Flutter Updating Widget State

Issue

I have stateful widget class and it's state class. I have gridview widget in state class and list of widgets -in state class- belongs to gridview children. I want to update state when i changed my list of widgets because if i don't ui doesn't changes. How can i do that or what is the correct way?

class UIHandler extends StatefulWidget {

  const UIHandler({ Key? key}) : super(key: key);

  static List<Widget> widgets = [];

  void someFunc() { /* Do some changes on widgets list but that doens't changes ui so i want to update state */}

..
}

class _UIHandlerState extends State<UIHandler> { 

  
  @override
  Widget build(BuildContext context) {
     return GridView.count(
        children: List.of(UIHandler.widgets),
      );
  }
}

Solution

Ideally, there should not be any logic in StatefulWidget. The list of widgets should be maintained outside the stateful widget and passed via the constructor. The UI is automatically rebuilt when the list of widgets passed changes.

However to access the state within the widget use a global key for the widget. The current state can be accessed using it.

class UIHandler extends StatefulWidget {
  // create a global key
  static final _uiHandlerKey = GlobalKey<_UIHandlerState>();

  // use the global key here
  UIHandler() : super(key: _uiHandlerKey);

  static List<Widget> widgets = [];

  void someFunc() {
    // access the current state of the widget
    final state = _uiHandlerKey.currentState;
    if (state != null) {
      state.callSetState();
    }
  }
}

class _UIHandlerState extends State<UIHandler> { 
  // because setState is protected
  void callSetState() {
    setState(() {});
  }
  
  @override
  Widget build(BuildContext context) {
     return GridView.count(
        children: List.of(UIHandler.widgets),
     );
  }
}

Since we are using the same GlobalKey for all instances of UIHandler, there can only be one UIHandler at any time.

Answered By - Navaneeth P