尝试在空对象上调用接口方法'android.media.session.ISession.getController()'

Question

以下代码是使用媒体会话（media session）构建音乐通知播放器及其控件的代码。每当我从通知中点击控件时，它就会崩溃，并出现上述错误。请查看下面的代码，并在我出错时进行更正。在下面的代码中，我使用了媒体会话和广播接收器来构建通知。"track" 是包含所有歌曲数据的模型类。

   try {
                if (track.getImage() == null) {
                    track.setImage(BitmapFactory.decodeResource(context.getResources(),
                            R.mipmap.ic_launcher));
                }
    
    
                NotificationManagerCompat notificationManagerCompat = NotificationManagerCompat.from(context);
                MediaSessionCompat mediaSessionCompat = new MediaSessionCompat(context, "tag");
                mediaSessionCompat.setMetadata(
                        new MediaMetadataCompat.Builder()
                                .putString(MediaMetadata.METADATA_KEY_TITLE, track.getTitle())
                                .putString(MediaMetadata.METADATA_KEY_ARTIST, track.getArtist())
                                .putBitmap(MediaMetadata.METADATA_KEY_ALBUM_ART, track.getImage())
                                .putString(MediaMetadata.METADATA_KEY_ALBUM, track.getAlbum())
                                .build()
                );
                mediaSessionCompat.setFlags(
                        MediaSessionCompat.FLAG_HANDLES_MEDIA_BUTTONS |
                                MediaSessionCompat.FLAG_HANDLES_TRANSPORT_CONTROLS);
    
                PlaybackStateCompat.Builder stateBuilder = new PlaybackStateCompat.Builder();
    
                stateBuilder.setActiveQueueItemId(MediaSession.QueueItem.UNKNOWN_ID);
    
                long actions = PlaybackStateCompat.ACTION_PLAY_PAUSE | PlaybackStateCompat.ACTION_STOP | PlaybackStateCompat.ACTION_SKIP_TO_NEXT | PlaybackStateCompat.ACTION_SKIP_TO_PREVIOUS;
                stateBuilder.setActions(actions);
                if (isPlaying) {
                    stateBuilder.setState(PlaybackStateCompat.STATE_PLAYING, 0, 1.0f);
                    mediaSessionCompat.setActive(true);
    
                } else {
                    stateBuilder.setState(PlaybackStateCompat.STATE_PAUSED, 0, 1.0f);
                    mediaSessionCompat.setActive(true);
    
    
                }
                mediaSessionCompat.setPlaybackState(stateBuilder.build());
                Bitmap icon = track.getImage();
    
    
                PendingIntent pendingIntentPrevious;
                int drw_previous;
    
    //                pendingIntentPrevious = null;
    //                drw_previous = 0;
                Intent intentPrevious = new Intent(context, NotificationActionService.class)
                        .setAction(ACTION_PREVIUOS);
                pendingIntentPrevious = PendingIntent.getBroadcast(context, 0,
                        intentPrevious, PendingIntent.FLAG_UPDATE_CURRENT);
                drw_previous = R.drawable.ic_back;
                Intent intentPlay = new Intent(context, NotificationActionService.class)
                        .setAction(ACTION_PLAY);
                PendingIntent pendingIntentPlay = PendingIntent.getBroadcast(context, 0,
                        intentPlay, PendingIntent.FLAG_UPDATE_CURRENT);
    
                PendingIntent pendingIntentNext;
                int drw_next;
    //                pendingIntentNext = null;
    //                drw_next = 0;
                Intent intentNext = new Intent(context, NotificationActionService.class)
                        .setAction(ACTION_NEXT);
                pendingIntentNext = PendingIntent.getBroadcast(context, 0,
                        intentNext, PendingIntent.FLAG_UPDATE_CURRENT);
                drw_next = R.drawable.ic_next;
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                    notification = new NotificationCompat.Builder(context, CHANNEL_ID)
                            .setSmallIcon(R.drawable.logo)
                            .setContentTitle(track.getTitle())
                            .setContentText(track.getArtist())
                            .setLargeIcon(icon)
                            .setAutoCancel(isPlaying ? false : true)
                            .setOngoing(isPlaying ? true : false)
                            .setWhen(0)
                            .setNotificationSilent()
                            .setSound(null)
                            .addAction(drw_previous, "Previous", pendingIntentPrevious)
                            .addAction(playbutton, "Play", pendingIntentPlay)
                            .addAction(drw_next, "Next", pendingIntentNext)
                            .setStyle(new androidx.media.app.NotificationCompat.MediaStyle()
                                    .setShowActionsInCompactView(0, 1, 2)
                                    .setMediaSession(mediaSessionCompat.getSessionToken()))
                            .setPriority(NotificationCompat.PRIORITY_LOW)
                            .build();
    
                } else {
                    notification = new NotificationCompat.Builder(context, CHANNEL_ID)
                            .setSmallIcon(R.drawable.logo)
                            .setContentTitle(track.getTitle())
                            .setContentText(track.getArtist())
                            .setLargeIcon(icon)
                            .setAutoCancel(true)
                            .setOngoing(false)
                            .setWhen(0)
                            .setNotificationSilent()
                            .setSound(null)
                            .addAction(drw_previous, "Previous", pendingIntentPrevious)
                            .addAction(playbutton, "Play", pendingIntentPlay)
                            .addAction(drw_next, "Next", pendingIntentNext)
                            .setStyle(new androidx.media.app.NotificationCompat.MediaStyle()
                                    .setShowActionsInCompactView(0, 1, 2)
                                    .setMediaSession(mediaSessionCompat.getSessionToken()))
                            .setPriority(NotificationCompat.PRIORITY_LOW)
                            .build();
    
                }
    
                notificationManagerCompat.notify(1, notification);
            } catch (Exception e) {
                Log.e("media sesison", e.getLocalizedMessage());
            }

   

- cutykaryspace

---

这个回答解决了你的问题吗？Android WebView 推送通知？ - frankenapps

@frankenapps 不是，我正在寻找具有播放暂停控件并通过应用内通知构建器处理的媒体播放通知。 - cutykaryspace

Answer 1

Android内部存在一个MediaSessions限制，SESSION_CREATION_LIMIT_PER_UID = 100;

您应该释放不再需要的MediaSession实例。

如何复现：

// Just create 100 instances of MediaSession
repeat(200) {
    val session = MediaSessionCompat(context, "Session") // Will cause a crash after 99 iterations
}

如何修复：

// You should release MediaSession instances that you don't need anymore.
repeat(200) {
    val session = MediaSessionCompat(context, "Session")
    session.release()
}

- Nikolay Krasilnikov

Answer 2

我遇到了同样的问题，我通过以下方法解决了它。

在创建会话时应调用setActive(true)，并在销毁时释放它。

- YUYI-CHEN