完成购物车功能

src/hooks/useCart.ts

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+import { useState, useEffect } from 'react';
+import Taro from '@tarojs/taro';
+
+// 购物车商品接口
+export interface CartItem {
+  goodsId: number;
+  name: string;
+  price: string;
+  image: string;
+  quantity: number;
+  addTime: number;
+}
+
+// 购物车Hook
+export const useCart = () => {
+  const [cartItems, setCartItems] = useState<CartItem[]>([]);
+  const [cartCount, setCartCount] = useState(0);
+
+  // 从本地存储加载购物车数据
+  const loadCartFromStorage = () => {
+    try {
+      const cartData = Taro.getStorageSync('cart_items');
+      if (cartData) {
+        const items = JSON.parse(cartData) as CartItem[];
+        setCartItems(items);
+        updateCartCount(items);
+      }
+    } catch (error) {
+      console.error('加载购物车数据失败:', error);
+    }
+  };
+
+  // 保存购物车数据到本地存储
+  const saveCartToStorage = (items: CartItem[]) => {
+    try {
+      Taro.setStorageSync('cart_items', JSON.stringify(items));
+    } catch (error) {
+      console.error('保存购物车数据失败:', error);
+    }
+  };
+
+  // 更新购物车数量
+  const updateCartCount = (items: CartItem[]) => {
+    const count = items.reduce((total, item) => total + item.quantity, 0);
+    setCartCount(count);
+  };
+
+  // 添加商品到购物车
+  const addToCart = (goods: {
+    goodsId: number;
+    name: string;
+    price: string;
+    image: string;
+  }, quantity: number = 1) => {
+    const newItems = [...cartItems];
+    const existingItemIndex = newItems.findIndex(item => item.goodsId === goods.goodsId);
+
+    if (existingItemIndex >= 0) {
+      // 如果商品已存在，增加数量
+      newItems[existingItemIndex].quantity += quantity;
+    } else {
+      // 如果商品不存在，添加新商品
+      const newItem: CartItem = {
+        goodsId: goods.goodsId,
+        name: goods.name,
+        price: goods.price,
+        image: goods.image,
+        quantity,
+        addTime: Date.now()
+      };
+      newItems.push(newItem);
+    }
+
+    setCartItems(newItems);
+    updateCartCount(newItems);
+    saveCartToStorage(newItems);
+
+    // 显示成功提示
+    Taro.showToast({
+      title: '加入购物车成功',
+      icon: 'success',
+      duration: 1500
+    });
+  };
+
+  // 从购物车移除商品
+  const removeFromCart = (goodsId: number) => {
+    const newItems = cartItems.filter(item => item.goodsId !== goodsId);
+    setCartItems(newItems);
+    updateCartCount(newItems);
+    saveCartToStorage(newItems);
+  };
+
+  // 更新商品数量
+  const updateQuantity = (goodsId: number, quantity: number) => {
+    if (quantity <= 0) {
+      removeFromCart(goodsId);
+      return;
+    }
+
+    const newItems = cartItems.map(item => 
+      item.goodsId === goodsId ? { ...item, quantity } : item
+    );
+    setCartItems(newItems);
+    updateCartCount(newItems);
+    saveCartToStorage(newItems);
+  };
+
+  // 清空购物车
+  const clearCart = () => {
+    setCartItems([]);
+    setCartCount(0);
+    Taro.removeStorageSync('cart_items');
+  };
+
+  // 获取购物车总价
+  const getTotalPrice = () => {
+    return cartItems.reduce((total, item) => {
+      return total + (parseFloat(item.price) * item.quantity);
+    }, 0).toFixed(2);
+  };
+
+  // 检查商品是否在购物车中
+  const isInCart = (goodsId: number) => {
+    return cartItems.some(item => item.goodsId === goodsId);
+  };
+
+  // 获取商品在购物车中的数量
+  const getItemQuantity = (goodsId: number) => {
+    const item = cartItems.find(item => item.goodsId === goodsId);
+    return item ? item.quantity : 0;
+  };
+
+  // 初始化时加载购物车数据
+  useEffect(() => {
+    loadCartFromStorage();
+  }, []);
+
+  return {
+    cartItems,
+    cartCount,
+    addToCart,
+    removeFromCart,
+    updateQuantity,
+    clearCart,
+    getTotalPrice,
+    isInCart,
+    getItemQuantity,
+    loadCartFromStorage
+  };
+};