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Vitalii T
14c207d9e1
Summary: I've noticed that `BackHandler.removeEventListener()` performs two same `indexOf()` calls on an array that is not changing. By removing extra `indexOf` we can slightly improve time complexity of `BackHandler.removeEventListener()` from O(2n) to O(n) ## Changelog <!-- Help reviewers and the release process by writing your own changelog entry. For an example, see: https://reactnative.dev/contributing/changelogs-in-pull-requests --> [Android] [Fixed] - Remove extra indexOf call in BackHandler.removeEventListener Pull Request resolved: https://github.com/facebook/react-native/pull/34281 Test Plan: 1. Add the following code to any function component ```javascript BackHandler.addEventListener('hardwareBackPress', () => true).remove(); ``` 2. Press on hardware back button Expected result: Application closes Reviewed By: dmitryrykun Differential Revision: D38198510 Pulled By: javache fbshipit-source-id: eab6a57689a536623138a4b3ebddbf9ba87d281f
108 lines
2.9 KiB
JavaScript
108 lines
2.9 KiB
JavaScript
/**
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* Copyright (c) Meta Platforms, Inc. and affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*
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* @flow strict-local
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* @format
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*/
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import NativeDeviceEventManager from '../../Libraries/NativeModules/specs/NativeDeviceEventManager';
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import RCTDeviceEventEmitter from '../EventEmitter/RCTDeviceEventEmitter';
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const DEVICE_BACK_EVENT = 'hardwareBackPress';
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type BackPressEventName = 'backPress' | 'hardwareBackPress';
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const _backPressSubscriptions = [];
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RCTDeviceEventEmitter.addListener(DEVICE_BACK_EVENT, function () {
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for (let i = _backPressSubscriptions.length - 1; i >= 0; i--) {
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if (_backPressSubscriptions[i]()) {
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return;
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}
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}
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BackHandler.exitApp();
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});
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/**
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* Detect hardware button presses for back navigation.
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*
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* Android: Detect hardware back button presses, and programmatically invoke the default back button
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* functionality to exit the app if there are no listeners or if none of the listeners return true.
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*
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* iOS: Not applicable.
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*
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* The event subscriptions are called in reverse order (i.e. last registered subscription first),
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* and if one subscription returns true then subscriptions registered earlier will not be called.
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*
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* Example:
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*
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* ```javascript
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* BackHandler.addEventListener('hardwareBackPress', function() {
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* // this.onMainScreen and this.goBack are just examples, you need to use your own implementation here
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* // Typically you would use the navigator here to go to the last state.
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*
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* if (!this.onMainScreen()) {
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* this.goBack();
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* return true;
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* }
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* return false;
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* });
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* ```
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*/
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type TBackHandler = {|
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+exitApp: () => void,
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+addEventListener: (
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eventName: BackPressEventName,
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handler: () => ?boolean,
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) => {remove: () => void, ...},
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+removeEventListener: (
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eventName: BackPressEventName,
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handler: () => ?boolean,
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) => void,
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|};
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const BackHandler: TBackHandler = {
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exitApp: function (): void {
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if (!NativeDeviceEventManager) {
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return;
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}
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NativeDeviceEventManager.invokeDefaultBackPressHandler();
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},
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/**
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* Adds an event handler. Supported events:
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*
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* - `hardwareBackPress`: Fires when the Android hardware back button is pressed.
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*/
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addEventListener: function (
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eventName: BackPressEventName,
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handler: () => ?boolean,
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): {remove: () => void, ...} {
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if (_backPressSubscriptions.indexOf(handler) === -1) {
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_backPressSubscriptions.push(handler);
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}
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return {
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remove: (): void => BackHandler.removeEventListener(eventName, handler),
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};
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},
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/**
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* Removes the event handler.
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*/
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removeEventListener: function (
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eventName: BackPressEventName,
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handler: () => ?boolean,
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): void {
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const index = _backPressSubscriptions.indexOf(handler);
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if (index !== -1) {
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_backPressSubscriptions.splice(index, 1);
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}
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},
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};
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module.exports = BackHandler;
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