java - Android AudioFocus onAudioFocusChange 不监听更改

Question

我一直在构建一个 MediaPlayer 应用程序，我一直在尝试让我的 Mediaplayer 应用程序来处理 AudioFocusChange 事件。但是，无论我如何构建我的代码，我似乎都不会监听 AudioFocusChange 事件，并将继续在其他应用程序之上播放。一切正常，除了当我在我的应用程序中单击播放按钮时，它只是在其他音乐应用程序之上播放音乐而不暂停它。我试过

public void play() {
Intent("com.android.music.musicservicecommand");
        i.putExtra("command", "pause");
        MainActivity.this.sendBroadcast(i);
        int requestAudioFocus = AM.requestAudioFocus(afChangeListener, AudioManager.AUDIOFOCUS_GAIN, AudioManager.STREAM_MUSIC);
        if (requestAudioFocus == AudioManager.AUDIOFOCUS_REQUEST_GRANTED) {
            Toast.makeText(this, "Focus Granted", Toast.LENGTH_SHORT).show();
            if (!mediaPlayer.isPlaying() || mediaPlayer == null) {
                mediaPlayer.start();
                handler.removeCallbacks(moveSeekBarThread);
                handler.postDelayed(moveSeekBarThread, 300);
            }
        } else {
            Toast.makeText(this, "Focus Not Granted", Toast.LENGTH_LONG).show();
            return;
        }
    }

在我的 play() 方法的顶部，但它仍然在该方法之上播放其他应用程序的音乐。

到目前为止，我有:

public class MainActivity extends AppCompatActivity implements             
AudioManager.OnAudioFocusChangeListener {

...

}

其次是监听器 block :

@Override
    public void onAudioFocusChange(int focusChange) {
        switch (focusChange) {
            case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT:
                Toast.makeText(this, "FOCUS LOSS TRANSIENT", Toast.LENGTH_SHORT).show();
                pause();
                break;
            case AudioManager.AUDIOFOCUS_LOSS:
                pause();
                Toast.makeText(this, "FOCUS LOST", Toast.LENGTH_SHORT).show();
                break;
            case AudioManager.AUDIOFOCUS_GAIN_TRANSIENT:
                Intent i = new Intent("com.android.music.musicservicecommand");
                i.putExtra("command", "pause");
                MainActivity.this.sendBroadcast(i);
                AM.setStreamVolume(AudioManager.STREAM_MUSIC, AM.getStreamMaxVolume(AudioManager.STREAM_MUSIC), 0);
                play();
            case AudioManager.AUDIOFOCUS_REQUEST_FAILED:
                stop();
                break;
            case AudioManager.AUDIOFOCUS_REQUEST_GRANTED:
                Intent iARG = new Intent("com.android.music.musicservicecommand");
                iARG.putExtra("command", "pause");
                MainActivity.this.sendBroadcast(iARG);
                AM.setStreamVolume(AudioManager.STREAM_MUSIC, AM.getStreamMaxVolume(AudioManager.STREAM_MUSIC), 0);
                play();
                break;
        }
    }

我还尝试在类声明之外实现并指定一个

AudioManager.OnAudioFocusChangeListener = new onAudioFocusChangeListener(){
public void onAudioFocusChange(int focusChange){
...
}

然而，作为一个全局函数，它也没有监听 focusChange 的

Toasts 在每个 switch case 中实现，以通知我焦点状态何时更改，但我从未看到它们的任何通知。我也尝试输入方法:

int requestAudioFocus = AM.requestAudioFocus(null, AudioManager.AUDIOFOCUS_GAIN, AudioManager.STREAM_MUSIC);
        if (requestAudioFocus == AudioManager.AUDIOFOCUS_REQUEST_GRANTED) {
            Intent i = new Intent("com.android.music.musicservicecommand");
            i.putExtra("command", "pause");
            MainActivity.this.sendBroadcast(i);
}

但是，它只会阻止另一个应用程序中的音乐播放一次。我有一种感觉，我忽略了一些简单的事情，我就是无法让它发挥作用。

Answer 1

这是一个简单的错误，我没有为监听器实例化“this”(实例)，而是使用了我之前定义但忘记删除的替代监听器。由于监听器是在 MainActivity 中实现的:

public class MainActivity extends AppCompatActivity implements AudioManager.OnAudioFocusChangeListener {

AM.requestAudioFocus(afChangeListener <-- should have been 'this',
                // Use the music stream.
                AudioManager.STREAM_MUSIC,
                // Request permanent focus.
                AudioManager.AUDIOFOCUS_GAIN);

requestAudioFocus() 声明不正确。

焦点更改的开关盒已正确编写:

@Override
    public void onAudioFocusChange(int focusChange) {
        switch (focusChange) {
            case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT:
                Toast.makeText(this, "FOCUS LOSS TRANSIENT", Toast.LENGTH_SHORT).show();
                pause();
                break;
            case AudioManager.AUDIOFOCUS_LOSS:
                pause();
                Toast.makeText(this, "FOCUS LOST", Toast.LENGTH_SHORT).show();
                break;
            case AudioManager.AUDIOFOCUS_GAIN_TRANSIENT:
                Intent i = new Intent("com.android.music.musicservicecommand");
                i.putExtra("command", "pause");
                MainActivity.this.sendBroadcast(i);
                AM.setStreamVolume(AudioManager.STREAM_MUSIC, AM.getStreamMaxVolume(AudioManager.STREAM_MUSIC), 0);
                play();
            case AudioManager.AUDIOFOCUS_REQUEST_FAILED:
                stop();
                break;
            case AudioManager.AUDIOFOCUS_REQUEST_GRANTED:
                Intent iARG = new Intent("com.android.music.musicservicecommand");
                iARG.putExtra("command", "pause");
                MainActivity.this.sendBroadcast(iARG);
                AM.setStreamVolume(AudioManager.STREAM_MUSIC, AM.getStreamMaxVolume(AudioManager.STREAM_MUSIC), 0);
                play();
                break;
        }
    }

在 MainActivity 的实现也正确编写:

public class MainActivity extends AppCompatActivity implements AudioManager.OnAudioFocusChangeListener