注意：前端 vuex 数据，后端数据库数据都要

1. 注册点击事件

2. 页面中dispatch action

3. 提供action函数

4. 提供mutation处理函数

---

底部总价展示

1. 提供getters

2. 动态渲染

---

完整代码

main.js

import Vue from 'vue'
import App from './App.vue'
import store from './store'

Vue.config.productionTip = false

new Vue({
  store,
  render: h => h(App)
}).$mount('#app')

App.vue

<template>
  <div class="app-container">
    <!-- Header 区域 -->
    <cart-header></cart-header>

    <!-- 商品 Item 项组件 -->
    <cart-item v-for="item in list" :key="item.id" :item="item"></cart-item>

    <!-- Foote 区域 -->
    <cart-footer></cart-footer>
  </div>
</template>

<script>
import CartHeader from '@/components/cart-header.vue'
import CartFooter from '@/components/cart-footer.vue'
import CartItem from '@/components/cart-item.vue'

import { mapState } from 'vuex'

export default {
  name: 'App',
  created () {
    this.$store.dispatch('cart/getList')
  },
  computed: {
    ...mapState('cart', ['list'])
  },
  components: {
    CartHeader,
    CartFooter,
    CartItem
  }
}
</script>

<style lang="less" scoped>
.app-container {
  padding: 50px 0;
  font-size: 14px;
}
</style>

store/index.js

import Vue from 'vue'
import Vuex from 'vuex'
import cart from './modules/cart'

Vue.use(Vuex)

export default new Vuex.Store({
  modules: {
    cart
  }
})

store/modules/cart.js

import axios from 'axios'
export default {
  namespaced: true,
  // 这种语法是官方在分模块时推荐的一种语法，为的就是每个模块数据的独立性，推荐你写成一个函数，函数里面return即可
  state () {
    return {
      // 购物车数据 [{}, {}]
      list: []
    }
  },
  mutations: {
    updateList (state, newList) {
      state.list = newList
    },
    // obj: { id: xxx, newCount: xxx }
    updateCount (state, obj) {
      // 根据 id 找到对应的对象，更新count属性即可
      const goods = state.list.find(item => item.id === obj.id)
      goods.count = obj.newCount
    }
  },
  actions: {
    // 请求方式：get
    // 请求地址：http://localhost:3000/cart
    async getList (context) {
      const res = await axios.get('http://localhost:3000/cart')
      context.commit('updateList', res.data)
    },
    // 请求方式：patch
    // 请求地址：http://localhost:3000/cart/:id值  表示修改的是哪个对象
    // 请求参数：
    // {
    //   name: '新值',  【可选】
    //   price: '新值', 【可选】
    //   count: '新值', 【可选】
    //   thumb: '新值'  【可选】
    // }
    async updateCountAsync (context, obj) {
      // 将修改更新同步到后台服务器，在db/index.js里的数据也会一起更新
      await axios.patch(`http://localhost:3000/cart/${obj.id}`, {
        count: obj.newCount
      })
      // 将修改更新同步到 vuex
      context.commit('updateCount', {
        id: obj.id,
        newCount: obj.newCount
      })
    }
  },
  getters: {
    // 商品总数量 累加count
    total (state) {
      return state.list.reduce((sum, item) => sum + item.count, 0)
    },
    // 商品总价格 累加count * price
    totalPrice (state) {
      return state.list.reduce((sum, item) => sum + item.count * item.price, 0)
    }
  }
}

components/cart-item.vue

<template>
  <div class="goods-container">
    <!-- 左侧图片区域 -->
    <div class="left">
      <img :src="item.thumb" class="avatar" alt="">
    </div>
    <!-- 右侧商品区域 -->
    <div class="right">
      <!-- 标题 -->
      <div class="title">{{ item.name }}</div>
      <div class="info">
        <!-- 单价 -->
        <span class="price">￥{{ item.price }}</span>
        <div class="btns">
          <!-- 按钮区域 -->
          <button class="btn btn-light" @click="btnClick(-1)">-</button>
          <span class="count">{{ item.count }}</span>
          <button class="btn btn-light" @click="btnClick(1)">+</button>
        </div>
      </div>
    </div>
  </div>
</template>

<script>
export default {
  name: 'CartItem',
  methods: {
    btnClick (step) {
      const newCount = this.item.count + step
      const id = this.item.id

      if (newCount < 1) return

      this.$store.dispatch('cart/updateCountAsync', {
        id,
        newCount
      })
    }
  },
  props: {
    item: {
      type: Object,
      required: true
    }
  }
}
</script>

<style lang="less" scoped>
.goods-container {
  display: flex;
  padding: 10px;
  + .goods-container {
    border-top: 1px solid #f8f8f8;
  }
  .left {
    .avatar {
      width: 100px;
      height: 100px;
    }
    margin-right: 10px;
  }
  .right {
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    flex: 1;
    .title {
      font-weight: bold;
    }
    .info {
      display: flex;
      justify-content: space-between;
      align-items: center;
      .price {
        color: red;
        font-weight: bold;
      }
      .btns {
        .count {
          display: inline-block;
          width: 30px;
          text-align: center;
        }
      }
    }
  }
}

.custom-control-label::before,
.custom-control-label::after {
  top: 3.6rem;
}
</style>

component/cart-footer.vue

<template>
  <div class="footer-container">
    <!-- 中间的合计 -->
    <div>
      <span>共 {{ total }} 件商品，合计：</span>
      <span class="price">￥{{ totalPrice }}</span>
    </div>
    <!-- 右侧结算按钮 -->
    <button class="btn btn-success btn-settle">结算</button>
  </div>
</template>

<script>
import { mapGetters } from 'vuex'
export default {
  name: 'CartFooter',
  computed: {
    ...mapGetters('cart', ['total', 'totalPrice'])
  }
}
</script>

<style lang="less" scoped>
.footer-container {
  background-color: white;
  height: 50px;
  border-top: 1px solid #f8f8f8;
  display: flex;
  justify-content: flex-end;
  align-items: center;
  padding: 0 10px;
  position: fixed;
  bottom: 0;
  left: 0;
  width: 100%;
  z-index: 999;
}

.price {
  color: red;
  font-size: 13px;
  font-weight: bold;
  margin-right: 10px;
}

.btn-settle {
  height: 30px;
  min-width: 80px;
  margin-right: 20px;
  border-radius: 20px;
  background: #42b983;
  border: none;
  color: white;
}
</style>