Future controller idea

future.dart

import 'package:flutter/material.dart';

typedef FutureGenerator<T> = Future<T> Function();

class FutureController<T> {
  Future<T>? _future;
  VoidCallback? _onUpdate;
  final FutureGenerator<T>? _futureGenerator;

  FutureController({FutureGenerator<T>? futureGenerator})
      : _futureGenerator = futureGenerator {
    // Generate the initial future if a generator is provided
    if (_futureGenerator != null) {
      _future = _futureGenerator();
    }
  }

  Future<T>? get future => _future;

  void refresh() {
    if (_futureGenerator != null) {
      _future = _futureGenerator();
      _notifyListeners();
    }
  }

  void _notifyListeners() {
    _onUpdate?.call();
  }

  void addListener(VoidCallback onUpdate) {
    _onUpdate = onUpdate;
    // If the future is not set, generate and notify listeners immediately.
    if (_future == null && _futureGenerator != null) {
      _future = _futureGenerator();
      _notifyListeners();
    }
  }
}

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

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: MyFutureBuilderWidget(),
    );
  }
}

class MyFutureBuilderWidget extends StatefulWidget {
  @override
  _MyFutureBuilderWidgetState createState() => _MyFutureBuilderWidgetState();
}

class _MyFutureBuilderWidgetState extends State<MyFutureBuilderWidget> {
  late FutureController<String> futureController;

  @override
  void initState() {
    super.initState();
    futureController = FutureController<String>(
      futureGenerator: fetchData, // Provide the future generator
    );

    // Add listener to rebuild when future updates
    futureController.addListener(() {
      setState(() {});
    });
  }

  Future<String> fetchData() async {
    await Future.delayed(Duration(seconds: 5));
    return 'Data Loaded';
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('FutureController with FutureBuilder')),
      body: FutureBuilder<String>(
        future: futureController.future,
        builder: (context, snapshot) {
          if (snapshot.connectionState == ConnectionState.waiting) {
            return Center(child: CircularProgressIndicator());
          }
          if (snapshot.hasError) {
            return Center(child: Text('Error: ${snapshot.error}'));
          }
          return Center(child: Text(snapshot.data ?? 'No data'));
        },
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () => futureController.refresh(),
        child: Icon(Icons.refresh),
      ),
    );
  }
}

Using a ValueNotifier

import 'package:flutter/material.dart';

typedef FutureGenerator<T> = Future<T> Function();

class FutureController<T> extends ValueNotifier<Future<T>?> {
  final FutureGenerator<T> _generator;

  FutureController(this._generator) : super(null) {
    refresh(); // Automatically load initial future
  }

  void refresh() {
    value = _generator();
    notifyListeners();
  }
}

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

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: MyFutureBuilderWidget(),
    );
  }
}

class MyFutureBuilderWidget extends StatefulWidget {
  @override
  _MyFutureBuilderWidgetState createState() => _MyFutureBuilderWidgetState();
}

class _MyFutureBuilderWidgetState extends State<MyFutureBuilderWidget> {
  late FutureController<String> _futureNotifier;

  @override
  void initState() {
    super.initState();
    // Initialize the notifier with the fetchData method.
    _futureNotifier = FutureController<String>(fetchData);
  }

  Future<String> fetchData() async {
    await Future.delayed(Duration(seconds: 5)); // Simulate a network delay
    return "Data Loaded";
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('FutureController with FutureBuilder')),
      body: ValueListenableBuilder<Future<String>?>(
        valueListenable: _futureNotifier,
        builder: (context, future, child) {
          return FutureBuilder<String>(
            future: future,
            builder: (context, snapshot) {
              if (snapshot.connectionState == ConnectionState.waiting) {
                return Center(child: CircularProgressIndicator());
              }
              if (snapshot.hasError) {
                return Center(child: Text('Error: ${snapshot.error}'));
              }
              return Center(child: Text(snapshot.data ?? 'No data'));
            },
          );
        },
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () =>
            _futureNotifier.refresh(),
        child: Icon(Icons.refresh),
      ),
    );
  }
}