BackHandler

The Backhandler API detects hardware button presses for back navigation, lets you register event listeners for the system's back action, and lets you control how your application responds. It is Android-only.

The event subscriptions are called in reverse order (i.e. the last registered subscription is called first).

• If one subscription returns true, then subscriptions registered earlier will not be called.
• If no subscription returns true or none are registered, it programmatically invokes the default back button functionality to exit the app.

Warning for modal users: If your app shows an opened Modal, BackHandler will not publish any events (see Modal docs).

Pattern

BackHandler.addEventListener('hardwareBackPress', function () {
  /**
   * this.onMainScreen and this.goBack are just examples,
   * you need to use your own implementation here.
   *
   * Typically you would use the navigator here to go to the last state.
   */

  if (!this.onMainScreen()) {
    this.goBack();
    /**
     * When true is returned the event will not be bubbled up
     * & no other back action will execute
     */
    return true;
  }
  /**
   * Returning false will let the event to bubble up & let other event listeners
   * or the system's default back action to be executed.
   */
  return false;
});

The following example implements a scenario where you confirm if the user wants to exit the app:

• Function Component
• Class Component

BackHandler.addEventListener creates an event listener & returns a NativeEventSubscription object which should be cleared using NativeEventSubscription.remove method.

Additionally BackHandler.removeEventListener can also be used to clear the event listener. Ensure the callback has the reference to the same function used in the addEventListener call as shown the following example ﹣

• Function Component
• Class Component

Usage with React Navigation

If you are using React Navigation to navigate across different screens, you can follow their guide on Custom Android back button behaviour

Backhandler hook

React Native Hooks has a nice useBackHandler hook which will simplify the process of setting up event listeners.

Reference

Methods

addEventListener()

static addEventListener(eventName, handler)

exitApp()

static exitApp()

removeEventListener()

static removeEventListener(eventName, handler)