Is it possible to share and update one screen's reactive value in another screen without Provid-CodePudding

So I have this block of code in a widget that navigates to another screen:

screen_one.dart

class ScreenOne extends StatefulWidget {
  const ScreenOne({ super.key });

  @override
  State<ScreenOne> createState() => _ScreenOneState();
}

class _ScreenOneState extends State<ScreenOne> {
  List<String> state = [''];

  @override
  Widget build(BuildContext context) {
    return Column(
      MaterialButton(
        onPressed: () => Navigator.pushNamed(context, '/screen-two'),
        child: Text('Click here.')
      ),
      Text(state[0]),
    );
  }
}

screen_two.dart

class ScreenTwo extends StatelessWidget {
  const ScreenTwo({ super.key });

  @override
  Widget build(BuildContext context) {
    return Container();
  }
}

Basically I need to pass the state variable from ScreenOne to ScreenTwo and then update it there (in ScreenTwo)

ScreenTwo needs to display the same thing as ScreenOne and add() a new item to the state list when some button is clicked which should show on both the screens.

Its just one simple List so I am trying to avoid using provider.

Is it possible to do though?

I'm currently just passing it through the Navigator:

screen_one.dart

Navigator.pushNamed(
  context,
  '/post-info',
  arguments: state,
),

screen_two.dart

Widget build(BuildContext context) {
  final List<String> post = ModalRoute.of(context)!.settings.arguments as List<String>;
  // ...
}

CodePudding user response：

first I want to recommend you when things go bigger and more complex, it's better to use a state management approach, However since you did say that you have only one List you can simply use a ValueNotifier, with ValueListenableBuilder: // this should be outside widget classes, maybe in a custom-made class or just in a global scope. ValueNotifier stateNotifier = ValueNotifier([""]);

now in the places you want to use that state, you can use ValueListenableWidget like this:

  ValueListenableBuilder(
      valueListenable: stateNotifier,
      builder: (context, value, child) {
        return Column(
          children: [
            Text('${state[0]}'),
            MaterialButton(
              onPressed: () {
               Navigator.pushNamed(context, '/screen-two'),
              },
              child: Text('click'),
            ),
          ],
        );
      },
    );
  }
}

and any other place where you want to see that state get updates, you need to use ValueListenableWidget.

Now, for executing a method like add() on the List and notify the widgets, you need to assign a new value for it like this:

void addInTheList(String elem) {
   List current = stateNotifier.value;
   current.add(elem);
   
   // this exactly what will be responsible for updating.
   stateNotifier.value = current;
 }

now, you can just call addInTheList and expect it to update in all of them:

addInTheList("Example");