react-native/Libraries/Utilities/BackHandler.js.flow

A framework for building native apps using React

/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow strict-local
 * @format
 */

'use strict';

export type BackPressEventName = 'backPress' | 'hardwareBackPress';

/**
 * Event dispatched when the hardware back button is pressed.
 * The `timeStamp` property reflects the native timestamp captured
 * when the back press was emitted.
 */
export interface HardwareBackPressEvent {
  readonly type: string;
  readonly timeStamp: number;
}

type TBackHandler = {
  exitApp(): void,
  addEventListener(
    eventName: BackPressEventName,
    handler: (event: HardwareBackPressEvent) => ?boolean,
  ): {remove: () => void, ...},
};

/**
 * Detect hardware back button presses, and programmatically invoke the
 * default back button functionality to exit the app if there are no
 * listeners or if none of the listeners return true.
 * The event subscriptions are called in reverse order
 * (i.e. last registered subscription first), and if one subscription
 * returns true then subscriptions registered earlier
 * will not be called.
 *
 * @see https://reactnative.dev/docs/backhandler
 */
declare const BackHandler: TBackHandler;

declare export default typeof BackHandler;