【Flutter】MVVMをRiverpodで実装する！サンプルを用いて解説

dependencies:
  build_runner: ^2.1.8
  flutter:
    sdk: flutter
  flutter_riverpod: ^1.0.3
  freezed: ^1.1.1
  freezed_annotation: ^1.1.0

dev_dependencies:
  flutter_lints: ^1.0.0
  flutter_test:
    sdk: flutter

import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:flutter_mvvm/view/home_page.dart';

void main() {
  runApp(const ProviderScope(child: MyApp()));
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Flutter MVVM',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: HomePage(),
    );
  }
}

import 'package:flutter/foundation.dart';
import 'package:freezed_annotation/freezed_annotation.dart';

// 生成されるファイル名を指定する（ `生成元ファイル名.freezed.dart` ）
part 'home_page_state.freezed.dart';

@freezed
class HomePageState with _$HomePageState {
  const factory HomePageState({
    @Default(0) int mainCount,
    @Default(0) int subCount,
  }) = _HomePageState;
}

flutter pub run build_runner watch --delete-conflicting-outputs

import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:flutter_mvvm/model/home_page_state.dart';

class HomePageNotifier extends StateNotifier<HomePageState> {
  // 初期値の指定
  HomePageNotifier() : super(const HomePageState());

  // メインカウントを+1する
  void increaseMainCount() async {
    state = state.copyWith(mainCount: state.mainCount + 1);
  }

  // サブカウントを+1する
  void increaseSubCount() async {
    state = state.copyWith(subCount: state.subCount + 1);
  }

  // すべてのカウントを0に戻す
  void resetAllCount() async {
    state = state.copyWith(
      mainCount: 0,
      subCount: 0,
    );
  }
}

// HomePageNotifierの状態を管理する
final homePageProvider =
    StateNotifierProvider.autoDispose<HomePageNotifier, HomePageState>(
  (ref) => HomePageNotifier(),
);

import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:flutter_mvvm/model/home_page_state.dart';
import 'package:flutter_mvvm/view/home_page.dart';
import 'package:flutter/material.dart';
import 'package:flutter_mvvm/view_model/home_page_notifier.dart';

class HomePage extends ConsumerWidget {
  const HomePage({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    // state（状態）
    final _homePageState = ref.watch(homePageProvider);
    // provider（状態の操作）
    final _homePageNotifier = ref.watch(homePageProvider.notifier);
    return Scaffold(
      appBar: AppBar(title: const Text('Flutter MVVM')),
      floatingActionButton: FloatingActionButton(
        onPressed: _homePageNotifier.resetAllCount,
        child: const Icon(Icons.exposure_zero),
      ),
      body: ListView(
        children: [
          ListTile(
            title: Text('Main Count ${_homePageState.mainCount}'),
            onTap: _homePageNotifier.increaseMainCount,
          ),
          ListTile(
            title: Text('Sub Count ${_homePageState.subCount}'),
            onTap: _homePageNotifier.increaseSubCount,
          ),
        ],
      ),
    );
  }
}