riverpod/packages/hooks_riverpod/example/lib/main.dart

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

void main() {
  runApp(
    /// [MyApp] is wrapped in a [ProviderScope].
    /// This widget is where the state of most of our providers will be stored.
    /// This replaces `MultiProvider` if you've used `provider` before.
    const ProviderScope(
      child: MyApp(),
    ),
  );
}

/// A provider that creates and listen to a [StateNotifier].
///
/// Providers are declared as global variables.
/// This does not hinder testability, as the state of a provider is instead
/// stored inside a [ProviderScope].
final counterProvider = StateNotifierProvider<Counter, int>((_) => Counter());

/// A simple [StateNotifier] that implements a counter.
///
/// It doesn't have to be a [StateNotifier], and could be anything else such as:
/// - [ChangeNotifier], with [ChangeNotifierProvider]
/// - [Stream], with [StreamProvider]
/// ...
class Counter extends StateNotifier<int> {
  Counter() : super(0);

  void increment() => state++;
}

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

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends HookConsumerWidget {
  const MyHomePage({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Riverpod counter example'),
      ),
      body: Center(
        // HookConsumer is a builder widget that allows you to read providers and utilise hooks.
        child: HookConsumer(
          builder: (context, ref, _) {
            final count = ref.watch(counterProvider);

            return Text(
              '$count',
              style: Theme.of(context).textTheme.headlineMedium,
            );
          },
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () => ref.read(counterProvider.notifier).increment(),
        child: const Icon(Icons.add),
      ),
    );
  }
}