Lifecycle Hooks Reference

Module Lifecycle (in module definition)

OnCreate {
  // Module initialized - preferred over class initializers
}

OnDestroy {
  // Module deallocated - clean up resources
}

OnAppContextDestroys {
  // App context is being deallocated
}

iOS App Lifecycle (in module definition)

OnAppEntersForeground { /* UIApplication.willEnterForegroundNotification */ }
OnAppEntersBackground { /* UIApplication.didEnterBackgroundNotification */ }
OnAppBecomesActive { /* UIApplication.didBecomeActiveNotification */ }

Android Activity Lifecycle (in module definition)

OnActivityEntersForeground { /* Activity resumed */ }
OnActivityEntersBackground { /* Activity paused */ }
OnActivityDestroys { /* Activity destroyed */ }
OnNewIntent { intent -> /* Deep link received */ }
OnActivityResult { activity, result -> /* startActivityForResult callback */ }
OnUserLeavesActivity { /* User-initiated background transition */ }
RegisterActivityContracts { /* Modern activity result contracts */ }

iOS AppDelegate Subscribers

For hooking into AppDelegate events without editing AppDelegate directly. Requires app's AppDelegate to extend ExpoAppDelegate.

import ExpoModulesCore

public class MyAppDelegateSubscriber: ExpoAppDelegateSubscriber {
  public func applicationDidBecomeActive(_ application: UIApplication) {}
  public func applicationWillResignActive(_ application: UIApplication) {}
  public func applicationDidEnterBackground(_ application: UIApplication) {}
  public func applicationWillEnterForeground(_ application: UIApplication) {}
  public func applicationWillTerminate(_ application: UIApplication) {}

  public func application(
    _ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
  ) -> Bool {
    return false  // Return true if handled
  }
}

{
  "apple": {
    "appDelegateSubscribers": ["MyAppDelegateSubscriber"]
  }
}

Result aggregation:

didFinishLaunchingWithOptions: Returns true if any subscriber returns true
didReceiveRemoteNotification: Priority: failed > newData > noData

Android Lifecycle Listeners

For hooking into Activity/Application lifecycle outside module definitions. Useful for handling deep links, intents, and app-level initialization.

ReactActivityLifecycleListener

Supported callbacks: onCreate, onResume, onPause, onDestroy, onNewIntent, onBackPressed.

Note: onStart and onStop are not supported — the implementation hooks into ReactActivityDelegate which lacks these methods.

class MyPackage : Package {
  override fun createReactActivityLifecycleListeners(
    activityContext: Context
  ): List<ReactActivityLifecycleListener> {
    return listOf(MyActivityListener())
  }
}

class MyActivityListener : ReactActivityLifecycleListener {
  override fun onCreate(activity: Activity, savedInstanceState: Bundle?) { }
  override fun onResume(activity: Activity) { }
  override fun onPause(activity: Activity) { }
  override fun onDestroy(activity: Activity) { }
  override fun onNewIntent(intent: Intent?): Boolean { return false }
  override fun onBackPressed(): Boolean { return false }
}

ApplicationLifecycleListener

Supported callbacks: onCreate, onConfigurationChanged.

class MyPackage : Package {
  override fun createApplicationLifecycleListeners(
    context: Context
  ): List<ApplicationLifecycleListener> {
    return listOf(MyAppListener())
  }
}

class MyAppListener : ApplicationLifecycleListener {
  override fun onCreate(application: Application) {
    // App-level initialization
  }
}

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