124 lines
3.3 KiB
JavaScript
124 lines
3.3 KiB
JavaScript
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/**
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* Copyright (c) Facebook, Inc. and its 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
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* @format
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*/
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// On Apple TV, this implements back navigation using the TV remote's menu button.
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// On iOS, this just implements a stub.
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'use strict';
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const Platform = require('./Platform');
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const TVEventHandler = require('../Components/AppleTV/TVEventHandler');
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type BackPressEventName = 'backPress' | 'hardwareBackPress';
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function emptyFunction(): void {}
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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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* tvOS: Detect presses of the menu button on the TV remote. (Still to be implemented:
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* programmatically disable menu button handling
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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: Function,
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) => {remove: () => void, ...},
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+removeEventListener: (
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eventName: BackPressEventName,
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handler: Function,
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) => void,
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|};
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let BackHandler: TBackHandler;
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if (Platform.isTV) {
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const _tvEventHandler = new TVEventHandler();
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const _backPressSubscriptions = new Set();
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_tvEventHandler.enable(this, function(cmp, evt) {
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if (evt && evt.eventType === 'menu') {
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let invokeDefault = true;
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const subscriptions = Array.from(
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_backPressSubscriptions.values(),
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).reverse();
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for (let i = 0; i < subscriptions.length; ++i) {
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if (subscriptions[i]()) {
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invokeDefault = false;
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break;
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}
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}
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if (invokeDefault) {
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BackHandler.exitApp();
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}
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}
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});
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BackHandler = {
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exitApp: emptyFunction,
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addEventListener: function(
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eventName: BackPressEventName,
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handler: Function,
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): {remove: () => void, ...} {
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_backPressSubscriptions.add(handler);
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return {
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remove: () => BackHandler.removeEventListener(eventName, handler),
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};
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},
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removeEventListener: function(
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eventName: BackPressEventName,
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handler: Function,
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): void {
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_backPressSubscriptions.delete(handler);
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},
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};
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} else {
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BackHandler = {
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exitApp: emptyFunction,
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addEventListener(_eventName: BackPressEventName, _handler: Function) {
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return {
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remove: emptyFunction,
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};
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},
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removeEventListener(_eventName: BackPressEventName, _handler: Function) {},
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};
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}
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module.exports = BackHandler;
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