react-native/Libraries/Utilities/BackAndroid.android.js

77 lines
1.7 KiB
JavaScript

/**
* Copyright (c) 2015-present, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the BSD-style license found in the
* LICENSE file in the root directory of this source tree. An additional grant
* of patent rights can be found in the PATENTS file in the same directory.
*
* @providesModule BackAndroid
*/
'use strict';
var Set = require('Set');
var DeviceEventManager = require('NativeModules').DeviceEventManager;
var RCTDeviceEventEmitter = require('RCTDeviceEventEmitter');
var DEVICE_BACK_EVENT = 'hardwareBackPress';
type BackPressEventName = $Enum<{
backPress: string;
}>;
var _backPressSubscriptions = new Set();
RCTDeviceEventEmitter.addListener(DEVICE_BACK_EVENT, function() {
var invokeDefault = true;
_backPressSubscriptions.forEach((subscription) => {
if (subscription()) {
invokeDefault = false;
}
});
if (invokeDefault) {
BackAndroid.exitApp();
}
});
/**
* Detect hardware back button presses, and programatically invoke the default back button
* functionality to exit the app if there are no listeners or if none of the listeners return true.
*
* Example:
*
* ```js
* BackAndroid.addEventListener('hardwareBackPress', function() {
* if (!this.onMainScreen()) {
* this.goBack();
* return true;
* }
* return false;
* });
* ```
*/
var BackAndroid = {
exitApp: function() {
DeviceEventManager.invokeDefaultBackPressHandler();
},
addEventListener: function (
eventName: BackPressEventName,
handler: Function
): void {
_backPressSubscriptions.add(handler);
},
removeEventListener: function(
eventName: BackPressEventName,
handler: Function
): void {
_backPressSubscriptions.delete(handler);
},
};
module.exports = BackAndroid;