Sample for Flutter Tokyo

main.dart

import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';

void main() => runApp(
      const ProviderScope(
        child: MyApp(),
      ),
    );

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

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

final countProvider = StateProvider((ref) {
  return 0;
});

class MyHomePage extends ConsumerWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text(title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: const [
            Text(
              'You have pushed the button this many times:',
            ),
            _CounterText(),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          ref.read(countProvider.notifier).state += 1;
        },
        tooltip: 'Increment',
        child: const Icon(Icons.add),
      ),
    );
  }
}

class _CounterText extends ConsumerWidget {
  const _CounterText();

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final count = ref.watch(countProvider);
    return Text(
      '$count',
      style: Theme.of(context).textTheme.headlineMedium,
    );
  }
}