A background message could not be handled in dart as no onbackgroundmessage handler has been registered.

Background Message Handling in Dart

In Dart, background messages cannot be handled if no onBackgroundMessage handler has been registered. The
onBackgroundMessage handler is essential for handling messages received while the application is in the
background or terminated state.

Example

Let’s assume you are using the Flutter framework with Dart language and you want to handle background messages in your
app. To enable background message handling, you need to follow these steps:

1. Add Dependencies: First, make sure you have the required dependencies in your pubspec.yaml
   file.

   dependencies:
     firebase_messaging: ^x.x.x  # Replace with the latest version
               

2. Register Callback: In your main.dart file, inside the main() function,
   register the onBackgroundMessage() handler before calling runApp().

   import 'package:firebase_messaging/firebase_messaging.dart';
   
   Future backgroundHandler(RemoteMessage message) async {
     print("Handling a background message: ${message.messageId}");
     // Perform your custom handling logic here
   }
   
   void main() {
     FirebaseMessaging.onBackgroundMessage(backgroundHandler);
     runApp(MyApp());
   }
               

3. Handle Incoming Messages: Implement the backgroundHandler() function according to your
   application’s requirements. This function will be called whenever a background message is received.
4. Test Background Messaging: Test the background messaging functionality by sending a background message
   to your application. You can use tools like Firebase Cloud Messaging (FCM) or third-party libraries to send background
   messages to your app. Make sure your app is registered with relevant messaging services (e.g., FCM) and has the necessary
   configurations.

By following these steps, you can enable Dart background message handling in your application. The onBackgroundMessage
handler allows you to implement custom logic for processing incoming messages when the app is not active or running in
the background.