onBackgroundMessageReceived method
Handles push notification received when app is background. Since FCM itself displays the notification when app is background, this method makes it easier to determine whether the notification should be displayed or not.
@see onMessageReceived for more details
Implementation
Future<bool> onBackgroundMessageReceived(Map<String, dynamic> message) =>
onMessageReceived(message,
handleNotificationTrigger: message['notification'] == null);