RN: Simplify `Keyboard`

Summary:
Simplifies `Keyboard` by removing redundant methods and changing `addEventListener` to return an `EventSubscription`.

Changelog:
[General][Changed] - `Keyboard.addListener` now returns an `EventSubscription` object.
[General][Removed] - Removed `Keyboard.removeListener`. Instead, use the `remove()` method on the object returned by `Keyboard.addListener`.
[General][Removed] - `Keyboard` no longer inherits from `NativeEventEmitter`, so it no longer implements `removeAllListeners`, and `removeSubscription`.

Reviewed By: milroc

Differential Revision: D26163536

fbshipit-source-id: b4bd91627cd027a13fcba269a253823913eb7589

Libraries/Components/Keyboard/Keyboard.js

@@ -12,7 +12,7 @@ import NativeEventEmitter from '../../EventEmitter/NativeEventEmitter';
 import LayoutAnimation from '../../LayoutAnimation/LayoutAnimation';
 import dismissKeyboard from '../../Utilities/dismissKeyboard';
 import NativeKeyboardObserver from './NativeKeyboardObserver';
-import type EmitterSubscription from '../../vendor/emitter/_EmitterSubscription';
+import {type EventSubscription} from '../../vendor/emitter/EventEmitter';
 
 export type KeyboardEventName = $Keys<KeyboardEventDefinitions>;
 
@@ -101,10 +101,10 @@ type KeyboardEventDefinitions = {
  *```
  */
 
-class Keyboard extends NativeEventEmitter<KeyboardEventDefinitions> {
-  constructor() {
-    super(NativeKeyboardObserver);
-  }
+class Keyboard {
+  _emitter: NativeEventEmitter<KeyboardEventDefinitions> = new NativeEventEmitter(
+    NativeKeyboardObserver,
+  );
 
   /**
    * The `addListener` function connects a JavaScript function to an identified native
@@ -132,22 +132,9 @@ class Keyboard extends NativeEventEmitter<KeyboardEventDefinitions> {
   addListener<K: $Keys<KeyboardEventDefinitions>>(
     eventType: K,
     listener: (...$ElementType<KeyboardEventDefinitions, K>) => mixed,
-    context: $FlowFixMe,
-  ): EmitterSubscription<KeyboardEventDefinitions, K> {
-    return super.addListener(eventType, listener);
-  }
-
-  /**
-   * Removes a specific listener.
-   *
-   * @param {string} eventName The `nativeEvent` is the string that identifies the event you're listening for.
-   * @param {function} callback function to be called when the event fires.
-   */
-  removeListener<K: $Keys<KeyboardEventDefinitions>>(
-    eventType: K,
-    listener: (...$ElementType<KeyboardEventDefinitions, K>) => mixed,
-  ): void {
-    super.removeListener(eventType, listener);
+    context?: mixed,
+  ): EventSubscription {
+    return this._emitter.addListener(eventType, listener);
   }
 
   /**
@@ -156,7 +143,7 @@ class Keyboard extends NativeEventEmitter<KeyboardEventDefinitions> {
    * @param {string} eventType The native event string listeners are watching which will be removed.
    */
   removeAllListeners<K: $Keys<KeyboardEventDefinitions>>(eventType: ?K): void {
-    super.removeAllListeners(eventType);
+    this._emitter.removeAllListeners(eventType);
   }
 
   /**

Libraries/Components/Keyboard/__tests__/Keyboard-test.js

@@ -9,13 +9,10 @@
  * @emails oncall+react_native
  */
 
-const NativeModules = require('../../../BatchedBridge/NativeModules');
 const LayoutAnimation = require('../../../LayoutAnimation/LayoutAnimation');
 const dismissKeyboard = require('../../../Utilities/dismissKeyboard');
 const Keyboard = require('../Keyboard');
 
-import NativeEventEmitter from '../../../EventEmitter/NativeEventEmitter';
-
 jest.mock('../../../LayoutAnimation/LayoutAnimation');
 jest.mock('../../../Utilities/dismissKeyboard');
 
@@ -24,16 +21,6 @@ describe('Keyboard', () => {
     jest.resetAllMocks();
   });
 
-  it('exposes KeyboardEventEmitter methods', () => {
-    const KeyboardObserver = NativeModules.KeyboardObserver;
-    const KeyboardEventEmitter = new NativeEventEmitter(KeyboardObserver);
-
-    // $FlowFixMe
-    expect(Keyboard._subscriber).toBe(KeyboardEventEmitter._subscriber);
-    // $FlowFixMe Cannot access private property
-    expect(Keyboard._nativeModule).toBe(KeyboardEventEmitter._nativeModule);
-  });
-
   it('uses dismissKeyboard utility', () => {
     Keyboard.dismiss();
     expect(dismissKeyboard).toHaveBeenCalled();