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c2cf510ff8
Summary: The example of `BackAndroid` caused a bit of confusion for beginners (see #8822), so I thought we should clarify the functionality a bit. I added a comment indicating that a user would have to implement `this.onMainScreen` and `this.goBack` on their own, this was the original problem. Closes https://github.com/facebook/react-native/pull/8829 Differential Revision: D3660332 fbshipit-source-id: d84a29586c6a1a439f386e6b88220d7b0a275129
86 lines
2.1 KiB
JavaScript
86 lines
2.1 KiB
JavaScript
/**
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* Copyright (c) 2015-present, Facebook, Inc.
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* All rights reserved.
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*
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* This source code is licensed under the BSD-style license found in the
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* LICENSE file in the root directory of this source tree. An additional grant
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* of patent rights can be found in the PATENTS file in the same directory.
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*
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* @providesModule BackAndroid
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*/
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'use strict';
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var DeviceEventManager = require('NativeModules').DeviceEventManager;
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var RCTDeviceEventEmitter = require('RCTDeviceEventEmitter');
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var DEVICE_BACK_EVENT = 'hardwareBackPress';
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type BackPressEventName = $Enum<{
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backPress: string;
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}>;
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var _backPressSubscriptions = new Set();
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RCTDeviceEventEmitter.addListener(DEVICE_BACK_EVENT, function() {
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var backPressSubscriptions = new Set(_backPressSubscriptions);
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var invokeDefault = true;
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var subscriptions = [...backPressSubscriptions].reverse();
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for (var 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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BackAndroid.exitApp();
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}
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});
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/**
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* 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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* Example:
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*
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* ```javascript
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* BackAndroid.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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var BackAndroid = {
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exitApp: function() {
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DeviceEventManager.invokeDefaultBackPressHandler();
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},
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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: () => BackAndroid.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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module.exports = BackAndroid;
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