Why is onTokenRefresh not firing? - flutter

Question

I'm new to firebase messaging and flutter. According to the flutter firebase_messaging package docs, onTokenRefresh is fired when a new FCM token is generated. And according to Google's firebase docs there are two scenarios that triggers token generation:
When a new token is generated on initial app startup
Whenever an existing token is changed
Here is a simplified version of the main function of my application. After each execution, I delete the app from the emulator and the displayed token does indeed change. Despite this, onTokenRefresh is never fired and it should if my understanding of the documentation is correct.
Future<void> main() async {
WidgetsFlutterBinding.ensureInitialized();
await Firebase.initializeApp();
FirebaseMessaging.instance.onTokenRefresh.listen((String token) {
print("New token: $token");
});
String token = await FirebaseMessaging.instance.getToken();
print("Token: $token");
//runApp(MyApp());
}
As I said, I'm new to flutter, dart and firebase messaging, is there something I'm fundamentally misunderstanding? Thanks.

Answer 1

So I think I figured it out. I noticed that sometimes, the onTokenRefresh does indeed fire. And I was wondering if it had something to do with how the flutter application is launched onto the emulator, in the sense that there is a race condition between when the token is generated and the listener attached.
To get the app to appear to start for the first time, I wiped the app data. Unfortunately this causes the flutter to automatically disconnect from the app which means I won't see the output of the print statement. So instead of trying to print when the token generation occurs, I assigned a value from the onTokenRefresh listener to a variable. I then updated a text widget with the value of the variable. And onTokenRefresh does indeed fire each time at start up if the app data has previously been wiped.