Flutter iOS 音声メモアプリ開発（７）設定画面　SharedPreferences & Riverpod

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

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

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

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

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

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

class _MyHomePageState extends State<MyHomePage>
    with SingleTickerProviderStateMixin {
  late TabController _tabController;

  @override
  void initState() {
    super.initState();
    _tabController = TabController(vsync: this, length: 3);
  }

  @override
  void dispose() {
    _tabController.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Riverpod & SharedPreferences Demo'),
        bottom: TabBar(
          controller: _tabController,
          tabs: const [
            Tab(icon: Icon(Icons.home), text: 'Home'),
            Tab(icon: Icon(Icons.chat_bubble), text: 'Chat Bot'),
            Tab(icon: Icon(Icons.settings), text: 'Settings'),
          ],
        ),
      ),
      body: TabBarView(
        controller: _tabController,
        children: const [
          HomeScreen(),
          ChatBotScreen(),
          SettingScreen(),
        ],
      ),
    );
  }
}

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

  @override
  Widget build(BuildContext context) {
    return const Center(
      child: Text('Home Screen'),
    );
  }
}

final settingsProvider = StateNotifierProvider<SettingsNotifier, Settings>(
    (ref) => SettingsNotifier());

class Settings {
  Settings({this.someValue = ''});
  final String someValue;
}

class SettingsNotifier extends StateNotifier<Settings> {
  SettingsNotifier() : super(Settings()) {
    loadSettings();
  }

  Future<void> loadSettings() async {
    final prefs = await SharedPreferences.getInstance();
    final savedValue = prefs.getString('someValue') ?? '';
    state = Settings(someValue: savedValue);
  }
  Future<void> updateSettings(String newValue) async {
    final prefs = await SharedPreferences.getInstance();
    await prefs.setString('someValue', newValue);
    state = Settings(someValue: newValue);
  }
}

class ChatBotScreen extends ConsumerWidget {
  const ChatBotScreen({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final settings = ref.watch(settingsProvider);
    return Center(
      child: Text('Chat Bot Screen: ${settings.someValue}'),
    );
  }
}

class SettingScreen extends ConsumerWidget {
  const SettingScreen({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final settings = ref.watch(settingsProvider);
    return Center(
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          Text('Settings: ${settings.someValue}'),
          TextFormField(
            initialValue: settings.someValue,
            decoration: const InputDecoration(labelText: 'Enter new value'),
            onChanged: (newValue) {
              ref.read(settingsProvider.notifier).updateSettings(newValue);
            },
          ),
        ],
      ),
    );
  }
}