MediaPlayer - setAudioAttributes not working properly

问题

I'm trying to create an alarm, everything is working fine but the stream type is always media even tho I use STREAM_ALARM, since setStreamType is deprecated, I'm using setAudioAttributes instead but it doesn't seem to work. here's my code :

class AlarmRingtoneManager(val context: Context) {

    private lateinit var mediaPlayer: MediaPlayer

    fun start() {
        mediaPlayer = MediaPlayer.create(context,  RingtoneManager.getDefaultUri(RingtoneManager.TYPE_ALARM))
           .apply {
              setAudioAttributes(AudioAttributes.Builder()
                .setFlags(AudioAttributes.FLAG_AUDIBILITY_ENFORCED)
                .setLegacyStreamType(AudioManager.STREAM_ALARM)
                .setUsage(AudioAttributes.USAGE_ALARM)
                .setContentType(AudioAttributes.CONTENT_TYPE_SONIFICATION)
                .build())
              isLooping = true
              start()
           }
    }

    fun stop() {
      mediaPlayer.stop()
    }
}

回答1:

The problem is that you are creating the MediaPlayer using the method MediaPlayer.create(), and it is not possible to change the AudioAttributes later if you do it like that.

From the documentation:

Convenience method to create a MediaPlayer for a given resource id. On success, prepare() will already have been called and must not be called again.

When done with the MediaPlayer, you should call release(), to free the resources. If not released, too many MediaPlayer instances will result in an exception.

Note that since prepare() is called automatically in this method, you cannot change the audio session ID (see setAudioSessionId(int)) or audio attributes (see setAudioAttributes(android.media.AudioAttributes) of the new MediaPlayer.

Instead of using create(), just instantiate the MediaPlayer using the default constructor new MediaPlayer();. Then, set the source with the method setDataSource() and set the rest of the AudioAttributes as you were doing before.

I don't know about Kotlin, but in Java it would look something like this:

MediaPlayer mediaPlayer = new MediaPlayer();
mediaPlayer.setAudioAttributes(AudioAttributes.Builder()
                .setFlags(AudioAttributes.FLAG_AUDIBILITY_ENFORCED)
                .setLegacyStreamType(AudioManager.STREAM_ALARM)
                .setUsage(AudioAttributes.USAGE_ALARM)
                .setContentType(AudioAttributes.CONTENT_TYPE_SONIFICATION)
                .build());
mediaPlayer.setDataSource(context, RingtoneManager.getDefaultUri(RingtoneManager.TYPE_ALARM));
mediaPlayer.setLooping(true);
mediaPlayer.prepare();
mediaPlayer.start();

来源：https://stackoverflow.com/questions/56210872/mediaplayer-setaudioattributes-not-working-properly