一、购物车逻辑

1.1 购物车及加减菜

在utils目录下新建CartStore.ets文件，如下：

import { FoodItem } from '../models'// 本地持久化购物车数据
PersistentStorage.persistProp<FoodItem[]>('cartStore', [])export class CartStore {static getCarts() {return AppStorage.get<FoodItem[]>('cartStore') || [] as FoodItem[]}/*** 加菜or减菜* @param foodItem* @param type*/static addOrCutFood(foodItem: FoodItem, type: 'add' | 'cut') {const cartList = CartStore.getCarts()const item = cartList.find((item) => item.id === foodItem.id)// 加菜if (type === 'add') {if (item) {item.count++} else {foodItem.count = 1cartList.unshift(foodItem)}} else { // 减菜if (item && item.count > 0) {item.count--if (item.count === 0) {const index = cartList.findIndex((item) => item.id === foodItem.id)cartList.splice(index, 1)}}}AppStorage.set<FoodItem[]>('cartStore', [...cartList])}
}

1.2 菜品的加减—方案一

实现如下效果，当选择数量大于0时展示-及数量：

改造MTAddCutView，如下：

import { FoodItem } from '../models'
import { CartStore } from '../utils/CartStore'@Preview
@Component
export struct MTAddCutView {// 当前菜品@Require @Prop foodItem: FoodItem = new FoodItem()// 购物车数据@Consume cartList: FoodItem[]// 当前选择数量getCount() {return this.cartList.find(obj => obj.id === this.foodItem.id)?.count || 0}build() {Row({ space: 8 }) {Row() {Image($r('app.media.ic_screenshot_line')).width(10).aspectRatio(1)}.width(16).height(16).justifyContent(FlexAlign.Center).backgroundColor(Color.White).borderRadius(4).border({color: $r('app.color.main_color'),width: 0.5})// 如果为0，则取消展示.visibility(this.getCount() > 0 ? Visibility.Visible : Visibility.Hidden)// 减少菜品.onClick(() => {CartStore.addOrCutFood(this.foodItem, 'cut')})Text(this.getCount().toString()).fontSize(14).visibility(this.getCount() > 0 ? Visibility.Visible : Visibility.Hidden)Row() {Image($r('app.media.ic_public_add_filled')).width(10).aspectRatio(1)}.width(16).height(16).justifyContent(FlexAlign.Center).borderRadius(4).backgroundColor($r('app.color.main_color'))// 添加菜品.onClick(() => {CartStore.addOrCutFood(this.foodItem, 'add')})}}
}

在主页面MeiTuanPage.ets中，通过Watch和StorageProp实现数据动态展示：

// 方案一：使用StorageProp和Watch实现
@StorageProp('cartStore') @Watch('onCartChange') cartData: FoodItem[] = []
// 购物车数据变化发生回调
onCartChange() {this.cartList = CartStore.getCarts()
}

1.3 菜品的加减—方案二

使用事件总线实现事件的发布和订阅。
在CartStore.ets中增加事件发布：

...AppStorage.set<FoodItem[]>('cartStore', [...cartList])
// 方案二：使用事件总线
getContext().eventHub.emit('changeCart')
...

在MeiTuanPage.ets中注册订阅：

aboutToAppear(): void {this.categoryList = mockCategorythis.cartList = CartStore.getCarts()// 方案二：使用事件总线getContext().eventHub.on('changeCart', () => {this.cartList = CartStore.getCarts()})
}

1.4 购物车View完善

购物车展示真实数据及加减菜品：
MTCartView

import { FoodItem } from '../models'
import { MTCartItemView } from './MTCartItemView'@Preview
@Component
export struct MTCartView {@Consume cartList: FoodItem[]build() {Column() {Column() {// 头部Row() {Text('购物车').fontSize(14)Text('清空购物车').fontColor($r('app.color.search_font_color')).fontSize(12)}.width('100%').height(48).justifyContent(FlexAlign.SpaceBetween).padding({ left: 15, right: 15 })// 购物车列表List() {ForEach(this.cartList, (item: FoodItem) => {ListItem() {MTCartItemView({ foodItem: item })}})}.divider({ strokeWidth: 1, color: '#e5e5e5', startMargin: 20, endMargin: 20 })}.backgroundColor(Color.White).padding({bottom: 88}).borderRadius({topLeft: 12,topRight: 12})}.width('100%').height('100%').justifyContent(FlexAlign.End).backgroundColor('rgba(0,0,0,0.5)')}
}

MTCartItemView

import { FoodItem } from '../models'
import { MTAddCutView } from './MTAddCutView'@Preview
@Component
export struct MTCartItemView {foodItem: FoodItem = new FoodItem()build() {Row({ space: 6 }) {Image('https://bkimg.cdn.bcebos.com/pic/4d086e061d950a7bc94a331704d162d9f3d3c9e2').width(42).aspectRatio(1).borderRadius(5)Column({ space: 3 }) {Text(this.foodItem.name)Row() {Text() {Span('￥').fontSize(10)Span(this.foodItem.price.toString()).fontColor($r('app.color.main_color')).fontSize(14).fontWeight(600)}MTAddCutView({ foodItem: this.foodItem })}.width('100%').justifyContent(FlexAlign.SpaceBetween)}.layoutWeight(1).alignItems(HorizontalAlign.Start)}.height(60).alignItems(VerticalAlign.Top).width('100%').padding({ top: 12, left: 15, right: 15, bottom: 12 })}
}

1.5 清空购物车

CartStore.ets中增加清空方法：

static clearCart() {AppStorage.set('cartStore', [])getContext().eventHub.emit('changeCart')
}

购物车View中增加点击事件：

...
Text('清空购物车').fontColor($r('app.color.search_font_color')).fontSize(12).onClick(() => {CartStore.clearCart()})
...

1.5 购物车数量和价格

修改MTBottomView，计算购物车数量和价格：

import { FoodItem } from '../models'@Component
export struct MTBottomView {@ConsumeshowCart: boolean@Consume cartList: FoodItem[]// 获取总数量getTotalCount() {return this.cartList.reduce((pre: number, item: FoodItem) => {return pre + item.count}, 0)}// 获取总价格getTotalPrice() {return this.cartList.reduce((pre: number, item: FoodItem) => {return pre + item.count * item.price}, 0)}build() {Row() {// 小哥+角标Badge({ value: this.getTotalCount().toString(), style: { badgeSize: 18 }, position: BadgePosition.Right }) {Image($r('app.media.ic_public_cart')).height(69).width(47).position({y: -20})}.margin({ left: 28, right: 12 }).onClick(() => {this.showCart = !this.showCart})// 金额+描述Column() {Text() {Span('￥').fontColor(Color.White).fontSize(12)Span(this.getTotalPrice().toString()).fontColor(Color.White).fontSize(25)}Text('预估另需配送费￥5').fontColor($r('app.color.search_font_color')).fontSize(12)}.alignItems(HorizontalAlign.Start).layoutWeight(1)// 去结算Text('去结算').width(80).height(50).fontSize(16).backgroundColor($r('app.color.main_color')).textAlign(TextAlign.Center).borderRadius({topRight: 25,bottomRight: 25})}.height(50).width('88%').margin({ bottom: 20 }).backgroundColor(Color.Black).borderRadius(26)}
}

二、小结

• cartStore应用
• 加减菜逻辑
• 购物车逻辑
• 事件总线