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.
- Android (Kotlin)
- Android (Java)
- iOS (Objective-C)
- iOS (Swift)
Key Concepts
The keys to integrating React Native components into your Android application are to:
- Set up React Native dependencies and directory structure.
- Develop your React Native components in JavaScript.
- Add a
ReactRootView
to your Android app. This view will serve as the container for your React Native component. - Start the React Native server and run your native application.
- Verify that the React Native aspect of your application works as expected.
Prerequisites
Follow the React Native CLI Quickstart in the environment setup guide to configure your development environment for building React Native apps for Android.
1. Set up directory structure
To ensure a smooth experience, create a new folder for your integrated React Native project, then copy your existing Android project to an /android
subfolder.
2. Install JavaScript dependencies
Go to the root directory for your project and create a new package.json
file with the following contents:
{
"name": "MyReactNativeApp",
"version": "0.0.1",
"private": true,
"scripts": {
"start": "yarn react-native start"
}
}
Next, install the react
and react-native
packages. Open a terminal or command prompt, then navigate to the directory with your package.json
file and run:
- npm
- Yarn
npm install react-native
yarn add react-native
This will print a message similar to the following (scroll up in the installation command output to see it):
warning "
react-native@0.70.5
" has unmet peer dependency "react@18.1.0
"
This is OK, it means we also need to install React:
- npm
- Yarn
npm install react@version_printed_above
yarn add react@version_printed_above
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.
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 this line:
includeBuild('../node_modules/@react-native/gradle-plugin')
Then you need to open your top level build.gradle
and include this line:
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 is available inside your project.
Finally, add those lines inside your app's build.gradle
file (it's a different build.gradle
file inside your app folder):
apply plugin: "com.android.application"
+apply plugin: "com.facebook.react"
repositories {
mavenCentral()
}
dependencies {
// Other dependencies here
+ implementation "com.facebook.react:react-android"
+ implementation "com.facebook.react:hermes-android"
}
Those dependencies are available on mavenCentral()
so make sure you have it defined in your repositories{}
block.
We intentionally don't specify the version for those implementation
dependencies as the React Native Gradle Plugin will take care of it. If you don't use the React Native Gradle Plugin, you'll have to specify version manually.
Enable native modules autolinking
To use the power of autolinking, we have to apply it a few places. First add the following entry to settings.gradle
:
apply from: file("../node_modules/@react-native-community/cli-platform-android/native_modules.gradle"); applyNativeModulesSettingsGradle(settings)
Next add the following entry at the very bottom of the app/build.gradle
:
apply from: file("../../node_modules/@react-native-community/cli-platform-android/native_modules.gradle"); applyNativeModulesAppBuildGradle(project)
Configuring permissions
Next, make sure you have the Internet permission in your AndroidManifest.xml
:
<uses-permission android:name="android.permission.INTERNET" />
If you need to access to the DevSettingsActivity
add to your AndroidManifest.xml
:
<activity android:name="com.facebook.react.devsupport.DevSettingsActivity" />
This is only used in dev mode when reloading JavaScript from the development server, so you can strip this in release builds if you need to.
Cleartext Traffic (API level 28+)
Starting with Android 9 (API level 28), cleartext traffic is disabled by default; this prevents your application from connecting to the Metro bundler. The changes below allow cleartext traffic in debug builds.
1. Apply the usesCleartextTraffic
option to your Debug AndroidManifest.xml
<!-- ... -->
<application
android:usesCleartextTraffic="true" tools:targetApi="28" >
<!-- ... -->
</application>
<!-- ... -->
This is not required for Release builds.
To learn more about Network Security Config and the cleartext traffic policy see this link.
Code integration
Now we will actually modify the native Android application to integrate React Native.
The React Native component
The first bit of code we will write is the actual React Native code for the new "High Score" screen that will be integrated into our application.
1. 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 require
s other file that are part of your React Native component or application, or it can contain all the code that is needed for it. In our case, we will put everything in index.js
.
2. Add your React Native code
In your index.js
, create your component. In our sample here, we will add a <Text>
component within a styled <View>
:
import React from 'react';
import {AppRegistry, StyleSheet, Text, View} from 'react-native';
const HelloWorld = () => {
return (
<View style={styles.container}>
<Text style={styles.hello}>Hello, World</Text>
</View>
);
};
const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: 'center',
},
hello: {
fontSize: 20,
textAlign: 'center',
margin: 10,
},
});
AppRegistry.registerComponent(
'MyReactNativeApp',
() => HelloWorld,
);
3. Configure permissions for development error overlay
If your app is targeting the Android API level 23
or greater, make sure you have the permission android.permission.SYSTEM_ALERT_WINDOW
enabled for the development build. You can check this with Settings.canDrawOverlays(this)
. This is required in dev builds because React Native development errors must be displayed above all the other windows. Due to the new permissions system introduced in the API level 23 (Android M), the user needs to approve it. This can be achieved by adding the following code to your Activity's in onCreate()
method.
companion object {
const val OVERLAY_PERMISSION_REQ_CODE = 1 // Choose any value
}
...
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if(!Settings.canDrawOverlays(this)) {
val intent = Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION,
Uri.parse("package: $packageName"))
startActivityForResult(intent, OVERLAY_PERMISSION_REQ_CODE);
}
}
Finally, the onActivityResult()
method (as shown in the code below) has to be overridden to handle the permission Accepted or Denied cases for consistent UX. Also, for integrating Native Modules which use startActivityForResult
, we need to pass the result to the onActivityResult
method of our ReactInstanceManager
instance.
override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
if (requestCode == OVERLAY_PERMISSION_REQ_CODE) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if (!Settings.canDrawOverlays(this)) {
// SYSTEM_ALERT_WINDOW permission not granted
}
}
}
reactInstanceManager?.onActivityResult(this, requestCode, resultCode, data)
}
The Magic: ReactRootView
Let's add some native code in order to start the React Native runtime and tell it to render our JS component. To do this, we're going to create an Activity
that creates a ReactRootView
, starts a React application inside it and sets it as the main content view.
If you are targeting Android version <5, use the
AppCompatActivity
class from thecom.android.support:appcompat
package instead ofActivity
.
class MyReactActivity : Activity(), DefaultHardwareBackBtnHandler {
private lateinit var reactRootView: ReactRootView
private lateinit var reactInstanceManager: ReactInstanceManager
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
SoLoader.init(this, false)
reactRootView = ReactRootView(this)
val packages: List<ReactPackage> = PackageList(application).packages
// Packages that cannot be autolinked yet can be added manually here, for example:
// packages.add(MyReactNativePackage())
// Remember to include them in `settings.gradle` and `app/build.gradle` too.
reactInstanceManager = ReactInstanceManager.builder()
.setApplication(application)
.setCurrentActivity(this)
.setBundleAssetName("index.android.bundle")
.setJSMainModulePath("index")
.addPackages(packages)
.setUseDeveloperSupport(BuildConfig.DEBUG)
.setInitialLifecycleState(LifecycleState.RESUMED)
.build()
// The string here (e.g. "MyReactNativeApp") has to match
// the string in AppRegistry.registerComponent() in index.js
reactRootView?.startReactApplication(reactInstanceManager, "MyReactNativeApp", null)
setContentView(reactRootView)
}
override fun invokeDefaultOnBackPressed() {
super.onBackPressed()
}
}
If you are using a starter kit for React Native, replace the "HelloWorld" string with the one in your index.js file (it’s the first argument to the
AppRegistry.registerComponent()
method).
Perform a “Sync Project files with Gradle” operation.
If you are using Android Studio, use Alt + Enter
to add all missing imports in your MyReactActivity class. Be careful to use your package’s BuildConfig
and not the one from the facebook
package.
We need set the theme of MyReactActivity
to Theme.AppCompat.Light.NoActionBar
because some React Native UI components rely on this theme.
<activity
android:name=".MyReactActivity"
android:label="@string/app_name"
android:theme="@style/Theme.AppCompat.Light.NoActionBar">
</activity>
A
ReactInstanceManager
can be shared by multiple activities and/or fragments. You will want to make your ownReactFragment
orReactActivity
and have a singleton holder that holds aReactInstanceManager
. When you need theReactInstanceManager
(e.g., to hook up theReactInstanceManager
to the lifecycle of those Activities or Fragments) use the one provided by the singleton.
Next, we need to pass some activity lifecycle callbacks to the ReactInstanceManager
and ReactRootView
:
override fun onPause() {
super.onPause()
reactInstanceManager.onHostPause(this)
}
override fun onResume() {
super.onResume()
reactInstanceManager.onHostResume(this, this)
}
override fun onDestroy() {
super.onDestroy()
reactInstanceManager.onHostDestroy(this)
reactRootView.unmountReactApplication()
}
We also need to pass back button events to React Native:
override fun onBackPressed() {
reactInstanceManager.onBackPressed()
super.onBackPressed()
}
This allows JavaScript to control what happens when the user presses the hardware back button (e.g. to implement navigation). When JavaScript doesn't handle the back button press, your invokeDefaultOnBackPressed
method will be called. By default this finishes your Activity
.
Finally, we need to hook up the dev menu. By default, this is activated by (rage) shaking the device, but this is not very useful in emulators. So we make it show when you press the hardware menu button (use Ctrl + M if you're using Android Studio emulator):
override fun onKeyUp(keyCode: Int, event: KeyEvent?): Boolean {
if (keyCode == KeyEvent.KEYCODE_MENU && reactInstanceManager != null) {
reactInstanceManager.showDevOptionsDialog()
return true
}
return super.onKeyUp(keyCode, event)
}
Now your activity is ready to run some JavaScript code.
Test your integration
You have now done all the basic steps to integrate React Native with your current application. Now we will start the Metro bundler to build the index.bundle
package and the server running on localhost to serve it.
1. Run the packager
To run your app, you need to first start the development server. To do this, run the following command in the root directory of your React Native project:
- npm
- Yarn
npm start
yarn start
2. Run the app
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.
If you use the React Native Gradle Plugin as described above, everything should work when running app from Android Studio.
If you're not using the React Native Gradle Plugin, there’s one additional step which you’ll have to do before every release build. You need to execute the following to create a React Native bundle, which will be included with your native Android app:
$ npx react-native bundle --platform android --dev false --entry-file index.js --bundle-output android/com/your-company-name/app-package-name/src/main/assets/index.android.bundle --assets-dest android/com/your-company-name/app-package-name/src/main/res/
Don’t forget to replace the paths with correct ones and create the assets folder if it doesn’t exist.
Now, create a release build of your native app from within Android Studio as usual and you should be good to go!
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.
Key Concepts
The keys to integrating React Native components into your Android application are to:
- Set up React Native dependencies and directory structure.
- Develop your React Native components in JavaScript.
- Add a
ReactRootView
to your Android app. This view will serve as the container for your React Native component. - Start the React Native server and run your native application.
- Verify that the React Native aspect of your application works as expected.
Prerequisites
Follow the React Native CLI Quickstart in the environment setup guide to configure your development environment for building React Native apps for Android.
1. Set up directory structure
To ensure a smooth experience, create a new folder for your integrated React Native project, then copy your existing Android project to an /android
subfolder.
2. Install JavaScript dependencies
Go to the root directory for your project and create a new package.json
file with the following contents:
{
"name": "MyReactNativeApp",
"version": "0.0.1",
"private": true,
"scripts": {
"start": "react-native start"
}
}
Next, install the react
and react-native
packages. Open a terminal or command prompt, then navigate to the directory with your package.json
file and run:
- npm
- Yarn
npm install react-native
yarn add react-native
This will print a message similar to the following (scroll up in the installation command output to see it):
warning "
react-native@0.70.5
" has unmet peer dependency "react@18.1.0
"
This is OK, it means we also need to install React:
- npm
- Yarn
npm install react@version_printed_above
yarn add react@version_printed_above
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.
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 this line:
includeBuild('../node_modules/@react-native/gradle-plugin')
Then you need to open your top level build.gradle
and include this line:
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 is available inside your project.
Finally, add those lines inside your app's build.gradle
file (it's a different build.gradle
file inside your app folder):
apply plugin: "com.android.application"
+apply plugin: "com.facebook.react"
repositories {
mavenCentral()
}
dependencies {
// Other dependencies here
+ implementation "com.facebook.react:react-android"
+ implementation "com.facebook.react:hermes-android"
}
Those dependencies are available on mavenCentral()
so make sure you have it defined in your repositories{}
block.
We intentionally don't specify the version for those implementation
dependencies as the React Native Gradle Plugin will take care of it. If you don't use the React Native Gradle Plugin, you'll have to specify version manually.
Enable native modules autolinking
To use the power of autolinking, we have to apply it a few places. First add the following entry to settings.gradle
:
apply from: file("../node_modules/@react-native-community/cli-platform-android/native_modules.gradle"); applyNativeModulesSettingsGradle(settings)
Next add the following entry at the very bottom of the app/build.gradle
:
apply from: file("../../node_modules/@react-native-community/cli-platform-android/native_modules.gradle"); applyNativeModulesAppBuildGradle(project)
Configuring permissions
Next, make sure you have the Internet permission in your AndroidManifest.xml
:
<uses-permission android:name="android.permission.INTERNET" />
If you need to access to the DevSettingsActivity
add to your AndroidManifest.xml
:
<activity android:name="com.facebook.react.devsupport.DevSettingsActivity" />
This is only used in dev mode when reloading JavaScript from the development server, so you can strip this in release builds if you need to.
Cleartext Traffic (API level 28+)
Starting with Android 9 (API level 28), cleartext traffic is disabled by default; this prevents your application from connecting to the Metro bundler. The changes below allow cleartext traffic in debug builds.
1. Apply the usesCleartextTraffic
option to your Debug AndroidManifest.xml
<!-- ... -->
<application
android:usesCleartextTraffic="true" tools:targetApi="28" >
<!-- ... -->
</application>
<!-- ... -->
This is not required for Release builds.
To learn more about Network Security Config and the cleartext traffic policy see this link.
Code integration
Now we will actually modify the native Android application to integrate React Native.
The React Native component
The first bit of code we will write is the actual React Native code for the new "High Score" screen that will be integrated into our application.
1. 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 require
s other file that are part of your React Native component or application, or it can contain all the code that is needed for it. In our case, we will put everything in index.js
.
2. Add your React Native code
In your index.js
, create your component. In our sample here, we will add a <Text>
component within a styled <View>
:
import React from 'react';
import {AppRegistry, StyleSheet, Text, View} from 'react-native';
const HelloWorld = () => {
return (
<View style={styles.container}>
<Text style={styles.hello}>Hello, World</Text>
</View>
);
};
const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: 'center',
},
hello: {
fontSize: 20,
textAlign: 'center',
margin: 10,
},
});
AppRegistry.registerComponent(
'MyReactNativeApp',
() => HelloWorld,
);
3. Configure permissions for development error overlay
If your app is targeting the Android API level 23
or greater, make sure you have the permission android.permission.SYSTEM_ALERT_WINDOW
enabled for the development build. You can check this with Settings.canDrawOverlays(this);
. This is required in dev builds because React Native development errors must be displayed above all the other windows. Due to the new permissions system introduced in the API level 23 (Android M), the user needs to approve it. This can be achieved by adding the following code to your Activity's in onCreate()
method.
private final int OVERLAY_PERMISSION_REQ_CODE = 1; // Choose any value
...
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if (!Settings.canDrawOverlays(this)) {
Intent intent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION,
Uri.parse("package:" + getPackageName()));
startActivityForResult(intent, OVERLAY_PERMISSION_REQ_CODE);
}
}
Finally, the onActivityResult()
method (as shown in the code below) has to be overridden to handle the permission Accepted or Denied cases for consistent UX. Also, for integrating Native Modules which use startActivityForResult
, we need to pass the result to the onActivityResult
method of our ReactInstanceManager
instance.
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == OVERLAY_PERMISSION_REQ_CODE) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if (!Settings.canDrawOverlays(this)) {
// SYSTEM_ALERT_WINDOW permission not granted
}
}
}
mReactInstanceManager.onActivityResult( this, requestCode, resultCode, data );
}
The Magic: ReactRootView
Let's add some native code in order to start the React Native runtime and tell it to render our JS component. To do this, we're going to create an Activity
that creates a ReactRootView
, starts a React application inside it and sets it as the main content view.
If you are targeting Android version <5, use the
AppCompatActivity
class from thecom.android.support:appcompat
package instead ofActivity
.
public class MyReactActivity extends Activity implements DefaultHardwareBackBtnHandler {
private ReactRootView mReactRootView;
private ReactInstanceManager mReactInstanceManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
SoLoader.init(this, false);
mReactRootView = new ReactRootView(this);
List<ReactPackage> packages = new PackageList(getApplication()).getPackages();
// Packages that cannot be autolinked yet can be added manually here, for example:
// packages.add(new MyReactNativePackage());
// Remember to include them in `settings.gradle` and `app/build.gradle` too.
mReactInstanceManager = ReactInstanceManager.builder()
.setApplication(getApplication())
.setCurrentActivity(this)
.setBundleAssetName("index.android.bundle")
.setJSMainModulePath("index")
.addPackages(packages)
.setUseDeveloperSupport(BuildConfig.DEBUG)
.setInitialLifecycleState(LifecycleState.RESUMED)
.build();
// The string here (e.g. "MyReactNativeApp") has to match
// the string in AppRegistry.registerComponent() in index.js
mReactRootView.startReactApplication(mReactInstanceManager, "MyReactNativeApp", null);
setContentView(mReactRootView);
}
@Override
public void invokeDefaultOnBackPressed() {
super.onBackPressed();
}
}
If you are using a starter kit for React Native, replace the "HelloWorld" string with the one in your index.js file (it’s the first argument to the
AppRegistry.registerComponent()
method).
Perform a “Sync Project files with Gradle” operation.
If you are using Android Studio, use Alt + Enter
to add all missing imports in your MyReactActivity class. Be careful to use your package’s BuildConfig
and not the one from the facebook
package.
We need set the theme of MyReactActivity
to Theme.AppCompat.Light.NoActionBar
because some React Native UI components rely on this theme.
<activity
android:name=".MyReactActivity"
android:label="@string/app_name"
android:theme="@style/Theme.AppCompat.Light.NoActionBar">
</activity>
A
ReactInstanceManager
can be shared by multiple activities and/or fragments. You will want to make your ownReactFragment
orReactActivity
and have a singleton holder that holds aReactInstanceManager
. When you need theReactInstanceManager
(e.g., to hook up theReactInstanceManager
to the lifecycle of those Activities or Fragments) use the one provided by the singleton.
Next, we need to pass some activity lifecycle callbacks to the ReactInstanceManager
and ReactRootView
:
@Override
protected void onPause() {
super.onPause();
if (mReactInstanceManager != null) {
mReactInstanceManager.onHostPause(this);
}
}
@Override
protected void onResume() {
super.onResume();
if (mReactInstanceManager != null) {
mReactInstanceManager.onHostResume(this, this);
}
}
@Override
protected void onDestroy() {
super.onDestroy();
if (mReactInstanceManager != null) {
mReactInstanceManager.onHostDestroy(this);
}
if (mReactRootView != null) {
mReactRootView.unmountReactApplication();
}
}
We also need to pass back button events to React Native:
@Override
public void onBackPressed() {
if (mReactInstanceManager != null) {
mReactInstanceManager.onBackPressed();
} else {
super.onBackPressed();
}
}
This allows JavaScript to control what happens when the user presses the hardware back button (e.g. to implement navigation). When JavaScript doesn't handle the back button press, your invokeDefaultOnBackPressed
method will be called. By default this finishes your Activity
.
Finally, we need to hook up the dev menu. By default, this is activated by (rage) shaking the device, but this is not very useful in emulators. So we make it show when you press the hardware menu button (use Ctrl + M if you're using Android Studio emulator):
@Override
public boolean onKeyUp(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_MENU && mReactInstanceManager != null) {
mReactInstanceManager.showDevOptionsDialog();
return true;
}
return super.onKeyUp(keyCode, event);
}
Now your activity is ready to run some JavaScript code.
Test your integration
You have now done all the basic steps to integrate React Native with your current application. Now we will start the Metro bundler to build the index.bundle
package and the server running on localhost to serve it.
1. Run the packager
To run your app, you need to first start the development server. To do this, run the following command in the root directory of your React Native project:
- npm
- Yarn
npm start
yarn start
2. Run the app
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.
If you use the React Native Gradle Plugin as described above, everything should work when running app from Android Studio.
If you're not using the React Native Gradle Plugin, there’s one additional step which you’ll have to do before every release build. You need to execute the following to create a React Native bundle, which will be included with your native Android app:
$ npx react-native bundle --platform android --dev false --entry-file index.js --bundle-output android/com/your-company-name/app-package-name/src/main/assets/index.android.bundle --assets-dest android/com/your-company-name/app-package-name/src/main/res/
Don’t forget to replace the paths with correct ones and create the assets folder if it doesn’t exist.
Now, create a release build of your native app from within Android Studio as usual and you should be good to go!
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.
Key Concepts
The keys to integrating React Native components into your iOS application are to:
- Set up React Native dependencies and directory structure.
- Understand what React Native components you will use in your app.
- Add these components as dependencies using CocoaPods.
- Develop your React Native components in JavaScript.
- Add a
RCTRootView
to your iOS app. This view will serve as the container for your React Native component. - Start the React Native server and run your native application.
- Verify that the React Native aspect of your application works as expected.
Prerequisites
Follow the React Native CLI Quickstart in the environment setup guide to configure your development environment for building React Native apps for iOS.
1. Set up directory structure
To ensure a smooth experience, create a new folder for your integrated React Native project, then copy your existing iOS project to a /ios
subfolder.
2. Install JavaScript dependencies
Go to the root directory for your project and create a new package.json
file with the following contents:
{
"name": "MyReactNativeApp",
"version": "0.0.1",
"private": true,
"scripts": {
"start": "yarn react-native start"
}
}
Next, make sure you have installed the yarn package manager.
Install the react
and react-native
packages. Open a terminal or command prompt, then navigate to the directory with your package.json
file and run:
- npm
- Yarn
npm install react-native
yarn add react-native
This will print a message similar to the following (scroll up in the installation command output to see it):
warning "
react-native@0.52.2
" has unmet peer dependency "react@16.2.0
".
This is OK, it means we also need to install React:
- npm
- Yarn
npm install react@version_printed_above
yarn add react@version_printed_above
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.
3. Install CocoaPods
CocoaPods is a package management tool for iOS and macOS development. We use it to add the actual React Native framework code locally into your current project.
We recommend installing CocoaPods using Homebrew.
brew install cocoapods
It is technically possible not to use CocoaPods, but that would require manual library and linker additions that would overly complicate this process.
Adding React Native to your app
Assume the app for integration is a 2048 game. Here is what the main menu of the native application looks like without React Native.
Command Line Tools for Xcode
Install the Command Line Tools. Choose Settings... (or Preferences...) in the Xcode menu. Go to the Locations panel and install the tools by selecting the most recent version in the Command Line Tools dropdown.
Configuring CocoaPods dependencies
Before you integrate React Native into your application, you will want to decide what parts of the React Native framework you would like to integrate. We will use CocoaPods to specify which of these "subspecs" your app will depend on.
The list of supported subspec
s is available in /node_modules/react-native/React.podspec
. They are generally named by functionality. For example, you will generally always want the Core
subspec
. That will get you the AppRegistry
, StyleSheet
, View
and other core React Native libraries. If you want to add the React Native Text
library (e.g., for <Text>
elements), then you will need the RCTText
subspec
. If you want the Image
library (e.g., for <Image>
elements), then you will need the RCTImage
subspec
.
You can specify which subspec
s your app will depend on in a Podfile
file. The easiest way to create a Podfile
is by running the CocoaPods init
command in the /ios
subfolder of your project:
pod init
The Podfile
will contain a boilerplate setup that you will tweak for your integration purposes.
The
Podfile
version changes depending on your version ofreact-native
. Refer to https://react-native-community.github.io/upgrade-helper/ for the specific version ofPodfile
you should be using.
Ultimately, your Podfile
should look something similar to this:
# The target name is most likely the name of your project.
target 'NumberTileGame' do
# Your 'node_modules' directory is probably in the root of your project,
# but if not, adjust the `:path` accordingly
pod 'FBLazyVector', :path => "../node_modules/react-native/Libraries/FBLazyVector"
pod 'FBReactNativeSpec', :path => "../node_modules/react-native/Libraries/FBReactNativeSpec"
pod 'RCTRequired', :path => "../node_modules/react-native/Libraries/RCTRequired"
pod 'RCTTypeSafety', :path => "../node_modules/react-native/Libraries/TypeSafety"
pod 'React', :path => '../node_modules/react-native/'
pod 'React-Core', :path => '../node_modules/react-native/'
pod 'React-CoreModules', :path => '../node_modules/react-native/React/CoreModules'
pod 'React-Core/DevSupport', :path => '../node_modules/react-native/'
pod 'React-RCTActionSheet', :path => '../node_modules/react-native/Libraries/ActionSheetIOS'
pod 'React-RCTAnimation', :path => '../node_modules/react-native/Libraries/NativeAnimation'
pod 'React-RCTBlob', :path => '../node_modules/react-native/Libraries/Blob'
pod 'React-RCTImage', :path => '../node_modules/react-native/Libraries/Image'
pod 'React-RCTLinking', :path => '../node_modules/react-native/Libraries/LinkingIOS'
pod 'React-RCTNetwork', :path => '../node_modules/react-native/Libraries/Network'
pod 'React-RCTSettings', :path => '../node_modules/react-native/Libraries/Settings'
pod 'React-RCTText', :path => '../node_modules/react-native/Libraries/Text'
pod 'React-RCTVibration', :path => '../node_modules/react-native/Libraries/Vibration'
pod 'React-Core/RCTWebSocket', :path => '../node_modules/react-native/'
pod 'React-cxxreact', :path => '../node_modules/react-native/ReactCommon/cxxreact'
pod 'React-jsi', :path => '../node_modules/react-native/ReactCommon/jsi'
pod 'React-jsiexecutor', :path => '../node_modules/react-native/ReactCommon/jsiexecutor'
pod 'React-jsinspector', :path => '../node_modules/react-native/ReactCommon/jsinspector'
pod 'ReactCommon/callinvoker', :path => "../node_modules/react-native/ReactCommon"
pod 'ReactCommon/turbomodule/core', :path => "../node_modules/react-native/ReactCommon"
pod 'Yoga', :path => '../node_modules/react-native/ReactCommon/yoga'
pod 'DoubleConversion', :podspec => '../node_modules/react-native/third-party-podspecs/DoubleConversion.podspec'
pod 'glog', :podspec => '../node_modules/react-native/third-party-podspecs/glog.podspec'
pod 'Folly', :podspec => '../node_modules/react-native/third-party-podspecs/Folly.podspec'
end
After you have created your Podfile
, you are ready to install the React Native pod.
$ pod install
You should see output such as:
Analyzing dependencies
Fetching podspec for `React` from `../node_modules/react-native`
Downloading dependencies
Installing React (0.62.0)
Generating Pods project
Integrating client project
Sending stats
Pod installation complete! There are 3 dependencies from the Podfile and 1 total pod installed.
If this fails with errors mentioning
xcrun
, make sure that in Xcode in Settings... (or Preferences...) > Locations the Command Line Tools are assigned.
Code integration
Now we will actually modify the native iOS application to integrate React Native. For our 2048 sample app, we will add a "High Score" screen in React Native.
The React Native component
The first bit of code we will write is the actual React Native code for the new "High Score" screen that will be integrated into our application.
1. 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 require
s other file that are part of your React Native component or application, or it can contain all the code that is needed for it. In our case, we will put everything in index.js
.
2. Add your React Native code
In your index.js
, create your component. In our sample here, we will add a <Text>
component within a styled <View>
import React from 'react';
import {AppRegistry, StyleSheet, Text, View} from 'react-native';
const RNHighScores = ({scores}) => {
const contents = scores.map(score => (
<Text key={score.name}>
{score.name}:{score.value}
{'\n'}
</Text>
));
return (
<View style={styles.container}>
<Text style={styles.highScoresTitle}>
2048 High Scores!
</Text>
<Text style={styles.scores}>{contents}</Text>
</View>
);
};
const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: 'center',
alignItems: 'center',
backgroundColor: '#FFFFFF',
},
highScoresTitle: {
fontSize: 20,
textAlign: 'center',
margin: 10,
},
scores: {
textAlign: 'center',
color: '#333333',
marginBottom: 5,
},
});
// Module name
AppRegistry.registerComponent('RNHighScores', () => RNHighScores);
RNHighScores
is the name of your module that will be used when you add a view to React Native from within your iOS application.
The Magic: RCTRootView
Now that your React Native component is created via index.js
, you need to add that component to a new or existing ViewController
. The easiest path to take is to optionally create an event path to your component and then add that component to an existing ViewController
.
We will tie our React Native component with a new native view in the ViewController
that will actually contain it called RCTRootView
.
1. Create an Event Path
You can add a new link on the main game menu to go to the "High Score" React Native page.
2. Event Handler
We will now add an event handler from the menu link. A method will be added to the main ViewController
of your application. This is where RCTRootView
comes into play.
When you build a React Native application, you use the Metro bundler to create an index.bundle
that will be served by the React Native server. Inside index.bundle
will be our RNHighScore
module. So, we need to point our RCTRootView
to the location of the index.bundle
resource (via NSURL
) and tie it to the module.
We will, for debugging purposes, log that the event handler was invoked. Then, we will create a string with the location of our React Native code that exists inside the index.bundle
. Finally, we will create the main RCTRootView
. Notice how we provide RNHighScores
as the moduleName
that we created above when writing the code for our React Native component.
First import
the RCTRootView
header.
#import <React/RCTRootView.h>
The
initialProperties
are here for illustration purposes so we have some data for our high score screen. In our React Native component, we will usethis.props
to get access to that data.
- (IBAction)highScoreButtonPressed:(id)sender {
NSLog(@"High Score Button Pressed");
NSURL *jsCodeLocation = [NSURL URLWithString:@"http://localhost:8081/index.bundle?platform=ios"];
RCTRootView *rootView =
[[RCTRootView alloc] initWithBundleURL: jsCodeLocation
moduleName: @"RNHighScores"
initialProperties:
@{
@"scores" : @[
@{
@"name" : @"Alex",
@"value": @"42"
},
@{
@"name" : @"Joel",
@"value": @"10"
}
]
}
launchOptions: nil];
UIViewController *vc = [[UIViewController alloc] init];
vc.view = rootView;
[self presentViewController:vc animated:YES completion:nil];
}
Note that
RCTRootView initWithURL
starts up a new JSC VM. To save resources and simplify the communication between RN views in different parts of your native app, you can have multiple views powered by React Native that are associated with a single JS runtime. To do that, instead of using[RCTRootView alloc] initWithURL
, useRCTBridge initWithBundleURL
to create a bridge and then useRCTRootView initWithBridge
.
When moving your app to production, the
NSURL
can point to a pre-bundled file on disk via something like[[NSBundle mainBundle] URLForResource:@"main" withExtension:@"jsbundle"];
. You can use thereact-native-xcode.sh
script innode_modules/react-native/scripts/
to generate that pre-bundled file.
3. Wire Up
Wire up the new link in the main menu to the newly added event handler method.
One of the easier ways to do this is to open the view in the storyboard and right click on the new link. Select something such as the
Touch Up Inside
event, drag that to the storyboard and then select the created method from the list provided.
Test your integration
You have now done all the basic steps to integrate React Native with your current application. Now we will start the Metro bundler to build the index.bundle
package and the server running on localhost
to serve it.
1. Add App Transport Security exception
Apple has blocked implicit cleartext HTTP resource loading. So we need to add the following our project's Info.plist
(or equivalent) file.
<key>NSAppTransportSecurity</key>
<dict>
<key>NSExceptionDomains</key>
<dict>
<key>localhost</key>
<dict>
<key>NSTemporaryExceptionAllowsInsecureHTTPLoads</key>
<true/>
</dict>
</dict>
</dict>
App Transport Security is good for your users. Make sure to re-enable it prior to releasing your app for production.
2. Run the packager
To run your app, you need to first start the development server. To do this, run the following command in the root directory of your React Native project:
- npm
- Yarn
npm start
yarn start
3. Run the app
If you are using Xcode or your favorite editor, build and run your native iOS application as normal. Alternatively, you can run the app from the command line using:
- npm
- Yarn
npm run ios
yarn ios
In our sample application, you should see the link to the "High Scores" and then when you click on that you will see the rendering of your React Native component.
Here is the native application home screen:
Here is the React Native high score screen:
If you are getting module resolution issues when running your application please see this GitHub issue for information and possible resolution. This comment seemed to be the latest possible resolution.
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.
Key Concepts
The keys to integrating React Native components into your iOS application are to:
- Set up React Native dependencies and directory structure.
- Understand what React Native components you will use in your app.
- Add these components as dependencies using CocoaPods.
- Develop your React Native components in JavaScript.
- Add a
RCTRootView
to your iOS app. This view will serve as the container for your React Native component. - Start the React Native server and run your native application.
- Verify that the React Native aspect of your application works as expected.
Prerequisites
Follow the React Native CLI Quickstart in the environment setup guide to configure your development environment for building React Native apps for iOS.
1. Set up directory structure
To ensure a smooth experience, create a new folder for your integrated React Native project, then copy your existing iOS project to a /ios
subfolder.
2. Install JavaScript dependencies
Go to the root directory for your project and create a new package.json
file with the following contents:
{
"name": "MyReactNativeApp",
"version": "0.0.1",
"private": true,
"scripts": {
"start": "yarn react-native start"
}
}
Next, install the react
and react-native
packages. Open a terminal or command prompt, then navigate to the directory with your package.json
file and run:
- npm
- Yarn
npm install react-native
yarn add react-native
This will print a message similar to the following (scroll up in the installation command output to see it):
warning "
react-native@0.52.2
" has unmet peer dependency "react@16.2.0
".
This is OK, it means we also need to install React:
- npm
- Yarn
npm install react@version_printed_above
yarn add react@version_printed_above
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.
3. Install CocoaPods
CocoaPods is a package management tool for iOS and macOS development. We use it to add the actual React Native framework code locally into your current project.
We recommend installing CocoaPods using Homebrew.
$ brew install cocoapods
It is technically possible not to use CocoaPods, but that would require manual library and linker additions that would overly complicate this process.
Adding React Native to your app
Assume the app for integration is a 2048 game. Here is what the main menu of the native application looks like without React Native.
Command Line Tools for Xcode
Install the Command Line Tools. Choose Settings... (or Preferences...) in the Xcode menu. Go to the Locations panel and install the tools by selecting the most recent version in the Command Line Tools dropdown.
Configuring CocoaPods dependencies
Before you integrate React Native into your application, you will want to decide what parts of the React Native framework you would like to integrate. We will use CocoaPods to specify which of these "subspecs" your app will depend on.
The list of supported subspec
s is available in /node_modules/react-native/React.podspec
. They are generally named by functionality. For example, you will generally always want the Core
subspec
. That will get you the AppRegistry
, StyleSheet
, View
and other core React Native libraries. If you want to add the React Native Text
library (e.g., for <Text>
elements), then you will need the RCTText
subspec
. If you want the Image
library (e.g., for <Image>
elements), then you will need the RCTImage
subspec
.
You can specify which subspec
s your app will depend on in a Podfile
file. The easiest way to create a Podfile
is by running the CocoaPods init
command in the /ios
subfolder of your project:
$ pod init
The Podfile
will contain a boilerplate setup that you will tweak for your integration purposes.
The
Podfile
version changes depending on your version ofreact-native
. Refer to https://react-native-community.github.io/upgrade-helper/ for the specific version ofPodfile
you should be using.
Ultimately, your Podfile
should look something similar to this:
Podfile Template
After you have created your Podfile
, you are ready to install the React Native pod.
$ pod install
You should see output such as:
Analyzing dependencies
Fetching podspec for `React` from `../node_modules/react-native`
Downloading dependencies
Installing React (0.62.0)
Generating Pods project
Integrating client project
Sending stats
Pod installation complete! There are 3 dependencies from the Podfile and 1 total pod installed.
If this fails with errors mentioning
xcrun
, make sure that in Xcode in Settings... (or Preferences...) > Locations the Command Line Tools are assigned.
If you get a warning such as "The
swift-2048 [Debug]
target overrides theFRAMEWORK_SEARCH_PATHS
build setting defined inPods/Target Support Files/Pods-swift-2048/Pods-swift-2048.debug.xcconfig
. This can lead to problems with the CocoaPods installation", then make sure theFramework Search Paths
inBuild Settings
for bothDebug
andRelease
only contain$(inherited)
.
Code integration
Now we will actually modify the native iOS application to integrate React Native. For our 2048 sample app, we will add a "High Score" screen in React Native.
The React Native component
The first bit of code we will write is the actual React Native code for the new "High Score" screen that will be integrated into our application.
1. 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 require
s other file that are part of your React Native component or application, or it can contain all the code that is needed for it. In our case, we will put everything in index.js
.
2. Add your React Native code
In your index.js
, create your component. In our sample here, we will add a <Text>
component within a styled <View>
import React from 'react';
import {AppRegistry, StyleSheet, Text, View} from 'react-native';
const RNHighScores = ({scores}) => {
const contents = scores.map(score => (
<Text key={score.name}>
{score.name}:{score.value}
{'\n'}
</Text>
));
return (
<View style={styles.container}>
<Text style={styles.highScoresTitle}>
2048 High Scores!
</Text>
<Text style={styles.scores}>{contents}</Text>
</View>
);
};
const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: 'center',
alignItems: 'center',
backgroundColor: '#FFFFFF',
},
highScoresTitle: {
fontSize: 20,
textAlign: 'center',
margin: 10,
},
scores: {
textAlign: 'center',
color: '#333333',
marginBottom: 5,
},
});
// Module name
AppRegistry.registerComponent('RNHighScores', () => RNHighScores);
RNHighScores
is the name of your module that will be used when you add a view to React Native from within your iOS application.
The Magic: RCTRootView
Now that your React Native component is created via index.js
, you need to add that component to a new or existing ViewController
. The easiest path to take is to optionally create an event path to your component and then add that component to an existing ViewController
.
We will tie our React Native component with a new native view in the ViewController
that will actually contain it called RCTRootView
.
1. Create an Event Path
You can add a new link on the main game menu to go to the "High Score" React Native page.
2. Event Handler
We will now add an event handler from the menu link. A method will be added to the main ViewController
of your application. This is where RCTRootView
comes into play.
When you build a React Native application, you use the Metro bundler to create an index.bundle
that will be served by the React Native server. Inside index.bundle
will be our RNHighScore
module. So, we need to point our RCTRootView
to the location of the index.bundle
resource (via NSURL
) and tie it to the module.
We will, for debugging purposes, log that the event handler was invoked. Then, we will create a string with the location of our React Native code that exists inside the index.bundle
. Finally, we will create the main RCTRootView
. Notice how we provide RNHighScores
as the moduleName
that we created above when writing the code for our React Native component.
First import
the React
library.
import React
The
initialProperties
are here for illustration purposes so we have some data for our high score screen. In our React Native component, we will usethis.props
to get access to that data.
@IBAction func highScoreButtonTapped(sender : UIButton) {
NSLog("Hello")
let jsCodeLocation = URL(string: "http://localhost:8081/index.bundle?platform=ios")
let mockData:NSDictionary = ["scores":
[
["name":"Alex", "value":"42"],
["name":"Joel", "value":"10"]
]
]
let rootView = RCTRootView(
bundleURL: jsCodeLocation,
moduleName: "RNHighScores",
initialProperties: mockData as [NSObject : AnyObject],
launchOptions: nil
)
let vc = UIViewController()
vc.view = rootView
self.present(vc, animated: true, completion: nil)
}
Note that
RCTRootView bundleURL
starts up a new JSC VM. To save resources and simplify the communication between RN views in different parts of your native app, you can have multiple views powered by React Native that are associated with a single JS runtime. To do that, instead of usingRCTRootView bundleURL
, useRCTBridge initWithBundleURL
to create a bridge and then useRCTRootView initWithBridge
.
When moving your app to production, the
NSURL
can point to a pre-bundled file on disk via something likelet mainBundle = NSBundle(URLForResource: "main" withExtension:"jsbundle")
. You can use thereact-native-xcode.sh
script innode_modules/react-native/scripts/
to generate that pre-bundled file.
3. Wire Up
Wire up the new link in the main menu to the newly added event handler method.
One of the easier ways to do this is to open the view in the storyboard and right click on the new link. Select something such as the
Touch Up Inside
event, drag that to the storyboard and then select the created method from the list provided.
3. Window Reference
Add an window reference to your AppDelegate.swift file. Ultimately, your AppDelegate should look something similar to this:
import UIKit
@main
class AppDelegate: UIResponder, UIApplicationDelegate {
// Add window reference
var window: UIWindow?
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
// Override point for customization after application launch.
return true
}
....
}
Test your integration
You have now done all the basic steps to integrate React Native with your current application. Now we will start the Metro bundler to build the index.bundle
package and the server running on localhost
to serve it.
1. Add App Transport Security exception
Apple has blocked implicit cleartext HTTP resource loading. So we need to add the following our project's Info.plist
(or equivalent) file.
<key>NSAppTransportSecurity</key>
<dict>
<key>NSExceptionDomains</key>
<dict>
<key>localhost</key>
<dict>
<key>NSTemporaryExceptionAllowsInsecureHTTPLoads</key>
<true/>
</dict>
</dict>
</dict>
App Transport Security is good for your users. Make sure to re-enable it prior to releasing your app for production.
2. Run the packager
To run your app, you need to first start the development server. To do this, run the following command in the root directory of your React Native project:
- npm
- Yarn
npm start
yarn start
3. Run the app
If you are using Xcode or your favorite editor, build and run your native iOS application as normal. Alternatively, you can run the app from the command line using following command from the root directory of your React Native project:
- npm
- Yarn
npm run ios
yarn ios
In our sample application, you should see the link to the "High Scores" and then when you click on that you will see the rendering of your React Native component.
Here is the native application home screen:
Here is the React Native high score screen:
If you are getting module resolution issues when running your application please see this GitHub issue for information and possible resolution. This comment seemed to be the latest possible resolution.
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.