Firebase扩展通知在应用程序处于后台时显示图像

我正在Android中实现FCM通知，但是通知根据应用程序状态(后台还是前台)有何不同?

I am implementing FCM notifications in Android, but how does notifications differ depending on the app status (background vs. foreground)?

我正在使用带有Postman的FCM API发送通知，这是通知结构:

I am sending the notification using the FCM API with Postman and this is the notification structure:

{ "notification": {
      "title": "Notification title",
      "body": "Notification message",
      "sound": "default",
      "color": "#53c4bc",
      "click_action": "MY_BOOK",
      "icon": "ic_launcher"
   },
   "data": {
       "main_picture": "URL_OF_THE_IMAGE"  
   },
   "to" : "USER_FCM_TOKEN"
}

要渲染的图像是从data.main_picture拍摄的.

The image to render is taken from data.main_picture.

我已经实现了自己的FirebaseMessagingService，它使通知在前台状态下完美显示.通知代码是下一个:

I have implemented my own FirebaseMessagingService which makes the notifications display perfectly in foreground state. The notification code is the next:

NotificationCompat.BigPictureStyle notiStyle = new NotificationCompat.BigPictureStyle();
notiStyle.setSummaryText(messageBody);
notiStyle.bigPicture(picture);

Uri defaultSoundUri= RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);

NotificationCompat.Builder notificationBuilder = (NotificationCompat.Builder) new NotificationCompat.Builder(this)
            .setSmallIcon(R.drawable.ic_launcher)
            .setLargeIcon(bigIcon)
            .setContentTitle(title)
            .setContentText(messageBody)
            .setAutoCancel(true)
            .setSound(defaultSoundUri)
            .setContentIntent(pendingIntent)
            .setStyle(notiStyle); code here

NotificationManager notificationManager =
            (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
notificationManager.notify(0, notificationBuilder.build());

但是，在后台，该服务甚至没有执行.在AndroidManifest.xml中，Firebase服务声明如下:

However, in background, the service is not even executed. In the AndroidManifest.xml, Firebase services are declared as follow:

<service
    android:name=".MyFirebaseMessagingService">
  <intent-filter>
    <action android:name="com.google.firebase.MESSAGING_EVENT"/>
  </intent-filter>
</service>

<service
    android:name=".MyFirebaseInstanceIDService">
  <intent-filter>
    <action android:name="com.google.firebase.INSTANCE_ID_EVENT"/>
  </intent-filter>
</service>

我的问题不是LargeIcon或SmallIcon，而是显示大图.

My problem is not the LargeIcon or SmallIcon but displaying the big picture.

感谢您的支持.