react-native/Libraries/AppState/AppState.js

148 lines
4.7 KiB
JavaScript

/**
* Copyright (c) Facebook, Inc. and its affiliates.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*
* @format
* @flow
*/
'use strict';
const MissingNativeEventEmitterShim = require('MissingNativeEventEmitterShim');
const NativeEventEmitter = require('NativeEventEmitter');
const NativeModules = require('NativeModules');
const RCTAppState = NativeModules.AppState;
const logError = require('logError');
const invariant = require('fbjs/lib/invariant');
/**
* `AppState` can tell you if the app is in the foreground or background,
* and notify you when the state changes.
*
* See http://facebook.github.io/react-native/docs/appstate.html
*/
class AppState extends NativeEventEmitter {
_eventHandlers: Object;
currentState: ?string;
isAvailable: boolean = true;
constructor() {
super(RCTAppState);
this.isAvailable = true;
this._eventHandlers = {
change: new Map(),
memoryWarning: new Map(),
};
// TODO: Remove the 'active' fallback after `initialAppState` is exported by
// the Android implementation.
this.currentState = RCTAppState.initialAppState || 'active';
let eventUpdated = false;
// TODO: this is a terrible solution - in order to ensure `currentState`
// prop is up to date, we have to register an observer that updates it
// whenever the state changes, even if nobody cares. We should just
// deprecate the `currentState` property and get rid of this.
this.addListener('appStateDidChange', appStateData => {
eventUpdated = true;
this.currentState = appStateData.app_state;
});
// TODO: see above - this request just populates the value of `currentState`
// when the module is first initialized. Would be better to get rid of the
// prop and expose `getCurrentAppState` method directly.
RCTAppState.getCurrentAppState(appStateData => {
// It's possible that the state will have changed here & listeners need to be notified
if (!eventUpdated && this.currentState !== appStateData.app_state) {
this.currentState = appStateData.app_state;
this.emit('appStateDidChange', appStateData);
}
}, logError);
}
// TODO: now that AppState is a subclass of NativeEventEmitter, we could
// deprecate `addEventListener` and `removeEventListener` and just use
// addListener` and `listener.remove()` directly. That will be a breaking
// change though, as both the method and event names are different
// (addListener events are currently required to be globally unique).
/**
* Add a handler to AppState changes by listening to the `change` event type
* and providing the handler.
*
* See http://facebook.github.io/react-native/docs/appstate.html#addeventlistener
*/
addEventListener(type: string, handler: Function) {
invariant(
['change', 'memoryWarning'].indexOf(type) !== -1,
'Trying to subscribe to unknown event: "%s"',
type,
);
if (type === 'change') {
this._eventHandlers[type].set(
handler,
this.addListener('appStateDidChange', appStateData => {
handler(appStateData.app_state);
}),
);
} else if (type === 'memoryWarning') {
this._eventHandlers[type].set(
handler,
this.addListener('memoryWarning', handler),
);
}
}
/**
* Remove a handler by passing the `change` event type and the handler.
*
* See http://facebook.github.io/react-native/docs/appstate.html#removeeventlistener
*/
removeEventListener(type: string, handler: Function) {
invariant(
['change', 'memoryWarning'].indexOf(type) !== -1,
'Trying to remove listener for unknown event: "%s"',
type,
);
if (!this._eventHandlers[type].has(handler)) {
return;
}
this._eventHandlers[type].get(handler).remove();
this._eventHandlers[type].delete(handler);
}
}
if (__DEV__ && !RCTAppState) {
class MissingNativeAppStateShim extends MissingNativeEventEmitterShim {
constructor() {
super('RCTAppState', 'AppState');
}
get currentState(): ?string {
this.throwMissingNativeModule();
}
addEventListener(...args: Array<any>) {
this.throwMissingNativeModule();
}
removeEventListener(...args: Array<any>) {
this.throwMissingNativeModule();
}
}
// This module depends on the native `RCTAppState` module. If you don't
// include it, `AppState.isAvailable` will return `false`, and any method
// calls will throw. We reassign the class variable to keep the autodoc
// generator happy.
AppState = new MissingNativeAppStateShim();
} else {
AppState = new AppState();
}
module.exports = AppState;