in Flutter, what is the difference between .addListener(nofityListeners) and .notifyListeners?-CodePudding

I am not even sure xxManager.notifyListeners() is valid because what I saw so far is just plain notifyListeners() being used in class that extend ChangeNotifier for example :

 Timer(
      const Duration(milliseconds: 2000),
      () {
        _initialized = true;
        notifyListeners();
      },
    );

here i tried to understand the meaning of

class AppRouter extends RouterDelegate<AppLink>
    with
        ChangeNotifier,
        PopNavigatorRouterDelegateMixin {
  @override
  final GlobalKey<NavigatorState> navigatorKey;

  final AppStateManager appStateManager;
  final XXManager xxManager;
  final YYManager yyManager;

  AppRouter({
    required this.appStateManager,
    required this.xxManager,
    required this.yyManager,
  })
      : navigatorKey = GlobalKey<NavigatorState>() {
    appStateManager.addListener(notifyListeners);       <-------This part
.
.
.
}

that part of the code for what I understand is to add listener to see the change in appStateManager which if changes will trigger notifyListeners method. what i dont understand is when i change it into:

appStateManager.notifyListeners();

it didnt show any error but when I ran it apparently it does not listen nor notify (the appStateManager has a Timer function which change the state in this case isInitialized to true after 2s so if the listener catch it, it will "route to next widget" (hope i said it correctly)). with 1st case it will change screen after 2s but on 2nd case it does nothin. what is wrong?

CodePudding user response：

It's pretty straight forward.
appStateManager.addListener() adds listeners.
appStateManager.notifyListeners() notifies those listeners.

But with this line:
appStateManager.addListener(notifyListeners);
You are adding listeners with the name notifyListeners. notifyListeners is a variable here. It's not the same as the method

CodePudding user response：

addListener is register a closure to be called when the object changes.

notifyListeners is Calling all the registered listeners.

Note that:

with addListener, if you want to add an instance, then it must be removed the same number of times it is added before it will stop being called.
these methods must not be called after dispose has been called.