onMessageOpenedApp property
Returns a Stream that is called when a user presses a notification displayed via FCM.
A Stream event will be sent if the app has opened from a background state (not terminated).
If your app is opened via a notification whilst the app is terminated, see getInitialMessage.
Implementation
// ignore: close_sinks, never closed
static final StreamController<RemoteMessage> onMessageOpenedApp =
StreamController<RemoteMessage>.broadcast();