Flutter ScrollController AssertionError: '_positions.isNotEmpty': ScrollController not attached to any scroll views when closing route

Question

I'm encountering an error in my Flutter application related to a ScrollController. I have a QuestionDetailsScreen where I'm using a ScrollController to monitor the scroll position. I want to trigger a function in my controller fireWhenCloseQuestionDetails() when the QuestionDetailsScreen route is closed. To do this, I've implemented a custom NavigatorObserver. However, I'm getting an error:

'_positions.isNotEmpty': ScrollController not attached to any scroll views

Here's my QuestionBankController:

  class QuestionBankController extends GetxController {
  ScrollController questionDetailsScrollCtrl = ScrollController();

  @override
  void onInit() {
    questionDetailsScrollCtrl = ScrollController();
    questionDetailsScrollCtrl.addListener(_onScroll);
    super.onInit();
  }

  void _onScroll() {
    // This function will be called every time the scroll position changes
    print("Scroll position: ${questionDetailsScrollCtrl.position.pixels}");
  }

  void fireWhenCloseQuestionDetails() {
    print("Fire");
    print(questionDetailsScrollCtrl.position.pixels);
  }

  @override
  void onClose() {
    print("On close");
    questionDetailsScrollCtrl.dispose();
    super.onClose();
  }
}

I'm using a custom NavigatorObserver to trigger fireWhenCloseQuestionDetails() when the QuestionDetailsScreen route is closed:

class MyNavigatorObserver extends NavigatorObserver {
  @override
  void didPop(Route<dynamic> route, Route<dynamic>? previousRoute) {
    if (route.settings.name == "/questiondetailsscreen") {
      Future.delayed(Duration.zero, () {
        QuestionBankController().fireWhenCloseQuestionDetails();
      });
    }
  }
}

It seems like the issue might be related to creating a new instance of QuestionBankController when calling fireWhenCloseQuestionDetails(). How can I ensure I'm using the correct instance of QuestionBankController associated with my QuestionDetailsScreen specifically when closing the route?

Additional Information:

• The scroll listening functionality is working correctly while scrolling.

Answer 1

How about calling fireWhenCloseQuestionDetails() in QuestionBankController's onClose?

@override
void onClose() {
  print("On close");
  fireWhenCloseQuestionDetails();
  questionDetailsScrollCtrl.dispose();
  super.onClose();
}

Probably if your QuestionBankController is bound to QuestionDetailsScreen.