What does appStateManager.addListener(notifyListeners); mean?-CodePudding

I am following raywenderlich's flutter apprentice tutorial (Chapter 7 https://www.raywenderlich.com/books/flutter-apprentice/v1.0/chapters/7-routes-navigation) and I am not able to understand what the call to addListener(notifyListener) means in the following code. Specifically, I am thinking that addListener should be taking in a Listener object but here, it is taking a function which is defined in the super class!

class AppRouter extends RouterDelegate
    with ChangeNotifier, PopNavigatorRouterDelegateMixin {
 
  // 3
  final AppStateManager appStateManager;
  // 4
  final GroceryManager groceryManager;
  final ProfileManager profileManager;

  AppRouter({
    required this.appStateManager,
    required this.groceryManager,
    required this.profileManager,
  }) : navigatorKey = GlobalKey<NavigatorState>() {
    appStateManager.addListener(notifyListeners); 
    groceryManager.addListener(notifyListeners);
    profileManager.addListener(notifyListeners);
  }
...
}

Any idea what is going on and how it is working?

CodePudding user response：

Essentially, the addListener functions adds a listener, that triggers the functions that's provided. So essentially, every time the XXXStateManager state changes, it will trigger the notifyListeners method from the ChangeNotifier class