FState

FState.dart

import 'package:flutter/material.dart';

class FState<T extends Widget> extends StatefulWidget {
  final T scoped;
  final Widget Function(T widget, void Function(VoidCallback)) Function()
      builder;

  const FState(this.scoped, this.builder, {super.key});

  @override
  FStateState<T> createState() => FStateState<T>();
}

class FStateState<T extends Widget> extends State<FState<T>> {
  late final _builder = widget.builder();

  @override
  build(context) {
    return _builder(widget.scoped, setState);
  }
}

main.dart

import 'package:example/fstate.dart';
import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

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

  @override
  createState() => MyAppState();
}

class MyAppState extends State<MyApp> {
  String _title = 'Flutter Demo Home Page';

  void updateTitle(String title) {
    setState(() {
      _title = title;
    });
  }

  @override
  build(context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: MyHomePage(
        title: _title,
        updateTitle: updateTitle,
      ),
    );
  }
}

class MyHomePage extends StatelessWidget {
  final String title;
  final void Function(String title) updateTitle;

  const MyHomePage({
    super.key,
    required this.title,
    required this.updateTitle,
  });

  @override
  build(context) {
    return FState<MyHomePage>(
      this,
      () {
        int counter = 0;
        final controller = TextEditingController();

        controller.addListener(
          () {
            updateTitle(controller.text);
          },
        );

        return (widget, setState) {
          return Scaffold(
            appBar: AppBar(
              backgroundColor: Theme.of(context).colorScheme.inversePrimary,
              title: Text(widget.title),
            ),
            body: Center(
              child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                  const Text('You have pushed the button this many times:'),
                  TextField(controller: controller),
                  Text(
                    '$counter',
                    style: Theme.of(context).textTheme.headlineMedium,
                  ),
                ],
              ),
            ),
            floatingActionButton: FloatingActionButton(
              onPressed: () {
                setState(() {
                  counter++;
                });
              },
              tooltip: 'Increment',
              child: const Icon(Icons.add),
            ),
          );
        };
      },
    );
  }
}