest.xml file from the Community template to use as a reference: main and debug

This is needed as your application will communicate with your local bundler, [Metro][https://metrobundler.dev/], via HTTP.

Make sure you add this only to your debug manifest.

4. Writing the TypeScript Code​

Now we will actually modify the native Android application to integrate React Native.

The first bit of code we will write is the actual React Native code for the new screen that will be integrated into our application.

Create a index.js file​

First, create an empty index.js file in the root of your React Native project.

index.js is the starting point for React Native applications, and it is always required. It can be a small file that imports other file that are part of your React Native component or application, or it can contain all the code that is needed for it.

Our index.js should look as follows (here the Community template file as reference):

import {AppRegistry} from 'react-native';
import App from './App';

AppRegistry.registerComponent('HelloWorld', () => App);

Create a App.tsx file​

Let's create an App.tsx file. This is a TypeScript file that can have JSX expressions. It contains the root React Native component that we will integrate into our Android application (link):

import React from 'react';
import {
  SafeAreaView,
  ScrollView,
  StatusBar,
  StyleSheet,
  Text,
  useColorScheme,
  View,
} from 'react-native';

import {
  Colors,
  DebugInstructions,
  Header,
  ReloadInstructions,
} from 'react-native/Libraries/NewAppScreen';

function App(): React.JSX.Element {
  const isDarkMode = useColorScheme() === 'dark';

  const backgroundStyle = {
    backgroundColor: isDarkMode ? Colors.darker : Colors.lighter,
  };

  return (
    <SafeAreaView style={backgroundStyle}>
      <StatusBar
        barStyle={isDarkMode ? 'light-content' : 'dark-content'}
        backgroundColor={backgroundStyle.backgroundColor}
      />
      <ScrollView
        contentInsetAdjustmentBehavior="automatic"
        style={backgroundStyle}>
        <Header />
        <View
          style={{
            backgroundColor: isDarkMode
              ? Colors.black
              : Colors.white,
            padding: 24,
          }}>
          <Text style={styles.title}>Step One</Text>
          <Text>
            Edit <Text style={styles.bold}>App.tsx</Text> to
            change this screen and see your edits.
          </Text>
          <Text style={styles.title}>See your changes</Text>
          <ReloadInstructions />
          <Text style={styles.title}>Debug</Text>
          <DebugInstructions />
        </View>
      </ScrollView>
    </SafeAreaView>
  );
}

const styles = StyleSheet.create({
  title: {
    fontSize: 24,
    fontWeight: '600',
  },
  bold: {
    fontWeight: '700',
  },
});

export default App;

Here the Community template file as reference

5. Integrating with your Android code​

We now need to add some native code in order to start the React Native runtime and tell it to render our React components.

Updating your Application class​

First, we need to update your Application class to properly initialize React Native as follows:

package <your-package-here>;

import android.app.Application;
+import com.facebook.react.PackageList;
+import com.facebook.react.ReactApplication;
+import com.facebook.react.ReactHost;
+import com.facebook.react.ReactNativeHost;
+import com.facebook.react.ReactPackage;
+import com.facebook.react.defaults.DefaultNewArchitectureEntryPoint;
+import com.facebook.react.defaults.DefaultReactHost;
+import com.facebook.react.defaults.DefaultReactNativeHost;
+import com.facebook.soloader.SoLoader;
+import com.facebook.react.soloader.OpenSourceMergedSoMapping
+import java.util.List;

-class MainApplication extends Application {
+class MainApplication extends Application implements ReactApplication {
+ @Override
+ public ReactNativeHost getReactNativeHost() {
+   return new DefaultReactNativeHost(this) {
+     @Override
+     protected List<ReactPackage> getPackages() { return new PackageList(this).getPackages(); }
+     @Override
+     protected String getJSMainModuleName() { return "index"; }
+     @Override
+     public boolean getUseDeveloperSupport() { return BuildConfig.DEBUG; }
+     @Override
+     protected boolean isNewArchEnabled() { return BuildConfig.IS_NEW_ARCHITECTURE_ENABLED; }
+     @Override
+     protected Boolean isHermesEnabled() { return BuildConfig.IS_HERMES_ENABLED; }
+   };
+ }

+ @Override
+ public ReactHost getReactHost() {
+   return DefaultReactHost.getDefaultReactHost(getApplicationContext(), getReactNativeHost());
+ }

  @Override
  public void onCreate() {
    super.onCreate();
+   SoLoader.init(this, OpenSourceMergedSoMapping);
+   if (BuildConfig.IS_NEW_ARCHITECTURE_ENABLED) {
+     DefaultNewArchitectureEntryPoint.load();
+   }
  }
}

As usual, here the MainApplication.kt Community template file as reference

Creating a ReactActivity​

Finally, we need to create a new Activity that will extend ReactActivity and host the React Native code. This activity will be responsible for starting the React Native runtime and rendering the React component.

// package <your-package-here>;

import com.facebook.react.ReactActivity;
import com.facebook.react.ReactActivityDelegate;
import com.facebook.react.defaults.DefaultNewArchitectureEntryPoint;
import com.facebook.react.defaults.DefaultReactActivityDelegate;

public class MyReactActivity extends ReactActivity {

    @Override
    protected String getMainComponentName() {
        return "HelloWorld";
    }

    @Override
    protected ReactActivityDelegate createReactActivityDelegate() {
        return new DefaultReactActivityDelegate(this, getMainComponentName(), DefaultNewArchitectureEntryPoint.getFabricEnabled());
    }
}

As usual, here the MainActivity.kt Community template file as reference

Whenever you create a new Activity, you need to add it to your AndroidManifest.xml file. You also need set the theme of MyReactActivity to Theme.AppCompat.Light.NoActionBar (or to any non-ActionBar theme) as otherwise your application will render an ActionBar on top of your React Native screen:

<manifest xmlns:android="http://schemas.android.com/apk/res/android">

    <uses-permission android:name="android.permission.INTERNET" />

    <application
      android:name=".MainApplication">

+     <activity
+       android:name=".MyReactActivity"
+       android:label="@string/app_name"
+       android:theme="@style/Theme.AppCompat.Light.NoActionBar">
+     </activity>
    </application>
</manifest>

Now your activity is ready to run some JavaScript code.

6. Test your integration​

You have completed all the basic steps to integrate React Native with your application. Now we will start the Metro bundler to build your TypeScript application code into a bundle. Metro's HTTP server shares the bundle from localhost on your developer environment to a simulator or device. This allows for hot reloading.

First, you need to create a metro.config.js file in the root of your project as follows:

const {getDefaultConfig} = require('@react-native/metro-config');
module.exports = getDefaultConfig(__dirname);

You can checkout the metro.config.js file from the Community template file as reference.

Once you have the config file in place, you can run the bundler. Run the following command in the root directory of your project:

npm start

Now build and run your Android app as normal.

Once you reach your React-powered Activity inside the app, it should load the JavaScript code from the development server and display:

Creating a release build in Android Studio​

You can use Android Studio to create your release builds too! It’s as quick as creating release builds of your previously-existing native Android app.

The React Native Gradle Plugin will take care of bundling the JS code inside your APK/App Bundle.

If you're not using Android Studio, you can create a release build with:

cd android
# For a Release APK
./gradlew :app:assembleRelease
# For a Release AAB
./gradlew :app:bundleRelease

Now what?​

At this point you can continue developing your app as usual. Refer to our debugging and deployment docs to learn more about working with React Native.