When to show local authentication screen (with device biometric or passcode)

Question

In my application, I want to show the user local auth screen to identify itself after closing or putting the application in inactive mode. Possible AppLifecycleState are:

enum AppLifecycleState {
detached,
resumed,
inactive,
hidden,
pause,
}

I've used local_auth package and with WidgetBindingObserver to listen to app states. Now I have a method that returns a boolean to whether to show the local_auth screen or not.

 Future<bool> get shouldShowLocalAuthenticationScreen async {
    bool result = false;
    // whit scan method you can get the intermediate result
    final subscription = _appLifeCycleStateSubject
        .scan<List<ui.AppLifecycleState>>(
            (list, value, _) => [...list, value], []).listen((list) {
      if (list.last == ui.AppLifecycleState.resumed && list.length > 1) {
        // So if the last state is AppLifecycleState.resumed and list have
        // more than one element then the application should show LocalAuthScreen.

        // Some possible combination where the last state is AppLifecycleState.resumed.
        //[AppLifecycleState.inactive, AppLifecycleState.resumed]

        // [AppLifecycleState.paused, AppLifecycleState.hidden,
        //AppLifecycleState.inactive, AppLifecycleState.resumed]

        //[AppLifecycleState.inactive, AppLifecycleState.hidden,
        //AppLifecycleState.paused, AppLifecycleState.hidden,
        //AppLifecycleState.inactive, AppLifecycleState.resumed]
        result = true;
      }
    });
    subscription.cancel();
    return result;
  }

I have 2 questions, The first one is did I consider all the possible changes in the state and is the app secure due it shows sensitive information? The second one is should I call subscription.cancel(); even though subscription is inside the getter.