在Android 13中，通知的下一页和上一页按钮已被隐藏。要显示这些按钮，需要添加以下代码：

if(Build.VERSION.SDK_INT>=Build.VERSION_CODES.S){
      Notification.BubbleMetadata bubbleMetadata = null;
      Notification.Builder builder = new Notification.Builder(context, channelId)
                  .setContentTitle(title)
                  .setContentText(content)
                  .setSmallIcon(R.drawable.ic_launcher_foreground)
                  .setBubbleMetadata(bubbleMetadata);

      Notification.Action prevAction = new Notification.Action.Builder(
          Icon.createWithResource(context, R.drawable.ic_previous),
          "Previous",
          prevPendingIntent
      ).build();

      Notification.Action nextAction = new Notification.Action.Builder(
          Icon.createWithResource(context, R.drawable.ic_next),
          "Next",
          nextPendingIntent
      ).build();

      builder.addAction(prevAction);
      builder.addAction(nextAction);

      notificationManager.notify(notificationId, builder.build());
  }
  else {
      NotificationCompat.Builder builder = new NotificationCompat.Builder(context, channelId)
                  .setContentTitle(title)
                  .setContentText(content)
                  .setSmallIcon(R.drawable.ic_launcher_foreground);

      NotificationCompat.Action prevAction = new NotificationCompat.Action.Builder(
          R.drawable.ic_previous,
          "Previous",
          prevPendingIntent
      ).build();

      NotificationCompat.Action nextAction = new NotificationCompat.Action.Builder(
          R.drawable.ic_next,
          "Next",
          nextPendingIntent
      ).build();

      builder.addAction(prevAction);
      builder.addAction(nextAction);

      notificationManager.notify(notificationId, builder.build());
  }

上面的代码进行了检查，如果设备API级别为Android 13或更高级别，则使用Notification.BubbleMetadata和Notification.Action.Builder添加下一页和上一页按钮。否则，使用NotificationCompat.Action.Builder添加按钮。

值得注意的是，添加下一页和上一页按钮将使通知显示为气泡。如果您不想要气泡，可以将Notification.BubbleMetadata和setBubbleMetadata()删除，并将builder替换为NotificationCompat.Builder。