react-native/Libraries/AppState/AppState.js

143 lines
3.9 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 AppState
* @flow
*/
'use strict';
var Map = require('Map');
var NativeModules = require('NativeModules');
var RCTDeviceEventEmitter = require('RCTDeviceEventEmitter');
var RCTAppState = NativeModules.AppState;
var logError = require('logError');
var invariant = require('fbjs/lib/invariant');
var _eventHandlers = {
change: new Map(),
memoryWarning: new Map(),
};
/**
* `AppState` can tell you if the app is in the foreground or background,
* and notify you when the state changes.
*
* AppState is frequently used to determine the intent and proper behavior when
* handling push notifications.
*
* ### App States
*
* - `active` - The app is running in the foreground
* - `background` - The app is running in the background. The user is either
* in another app or on the home screen
* - `inactive` - This is a transition state that currently never happens for
* typical React Native apps.
*
* For more information, see
* [Apple's documentation](https://developer.apple.com/library/ios/documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/TheAppLifeCycle/TheAppLifeCycle.html)
*
* ### Basic Usage
*
* To see the current state, you can check `AppState.currentState`, which
* will be kept up-to-date. However, `currentState` will be null at launch
* while `AppState` retrieves it over the bridge.
*
* ```
* getInitialState: function() {
* return {
* currentAppState: AppState.currentState,
* };
* },
* componentDidMount: function() {
* AppState.addEventListener('change', this._handleAppStateChange);
* },
* componentWillUnmount: function() {
* AppState.removeEventListener('change', this._handleAppStateChange);
* },
* _handleAppStateChange: function(currentAppState) {
* this.setState({ currentAppState, });
* },
* render: function() {
* return (
* <Text>Current state is: {this.state.currentAppState}</Text>
* );
* },
* ```
*
* This example will only ever appear to say "Current state is: active" because
* the app is only visible to the user when in the `active` state, and the null
* state will happen only momentarily.
*/
var AppState = {
/**
* Add a handler to AppState changes by listening to the `change` event type
* and providing the handler
*/
addEventListener: function(
type: string,
handler: Function
) {
invariant(
['change', 'memoryWarning'].indexOf(type) !== -1,
'Trying to subscribe to unknown event: "%s"', type
);
if (type === 'change') {
_eventHandlers[type].set(handler, RCTDeviceEventEmitter.addListener(
'appStateDidChange',
(appStateData) => {
handler(appStateData.app_state);
}
));
} else if (type === 'memoryWarning') {
_eventHandlers[type].set(handler, RCTDeviceEventEmitter.addListener(
'memoryWarning',
handler
));
}
},
/**
* Remove a handler by passing the `change` event type and the handler
*/
removeEventListener: function(
type: string,
handler: Function
) {
invariant(
['change', 'memoryWarning'].indexOf(type) !== -1,
'Trying to remove listener for unknown event: "%s"', type
);
if (!_eventHandlers[type].has(handler)) {
return;
}
_eventHandlers[type].get(handler).remove();
_eventHandlers[type].delete(handler);
},
currentState: ('active' : ?string),
};
RCTDeviceEventEmitter.addListener(
'appStateDidChange',
(appStateData) => {
AppState.currentState = appStateData.app_state;
}
);
RCTAppState.getCurrentAppState(
(appStateData) => {
AppState.currentState = appStateData.app_state;
},
logError
);
module.exports = AppState;