Android onfocuschangelistener未响应所有音频管理器更改

我在下面的链接中问了一个问题 我得到了一个完美的答案。我附上了它的代码。现在我的问题是，当音乐开始播放时，我会失去音频焦点。我的onfocuschange侦听器没有响应audio manager中的更改。我的代码有什么错误吗。这样我就可以在音频管理器中收听所有更改开始、暂停、停止。谢谢你的帮助

我在我的服务类中实现了它

am = (AudioManager) getApplicationContext().getSystemService(Context.AUDIO_SERVICE);

    am.getMode();

      afChangeListener = new OnAudioFocusChangeListener() {


            public void onAudioFocusChange(int focusChange) {
                Log.d("new","focus: " +focusChange+"mode "+am.getMode() +"ismusic "+am.isMusicActive());


                if (focusChange == AudioManager.AUDIOFOCUS_GAIN_TRANSIENT){
                    Log.d("new","focus:started trans " );

                }else if (focusChange == AudioManager.AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK){
                    Log.d("new","focus:started duck " );

                }

            else if (focusChange == AudioManager.AUDIOFOCUS_LOSS_TRANSIENT){
                   Log.d("new","focus:paused  " );
            } else if (focusChange == AudioManager.AUDIOFOCUS_GAIN) {
                Log.d("new","focus:started " );
                } else if (focusChange == AudioManager.AUDIOFOCUS_LOSS) {
                    Log.d("new","focus:stoped  " );
                   // am.unregisterMediaButtonEventReceiver(RemoteControlReceiver);
                   // am.abandonAudioFocus(afChangeListener);
                    // Stop playback
                }
            }
        };