How should you properly handle a push notification differently depending on whether your app is currently genuinely running in the foreground, running in the background, or completely fully terminated?

Firebase Cloud Messaging genuinely provides several genuinely separate distinct callback handlers depending on your app's own current specific state, with onMessage properly handling a notification received while the app is genuinely currently actively running in the foreground, letting you display your own genuinely custom in app notification banner instead of relying on the operating system's own default one, onMessageOpenedApp properly handling the case where a user actually taps a notification that had brought the app back from a background state, and a separate top level background message handler properly handling messages received while the app is genuinely completely terminated.

FirebaseMessaging.onMessage.listen((RemoteMessage message) {
  showInAppBanner(message.notification?.title);
});

FirebaseMessaging.onMessageOpenedApp.listen((message) {
  navigateToRelevantScreen(message.data);
});