flutter_provider_demo/lib/pages/proxy_provider_page.dart

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

// 用户信息模型
class UserProfile extends ChangeNotifier {
  String _name = "张三";
  int _age = 25;

  String get name => _name;
  int get age => _age;

  void updateName(String newName) {
    _name = newName;
    notifyListeners();
  }

  void incrementAge() {
    _age++;
    notifyListeners();
  }
}

// 购物车模型
class Cart extends ChangeNotifier {
  final List<String> _items = [];
  double _totalPrice = 0;

  List<String> get items => _items;
  double get totalPrice => _totalPrice;

  void addItem(String item, double price) {
    _items.add(item);
    _totalPrice += price;
    notifyListeners();
  }
}

// 使用ProxyProvider组合用户信息和购物车信息
class UserCartSummary {
  final UserProfile user;
  final Cart cart;

  UserCartSummary(this.user, this.cart);

  String get summary =>
      '${user.name}的购物车共有${cart.items.length}件商品，总价：¥${cart.totalPrice}';
}

// 格式化显示
class FormattedCart {
  final Cart cart;

  FormattedCart(this.cart);

  String get itemCount => '商品数量: ${cart.items.length}';
  String get formattedTotal => '总价: ¥${cart.totalPrice.toStringAsFixed(2)}';
  String get itemsList => cart.items.join(', ');
}

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

  @override
  Widget build(BuildContext context) {
    return MultiProvider(
      providers: [
        // 基础数据提供者
        ChangeNotifierProvider(create: (_) => UserProfile()),
        ChangeNotifierProvider(create: (_) => Cart()),

        // 使用ProxyProvider2组合两个Provider的数据
        ProxyProvider2<UserProfile, Cart, UserCartSummary>(
          update: (_, userProfile, cart, __) =>
              UserCartSummary(userProfile, cart),
        ),

        // 使用ProxyProvider转换数据格式
        ProxyProvider<Cart, FormattedCart>(
          update: (_, cart, __) => FormattedCart(cart),
        ),
      ],
      child: Scaffold(
        appBar: AppBar(
          title: const Text('ProxyProvider示例'),
        ),
        body: const Padding(
          padding: EdgeInsets.all(16.0),
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.start,
            children: [
              UserProfileSection(),
              SizedBox(height: 20),
              CartSection(),
              SizedBox(height: 20),
              SummarySection(),
            ],
          ),
        ),
      ),
    );
  }
}

// 用户信息展示和操作部分
class UserProfileSection extends StatelessWidget {
  const UserProfileSection({super.key});

  @override
  Widget build(BuildContext context) {
    return Card(
      child: Padding(
        padding: const EdgeInsets.all(8.0),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            const Text('用户信息',
                style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold)),
            const SizedBox(height: 8),
            // 使用Consumer监听用户信息变化
            Consumer<UserProfile>(
              builder: (_, user, __) => Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  Text('姓名: ${user.name}'),
                  Text('年龄: ${user.age}'),
                ],
              ),
            ),
            const SizedBox(height: 8),
            Row(
              children: [
                ElevatedButton(
                  onPressed: () => context.read<UserProfile>().updateName(
                      context.read<UserProfile>().name == "张三" ? "李四" : "张三"),
                  child: const Text('切换用户'),
                ),
                const SizedBox(width: 8),
                ElevatedButton(
                  onPressed: () => context.read<UserProfile>().incrementAge(),
                  child: const Text('增加年龄'),
                ),
              ],
            ),
          ],
        ),
      ),
    );
  }
}

// 购物车操作部分
class CartSection extends StatelessWidget {
  const CartSection({super.key});

  @override
  Widget build(BuildContext context) {
    return Card(
      child: Padding(
        padding: const EdgeInsets.all(8.0),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            const Text('购物车',
                style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold)),
            const SizedBox(height: 8),
            // 使用Consumer监听购物车数据变化
            Consumer<FormattedCart>(
              builder: (_, formattedCart, __) => Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  Text(formattedCart.itemCount),
                  Text(formattedCart.formattedTotal),
                  Text('商品列表: ${formattedCart.itemsList}'),
                ],
              ),
            ),
            const SizedBox(height: 8),
            Row(
              children: [
                ElevatedButton(
                  onPressed: () => context.read<Cart>().addItem('商品A', 99.9),
                  child: const Text('添加商品A'),
                ),
                const SizedBox(width: 8),
                ElevatedButton(
                  onPressed: () => context.read<Cart>().addItem('商品B', 199.9),
                  child: const Text('添加商品B'),
                ),
              ],
            ),
          ],
        ),
      ),
    );
  }
}

// 汇总信息展示部分
class SummarySection extends StatelessWidget {
  const SummarySection({super.key});

  @override
  Widget build(BuildContext context) {
    return Card(
      child: Padding(
        padding: const EdgeInsets.all(8.0),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            const Text('汇总信息',
                style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold)),
            const SizedBox(height: 8),
            // 使用Consumer监听组合后的数据变化
            Consumer<UserCartSummary>(
              builder: (_, summary, __) => Text(
                summary.summary,
                style: const TextStyle(fontSize: 16),
              ),
            ),
          ],
        ),
      ),
    );
  }
}