尝试向现有的反应本机库中添加新功能时出现“未定义不是功能”的问题

Question

我正在尝试向名为react-native-system-setting的现有React本机库中添加新功能，对于我的应用程序，我需要能够模拟关键事件，以如{{所述，在不同的媒体播放器上播放，暂停和跳过歌曲3}}，所以我将函数“ MediaControl”添加到here库中：

public SystemSetting(ReactApplicationContext reactContext) {
    super(reactContext);
    mContext = reactContext;
    reactContext.addLifecycleEventListener(this);
    am = (AudioManager) mContext.getApplicationContext().getSystemService(Context.AUDIO_SERVICE);
    wm = (WifiManager) mContext.getApplicationContext().getSystemService(Context.WIFI_SERVICE);
    lm = (LocationManager) mContext.getApplicationContext().getSystemService(Context.LOCATION_SERVICE);

    listenVolume(reactContext);
}

@ReactMethod
public void MediaControl(String Command ) {
long eventtime = SystemClock.uptimeMillis();

    switch (Command) {
        case "next":
            KeyEvent downEvent = new KeyEvent(eventtime, eventtime, KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_MEDIA_NEXT, 0);
            am.dispatchMediaKeyEvent(downEvent);

            KeyEvent upEvent = new KeyEvent(eventtime, eventtime, KeyEvent.ACTION_UP, KeyEvent.KEYCODE_MEDIA_NEXT, 0);
            am.dispatchMediaKeyEvent(upEvent);

        case "previous":
            KeyEvent downEvent = new KeyEvent(eventtime, eventtime, KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_MEDIA_PREVIOUS, 0);
            am.dispatchMediaKeyEvent(downEvent);

            KeyEvent upEvent = new KeyEvent(eventtime, eventtime, KeyEvent.ACTION_UP, KeyEvent.KEYCODE_MEDIA_PREVIOUS, 0);
            am.dispatchMediaKeyEvent(upEvent);

        case "play":
            KeyEvent downEvent = new KeyEvent(eventtime, eventtime, KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_MEDIA_PLAY_PAUSE, 0);
            am.dispatchMediaKeyEvent(downEvent);

        case "pause":
            KeyEvent upEvent = new KeyEvent(eventtime, eventtime, KeyEvent.ACTION_UP, KeyEvent.KEYCODE_MEDIA_PLAY_PAUSE, 0);
            am.dispatchMediaKeyEvent(upEvent);
    }
}

它可以在android studio上正常构建，但是当我尝试使用该功能时，出现错误：

undefined is not a function (evaluating '_reactNativeSystemSetting2.default.MediaControl("play")')

我错过了什么吗？