问Android Audio Focus Listener在服务中不工作

EN

import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.media.AudioAttributes;
import android.media.AudioFocusRequest;
import android.media.AudioManager;
import android.media.ToneGenerator;
import android.os.Build;
import android.os.Handler;
import android.os.IBinder;
import android.os.Looper;
import android.util.Log;

public class PlayToneService extends Service implements AudioManager.OnAudioFocusChangeListener {
    private static final String TAG = "PlayToneService";

    public PlayToneService() {
    }

    @Override
    public void onCreate() {
        super.onCreate();

        AudioManager audioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);

        Log.d(TAG,"AudioManager.requestAudioFocus...");
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            audioManager.requestAudioFocus(new AudioFocusRequest.Builder(AudioManager.AUDIOFOCUS_GAIN)
                    .setAudioAttributes(
                            new AudioAttributes.Builder()
                                    .setUsage(AudioAttributes.USAGE_MEDIA)
                                    .setContentType(AudioAttributes.CONTENT_TYPE_MUSIC)
                                    .build()
                    )
                    .setAcceptsDelayedFocusGain(true)
                    .setOnAudioFocusChangeListener(this).build()
            );
        } else {

            audioManager.requestAudioFocus(this,
                    AudioManager.STREAM_MUSIC,
                    AudioManager.AUDIOFOCUS_GAIN);
        }



    }

    @Override
    public IBinder onBind(Intent intent) {
        // TODO: Return the communication channel to the service.
        throw new UnsupportedOperationException("Not yet implemented");
    }

    @Override
    public void onAudioFocusChange(int focusChange) {
        if (focusChange == AudioManager.AUDIOFOCUS_GAIN) {
            // You now have the audio focus and may play sound.
            final ToneGenerator tg = new ToneGenerator(AudioManager.STREAM_NOTIFICATION, 500);
            tg.startTone(ToneGenerator.TONE_PROP_BEEP);
            Log.d(TAG,"AudioManager.AUDIOFOCUS_REQUEST_Sucess...");

            new Handler(Looper.getMainLooper()).postDelayed(new Runnable() {
                public void run() {
                    tg.release();
                    stopSelf();
                }
            },550);
        }
        else if (focusChange == AudioManager.AUDIOFOCUS_REQUEST_FAILED) {
            // Handle the failure.
            Log.d(TAG,"AudioManager.AUDIOFOCUS_REQUEST_FAILED ...");
            stopSelf();

        }

    }
}