Configuring lifecycle listeners

Learn about the mechanism that allows the Expo Modules API to hook into the lifecycle of your app.

Some Expo libraries need to handle system events such as deep links, push notifications, and configuration changes by implementing Activity/Application or AppDelegate lifecycle callbacks.

The Expo Modules API provides an easy way to manage such callbacks:

• Android
  ApplicationLifecycleDispatcher and ReactActivityHandler forward Application and Activity lifecycle events to registered listeners. Modules can provide ReactActivityLifecycleListener and ApplicationLifecycleListener implementations through a Package class to register callbacks.
• iOS
  ExpoAppDelegate forwards AppDelegate calls to registered subscribers. Modules can provide an ExpoAppDelegateSubscriber implementation to register callbacks.

Using these mechanisms allows modules to register behavior without requiring you to edit native entry points repeatedly.

Configure your native project

Android

To integrate Application lifecycle listeners on Android, forward the onCreate() and onConfigurationChanged() calls from your Application class to ApplicationLifecycleDispatcher:

iOS

To integrate AppDelegate subscribers on iOS, forward the relevant calls to ExpoAppDelegateSubscriberManager in your existing AppDelegate implementation so that subscribers can respond to them:

Alternatively, if your AppDelegate doesn't already extend another class, you can simplify the setup by inheriting from ExpoAppDelegate, which handles the forwarding automatically:

Note: Not all UIApplicationDelegate methods that could cause significant side effects are supported. See the Expo source (ExpoAppDelegate.swift) for the full list of forwarded methods if you need to rely on a specific delegate.

Test your integration

To test if the callbacks are working correctly, install a module that relies on them. Install expo-linking, which uses lifecycle listeners to handle deep links:

Add a listener for deep links in your code and observe the console when opening a deep link:

import * as Linking from 'expo-linking';
import { useEffect } from 'react';

useEffect(() => {
  const listener = Linking.addEventListener('url', ({ url }) => {
    console.log('Received deep link:', url);
  });

  return listener.remove;
}, []);

Run the following command to open a deep link to your app: