Flutter: Local Storage

import 'package:flutter_secure_storage/flutter_secure_storage.dart';
import 'package:hive/hive.dart';
import 'package:shared_preferences/shared_preferences.dart';

// ⚙️ Install dependency: flutter pub add flutter_secure_storage hive hive_flutter shared_preferences

// Layered storage strategy
final token = await SecureStorage.getToken();      // Encrypted
final cached = await HiveBox.getProducts();         // NoSQL
final theme = await SharedPreferences.getTheme();   // KV

> Output: Run on a local Flutter SDK (Flutter 3.x / Dart 3.x). The Piston server does not have Flutter installed — use `flutter run` on your local machine for hands-on comparison. Actual UI/state may vary slightly by platform.

> Output: Run on a local Flutter SDK (Flutter 3.x / Dart 3.x). The Piston server does not have Flutter installed — use `flutter run` on your local machine for hands-on comparison. Actual UI/state may vary slightly by platform.

> Output: Run on a local Flutter SDK (Flutter 3.x / Dart 3.x). The Piston server does not have Flutter installed — use `flutter run` on your local machine for hands-on comparison. Actual UI/state may vary slightly by platform.

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

// ⚙️ Install dependency: flutter pub add shared_preferences

class UserPreferences {
  static const _keyTheme = 'theme_mode';
  static const _keyLocale = 'locale';
  static const _keyFirstLaunch = 'first_launch';
  static const _keyCurrency = 'currency';

  static Future<ThemeMode> getTheme() async {
    final prefs = await SharedPreferences.getInstance();
    final value = prefs.getString(_keyTheme);
    return ThemeMode.values.firstWhere((m) => m.name == value, orElse: () => ThemeMode.system);
  }

  static Future<void> setTheme(ThemeMode mode) async {
    final prefs = await SharedPreferences.getInstance();
    await prefs.setString(_keyTheme, mode.name);
  }

  static Future<bool> isFirstLaunch() async {
    final prefs = await SharedPreferences.getInstance();
    return prefs.getBool(_keyFirstLaunch) ?? true;
  }

  static Future<void> setFirstLaunchDone() async {
    final prefs = await SharedPreferences.getInstance();
    await prefs.setBool(_keyFirstLaunch, false);
  }

  static Future<String> getCurrency() async {
    final prefs = await SharedPreferences.getInstance();
    return prefs.getString(_keyCurrency) ?? 'USD';
  }

  static Future<void> setCurrency(String currency) async {
    final prefs = await SharedPreferences.getInstance();
    await prefs.setString(_keyCurrency, currency);
  }
}

> Output: Run on a local Flutter SDK (Flutter 3.x / Dart 3.x). The Piston server does not have Flutter installed — use `flutter run` on your local machine for hands-on comparison. Actual UI/state may vary slightly by platform.

> Output: Run on a local Flutter SDK (Flutter 3.x / Dart 3.x). The Piston server does not have Flutter installed — use `flutter run` on your local machine for hands-on comparison. Actual UI/state may vary slightly by platform.

import 'package:flutter/material.dart';

// Custom class definition source:
// - UserPreferences: see Lesson 4 SharedPreferences example in this lesson

class SplashPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    _checkFirstLaunch(context);
    return const Scaffold(body: Center(child: CircularProgressIndicator()));
  }

  Future<void> _checkFirstLaunch(BuildContext context) async {
    final isFirst = await UserPreferences.isFirstLaunch();
    if (isFirst) {
      Navigator.pushReplacementNamed(context, '/onboarding');
      await UserPreferences.setFirstLaunchDone();
    } else {
      Navigator.pushReplacementNamed(context, '/home');
    }
  }
}

> Output: Run on a local Flutter SDK (Flutter 3.x / Dart 3.x). The Piston server does not have Flutter installed — use `flutter run` on your local machine for hands-on comparison. Actual UI/state may vary slightly by platform.

> Output: Run on a local Flutter SDK (Flutter 3.x / Dart 3.x). The Piston server does not have Flutter installed — use `flutter run` on your local machine for hands-on comparison. Actual UI/state may vary slightly by platform.

import 'package:hive/hive.dart';
import 'package:hive_flutter/hive_flutter.dart';

// ⚙️ Install dependency: flutter pub add hive hive_flutter
// ⚙️ Dev dependency: flutter pub add --dev hive_generator build_runner

// Custom class definition source:
// - Product: see Lesson 11 json_serializable model (simplified version below)
/*
class Product {
  final int id;
  final String name;
  final double price;
  final String imageUrl;
  final String category;
  const Product({required this.id, required this.name, required this.price,
    required this.imageUrl, required this.category});
}
*/

// Model with Hive adapter
@HiveType(typeId: 0)
class ProductHive extends HiveObject {
  @HiveField(0) late int id;
  @HiveField(1) late String name;
  @HiveField(2) late double price;
  @HiveField(3) late String imageUrl;
  @HiveField(4) late String category;
}

// Initialize Hive
Future<void> initHive() async {
  await Hive.initFlutter();
  Hive.registerAdapter(ProductHiveAdapter());
  await Hive.openBox<ProductHive>('products');
  await Hive.openBox('cart');
}

// Product cache repository
class ProductCache {
  static const _boxName = 'products';

  static Future<void> saveProducts(List<Product> products) async {
    final box = Hive.box<ProductHive>(_boxName);
    await box.clear();
    for (final p in products) {
      await box.put(p.id, ProductHive()
        ..id = p.id
        ..name = p.name
        ..price = p.price
        ..imageUrl = p.imageUrl
        ..category = p.category);
    }
  }

  static Future<List<Product>> getProducts() async {
    final box = Hive.box<ProductHive>(_boxName);
    if (box.isEmpty) return [];
    return box.values.map((h) => Product(
      id: h.id, name: h.name, price: h.price,
      imageUrl: h.imageUrl, category: h.category,
    )).toList();
  }

  static Future<void> clearCache() async {
    final box = Hive.box<ProductHive>(_boxName);
    await box.clear();
  }
}

> Output: Run on a local Flutter SDK (Flutter 3.x / Dart 3.x). The Piston server does not have Flutter installed — use `flutter run` on your local machine for hands-on comparison. Actual UI/state may vary slightly by platform.

> Output: Run on a local Flutter SDK (Flutter 3.x / Dart 3.x). The Piston server does not have Flutter installed — use `flutter run` on your local machine for hands-on comparison. Actual UI/state may vary slightly by platform.

import 'package:hive/hive.dart';

// ⚙️ Install dependency: flutter pub add hive hive_flutter

// Custom class definition source:
// - CartItem: see Lesson 12 CartNotifier example

class CartStorage {
  static const _boxName = 'cart';

  static Future<void> saveCart(List<CartItem> items) async {
    final box = Hive.box(_boxName);
    await box.clear();
    await box.put('items', items.map((i) => {
      'product_id': i.product.id,
      'quantity': i.quantity,
    }).toList());
  }

  static Future<List<Map<String, dynamic>>> loadCart() async {
    final box = Hive.box(_boxName);
    final data = box.get('items');
    return data != null ? List<Map<String, dynamic>>.from(data) : [];
  }
}

> Output: Run on a local Flutter SDK (Flutter 3.x / Dart 3.x). The Piston server does not have Flutter installed — use `flutter run` on your local machine for hands-on comparison. Actual UI/state may vary slightly by platform.

> Output: Run on a local Flutter SDK (Flutter 3.x / Dart 3.x). The Piston server does not have Flutter installed — use `flutter run` on your local machine for hands-on comparison. Actual UI/state may vary slightly by platform.

import 'package:drift/drift.dart';
import 'package:drift/native.dart';

// ⚙️ Install dependency: flutter pub add drift drift_flutter sqlite3_flutter_libs
// ⚙️ Dev dependency: flutter pub add --dev drift_dev build_runner

// Table definition
class Orders extends Table {
  IntColumn get id => integer().autoIncrement()();
  TextColumn get orderNumber => text().withLength(min: 8, max: 20)();
  RealColumn get total => real()();
  TextColumn get status => text().withDefault(const Constant('pending'))();
  DateTimeColumn get createdAt => dateTime().withDefault(currentDateAndTime)();
  TextColumn get currency => text().withDefault(const Constant('USD'))();
}

class OrderItems extends Table {
  IntColumn get id => integer().autoIncrement()();
  IntColumn get orderId => integer().references(Orders, #id)();
  TextColumn get productName => text()();
  RealColumn get price => real()();
  IntColumn get quantity => integer()();
}

// Database class
@DriftDatabase(tables: [Orders, OrderItems])
class AppDatabase extends _$AppDatabase {
  AppDatabase() : super(NativeDatabase.memory());

  @override
  int get schemaVersion => 1;

  // Create order
  Future<int> createOrder(OrdersCompanion order) =>
      into(orders).insert(order);

  // Get order with items
  Future<List<OrderWithItems>> getOrderWithItems(int orderId) {
    final query = select(orders).join([
      leftOuterJoin(orderItems, orderItems.orderId.equalsExp(orders.id)),
    ])..where(orders.id.equals(orderId));
    return query.map((row) {
      final order = row.readTable(orders);
      final item = row.readTableOrNull(orderItems);
      return OrderWithItems(order: order, item: item);
    }).toList();
  }

  // Get recent orders
  Future<List<Order>> getRecentOrders() =>
      (select(orders)..orderBy([(t) => OrderingTerm.desc(t.createdAt)])
        ..limit(20)).get();
}

> Output: Run on a local Flutter SDK (Flutter 3.x / Dart 3.x). The Piston server does not have Flutter installed — use `flutter run` on your local machine for hands-on comparison. Actual UI/state may vary slightly by platform.

> Output: Run on a local Flutter SDK (Flutter 3.x / Dart 3.x). The Piston server does not have Flutter installed — use `flutter run` on your local machine for hands-on comparison. Actual UI/state may vary slightly by platform.

import 'package:flutter_secure_storage/flutter_secure_storage.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/services.dart';

// ⚙️ Install dependency: flutter pub add flutter_secure_storage

class SecureStorage {
  static const _storage = FlutterSecureStorage(
    aOptions: AndroidOptions(encryptedSharedPreferences: true),
    iOptions: IOSOptions(accessibility: KeychainAccessibility.first_unlock),
  );

  static const _keyAccessToken = 'access_token';
  static const _keyRefreshToken = 'refresh_token';
  static const _keyUserId = 'user_id';

  static Future<void> saveTokens({
    required String accessToken,
    required String refreshToken,
    required String userId,
  }) async {
    await _storage.write(key: _keyAccessToken, value: accessToken);
    await _storage.write(key: _keyRefreshToken, value: refreshToken);
    await _storage.write(key: _keyUserId, value: userId);
  }

  static Future<String?> getAccessToken() =>
      _storage.read(key: _keyAccessToken);

  static Future<String?> getRefreshToken() =>
      _storage.read(key: _keyRefreshToken);

  static Future<void> clearAll() => _storage.deleteAll();

  static Future<bool> isLoggedIn() async {
    final token = await getAccessToken();
    return token != null && token.isNotEmpty;
  }
}

> Output: Run on a local Flutter SDK (Flutter 3.x / Dart 3.x). The Piston server does not have Flutter installed — use `flutter run` on your local machine for hands-on comparison. Actual UI/state may vary slightly by platform.

import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:riverpod_annotation/riverpod_annotation.dart';
import 'package:shared_preferences/shared_preferences.dart';

// ⚙️ Install dependency: flutter pub add flutter_riverpod riverpod_annotation shared_preferences
// ⚙️ Dev dependency: flutter pub add --dev riverpod_generator build_runner

// Custom class definition sources:
// - SecureStorage: see Lesson 7 Flutter Secure Storage in this lesson
// - Product: see Lesson 11 json_serializable model
// - User/AuthService: see Lesson 14 Auth Notifier
// - productRepositoryProvider: see Lesson 14 ProductRepository

// storage_provider.dart - Riverpod integration
final sharedPreferencesProvider = Provider<SharedPreferences>((ref) {
  throw UnimplementedError('Override in main');
});

final secureStorageProvider = Provider<SecureStorage>((ref) => SecureStorage());

final productCacheProvider = Provider<ProductCache>((ref) => ProductCache());

// Auth state with persistent token
@riverpod
class Auth extends _$Auth {
  @override
  Future<User?> build() async {
    final storage = ref.read(secureStorageProvider);
    final token = await storage.getAccessToken();
    if (token == null) return null;
    // Validate token with API
    try {
      final user = await AuthService.validateToken(token);
      return user;
    } catch (_) {
      await storage.clearAll();
      return null;
    }
  }

  Future<void> login(String email, String password) async {
    state = const AsyncLoading();
    state = await AsyncValue.guard(() async {
      final result = await AuthService.login(email, password);
      await ref.read(secureStorageProvider).saveTokens(
        accessToken: result.accessToken,
        refreshToken: result.refreshToken,
        userId: result.user.id,
      );
      return result.user;
    });
  }

  Future<void> logout() async {
    await ref.read(secureStorageProvider).clearAll();
    state = const AsyncData(null);
  }
}

// Product with offline cache
@riverpod
class Products extends _$Products {
  @override
  Future<List<Product>> build() async {
    final cache = ref.read(productCacheProvider);
    // Try cache first
    final cached = await cache.getProducts();
    if (cached.isNotEmpty) return cached;
    // Fallback to API
    return _loadFromApi();
  }

  Future<List<Product>> _loadFromApi() async {
    final repo = ref.read(productRepositoryProvider);
    final products = await repo.getProducts();
    await ref.read(productCacheProvider).saveProducts(products);
    return products;
  }

  Future<void> refresh() async {
    state = const AsyncLoading();
    state = await AsyncValue.guard(() => _loadFromApi());
  }
}

> Output: Run on a local Flutter SDK (Flutter 3.x / Dart 3.x). The Piston server does not have Flutter installed — use `flutter run` on your local machine for hands-on comparison. Actual UI/state may vary slightly by platform.