onMessage

Catch foreground notifications with onMessage.

The onMessage stream

The onMessage stream catches notifications that arrive while the app is in the foreground. This stream returns a Stream<RemoteMessage> and is listened to with listen. It is used to show a snackbar or dialog when a notification arrives in foreground.

messaging.onMessage.listen((message) {
  print(message.title);
});

The RemoteMessage class

RemoteMessage is the class that holds the data of an incoming notification. You access the notification content through its title, body, and data fields. The data field carries custom key-value pairs.

messaging.onMessage.listen((message) {
  print(message.data['key']);
});

Exercise Listen to the onMessage stream

Get the messaging instance, listen to the onMessage stream with listen and print message.title. Wait 10 milliseconds after starting to listen.

Show example solution

class RemoteMessage {
  final String title;
  RemoteMessage(this.title);
}

class FirebaseMessaging {
  static final FirebaseMessaging instance = FirebaseMessaging._();
  FirebaseMessaging._();
  Stream<RemoteMessage> get onMessage => Stream.value(RemoteMessage('Merhaba'));
}

void main() async {
  FirebaseMessaging.instance.onMessage.listen((message) {
    print(message.title);
  });
  await Future.delayed(Duration(milliseconds: 10));
}

Test yourself

When does the onMessage stream emit an event?
- When the device boots
- When a notification arrives while the app is in foreground
- Only during initialization
- Only when the app is closed
Show answer

When a notification arrives while the app is in foreground — onMessage emits only when a notification arrives while the app is in foreground; it does not fire in background or when closed.

Listen to onMessage

FirebaseMessaging.instance.____.listen((message) {
  print(message.title);
});

Show answer

FirebaseMessaging.instance.onMessage.listen((message) {
  print(message.title);
});

onMessage parts

onMessage

Foreground stream
RemoteMessage

Notification data
listen

Listens to the stream
foreground

App in foreground

Next lesson: onBackgroundMessage

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