58 lines
2.6 KiB
JavaScript
58 lines
2.6 KiB
JavaScript
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import invariant from 'invariant';
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import { NativeEventEmitter, Platform } from 'react-native';
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const nativeEmitterSubscriptionKey = '@@nativeEmitterSubscription@@';
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export class EventEmitter {
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constructor(nativeModule) {
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this._listenerCount = 0;
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this._nativeModule = nativeModule;
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this._eventEmitter = new NativeEventEmitter(nativeModule);
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}
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addListener(eventName, listener) {
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if (!this._listenerCount && Platform.OS !== 'ios' && this._nativeModule.startObserving) {
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this._nativeModule.startObserving();
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}
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this._listenerCount++;
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const nativeEmitterSubscription = this._eventEmitter.addListener(eventName, listener);
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const subscription = {
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[nativeEmitterSubscriptionKey]: nativeEmitterSubscription,
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remove: () => {
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this.removeSubscription(subscription);
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},
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};
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return subscription;
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}
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removeAllListeners(eventName) {
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// @ts-ignore: the EventEmitter interface has been changed in react-native@0.64.0
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const removedListenerCount = this._eventEmitter.listenerCount
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? // @ts-ignore: this is available since 0.64
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this._eventEmitter.listenerCount(eventName)
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: // @ts-ignore: this is available in older versions
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this._eventEmitter.listeners(eventName).length;
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this._eventEmitter.removeAllListeners(eventName);
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this._listenerCount -= removedListenerCount;
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invariant(this._listenerCount >= 0, `EventEmitter must have a non-negative number of listeners`);
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if (!this._listenerCount && Platform.OS !== 'ios' && this._nativeModule.stopObserving) {
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this._nativeModule.stopObserving();
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}
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}
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removeSubscription(subscription) {
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const nativeEmitterSubscription = subscription[nativeEmitterSubscriptionKey];
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if (!nativeEmitterSubscription) {
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return;
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}
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this._eventEmitter.removeSubscription(nativeEmitterSubscription);
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this._listenerCount--;
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// Ensure that the emitter's internal state remains correct even if `removeSubscription` is
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// called again with the same subscription
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delete subscription[nativeEmitterSubscriptionKey];
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// Release closed-over references to the emitter
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subscription.remove = () => { };
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if (!this._listenerCount && Platform.OS !== 'ios' && this._nativeModule.stopObserving) {
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this._nativeModule.stopObserving();
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}
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}
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emit(eventName, ...params) {
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this._eventEmitter.emit(eventName, ...params);
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}
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}
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//# sourceMappingURL=EventEmitter.js.map
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