当 Oreo 中的服务被销毁时，防止通知被驳回

好的。我有一个关于在 Android Oreo 中保留媒体播放器服务的问题。基于这里的讨论：

Android Oreo：保持已启动的后台服务处于活动状态而不将其设置为前台（但有通知）？

在 Android Oreo 中处理媒体播放器服务的正确方法似乎是在媒体播放器暂停时存储状态信息，因此如果媒体播放器被破坏，按“播放”将创建一个新的媒体播放器并从停止的地方开始。

我的问题是如何创建一个通知，当启动它的服务被销毁时，该通知不会被销毁。我没有运行任何代码来消除通知，但当服务被销毁时，它仍然会自动消除。正如您在我的代码中看到的，我可以重建 onDestroy 通知，但我不喜欢它的外观，因为用户可以看到它被关闭并再次重建。

这是我的通知代码：

private void buildNotification() {
        Cat.d("building notification");
        final MediaPlayerService context = this;

        RequestBuilder<Bitmap> requestBuilder = Glide.with(this).asBitmap()
                .load(R.mipmap.ic_launcher);

        NotificationCompat.Action action;
        if (mediaPlayer != null && mediaPlayer.isPlaying())
            action = generateAction(R.drawable.ic_pause, "Pause");
        else
            action = generateAction(R.drawable.ic_play_arrow, "Play");

        int[] actionsInCompact;

        builder = new NotificationCompat.Builder(context, NOTIFICATION_CHANNEL_ID)
                .setSmallIcon(R.drawable.ic_navbooks_icon_black)
                //.setOnlyAlertOnce(true)
                .setContentTitle(book.getTitle())
                .setContentText(book.getAuthor())
                .setAutoCancel(false)
                .setContentIntent(PendingIntentHelper.getOpenMainActivityIntent(context, book.getId()))
                .setDeleteIntent(PendingIntentHelper.getStopServiceIntent(context));

        if (SettingsUtil.GetNotificationSkip(context)) {
            builder.addAction(R.drawable.ic_skip_backward, "Skip Previous",
                    PendingIntentHelper.getSkipBackwardIntent(context))
                    .addAction(R.drawable.ic_backward, "Rewind",
                            PendingIntentHelper.getSeekBackwardIntent(context))
                    .addAction(action)
                    .addAction(R.drawable.ic_forward, "Fast Forward",
                            PendingIntentHelper.getSeekForwardIntent(context))
                    .addAction(R.drawable.ic_skip_forward, "Skip Next",
                            PendingIntentHelper.getSkipForwardIntent(context));
            actionsInCompact = new int[]{0, 1, 2, 3, 4};
        } else {
            builder.addAction(R.drawable.ic_backward, "Rewind",
                    PendingIntentHelper.getSeekBackwardIntent(context))
                    .addAction(action)
                    .addAction(R.drawable.ic_forward, "Fast Forward",
                            PendingIntentHelper.getSeekForwardIntent(context));
            actionsInCompact = new int[]{0, 1, 2};
        }
        builder.setStyle(new android.support.v4.media.app.NotificationCompat.MediaStyle()
                .setMediaSession(mediaSession.getSessionToken())
                .setShowActionsInCompactView(actionsInCompact));

        // Load a cover image if there isn't one loaded yet or the cover has changed
        if(cover == null || !book.getCover().equals(lastCover)) {
            lastCover = book.getCover();
            mediaSession.setMetadata(new MediaMetadataCompat.Builder()
                    .putString(MediaMetadataCompat.METADATA_KEY_ARTIST, book.getTitle())
                    .putString(MediaMetadataCompat.METADATA_KEY_TITLE, book.getAuthor())
                    .build());
            Glide.with(this)
                    .asBitmap()
                    .error(requestBuilder)
                    .load(book.getCover())
                    .into(new SimpleTarget<Bitmap>() {
                        @Override
                        public void onResourceReady(Bitmap largeIcon, Transition transition) {
                            Cat.d("Finished loading");
                            cover = largeIcon;
                            // initBuilder
                            builder.setLargeIcon(largeIcon);
                            mediaSession.setMetadata(new MediaMetadataCompat.Builder()
                                    .putBitmap(MediaMetadataCompat.METADATA_KEY_ALBUM_ART, largeIcon)
                                    .putString(MediaMetadataCompat.METADATA_KEY_ARTIST, book.getTitle())
                                    .putString(MediaMetadataCompat.METADATA_KEY_TITLE, book.getAuthor())
                                    .build());
                            startNotification();
                        }
                    });
        } else {
            mediaSession.setMetadata(new MediaMetadataCompat.Builder()
                    .putBitmap(MediaMetadataCompat.METADATA_KEY_ALBUM_ART, cover)
                    .putString(MediaMetadataCompat.METADATA_KEY_ARTIST, book.getTitle())
                    .putString(MediaMetadataCompat.METADATA_KEY_TITLE, book.getAuthor())
                    .build());
            if(cover != null)
                builder.setLargeIcon(cover);
        }

        startNotification();
    }

    private NotificationCompat.Action generateAction(int icon, String title) {
        return new NotificationCompat.Action.Builder( icon, title, PendingIntentHelper.getPlayPauseIntent(this)).build();
    }

    private void startNotification() {
        mediaSession.setPlaybackState(new PlaybackStateCompat.Builder()
                .setActions(MEDIA_SESSION_ACTIONS)
                .setState(mediaPlayer.isPlaying() ? PlaybackStateCompat.STATE_PLAYING :
                        PlaybackStateCompat.STATE_PAUSED, book.getLastPosition(), 1)
                .build());

        if(mediaPlayer.isPlaying())
            startForeground(NOTIFICATION_ID, builder.build());
        else
        {
            NotificationManager notificationManager =
                    (NotificationManager)getSystemService(NOTIFICATION_SERVICE);
            if(notificationManager != null) {
                notificationManager.notify(NOTIFICATION_ID, builder.build());
            }
            stopForeground(false);
        }
    }

以下是服务被销毁时会发生的情况：

@Override
public void onDestroy() {
    //super.onDestroy();
    handleDestroy();
}

private void handleDestroy() {
        if(book != null)
            sendProgressUpdate();
        else
            book = new BookDBHelper(this).getBook(SettingsUtil.GetLastPlayedBook(this));
        if(mediaPlayer != null) {
            book.setLastPosition(this, getPosition());
            SyncHelper.SendProgressUpdate(this, book);
        }
        if(mediaSession != null)
            mediaSession.release();

        if(noisyRegistered) {
            unregisterReceiver(becomingNoisyReceiver);
            unregisterReceiver(shakeReceiver);
        }
        buildNotification();
    }

好的。我发现 stopForeground 函数有一个可选参数，即标志而不是布尔值。可以给它一个标志 STOP_FOREGROUND_DETACH ，即使在调用 stopForeground 之后，该标志也是从服务中分离通知所必需的，这样当服务被销毁时，通知不会被消除，并且不必构建新的通知。这是我用于启动通知的更新代码：

private fun updateNotification(preparing: Boolean = false) {
    if(getPlaying()) { 
        startService(Intent(applicationContext, [email protected]))
        startForeground(NOTIFICATION_ID, getNotification())
    }else {
        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.N)
            stopForeground(Service.STOP_FOREGROUND_DETACH)
        else
            stopForeground(false)
        notificationManager.notify(NOTIFICATION_ID, getNotification())
    }
}