效果图

index.js文件

import Vue from "vue";
import Vuex from 'vuex'

Vue.use(Vuex)

export default new Vuex.Store({
    state: {
        shopsList: [{
                goodsName: "手机1", //商品名
                goodsAmount: 0, //购买的商品数量
                goodsPrice: 100, //单个商品价格
                totalPrice: 0,
                id: 1,

            },
            {
                goodsName: "手机2", //商品名
                goodsAmount: 0, //购买的商品数量
                goodsPrice: 200, //单个商品价格
                totalPrice: 0,
                id: 2,

            },
            {
                goodsName: "手机3", //商品名
                goodsAmount: 0, //购买的商品数量
                goodsPrice: 300, //单个商品价格
                totalPrice: 0,
                id: 3,

            },
            {
                goodsName: "手机4", //商品名
                goodsAmount: 0, //购买的商品数量
                goodsPrice: 400, //单个商品价格
                totalPrice: 0,
                id: 4,

            },
        ],

        goodsNumber: 0
    },
    mutations: {
        // 添加商品
        addGoodsMutations(state, goods) {
            state.shopsList.forEach((item) => {
                if (item.id === goods.id) {
                    item.goodsAmount++
                }
            })
        },
        // 减去商品
        reduceGoodsMutations(state, goods) {
            if (goods.goodsAmount === 0) {
                alert("商品已经不能再减啦")
                return
            }
            state.shopsList.forEach((item) => {
                if (item.id === goods.id) {
                    item.goodsAmount--
                }

            })


        },
        totalMutations(state, goods) {
            state.shopsList.forEach((item) => {
                if (item.id === goods.id) {
                    item.totalPrice = item.goodsAmount * item.goodsPrice
                }

            })
        },
    },
    actions: {

        addGoodsActions({
            commit
        }, item) {
            commit('addGoodsMutations', item)
        },
        reduceGoodsActions({
            commit
        }, item) {
            commit('reduceGoodsMutations', item)
        },
        totalAction({
            commit
        }, item) {
            commit('totalMutations', item)
        }
    },
    getters: {},
    modules: {}
})

页面

<template>
  <div class="box">
    <div class="content" v-for="(item, index) in shopsList" :key="index">
      <div>
        名称:{{ item.goodsName }} 价钱:{{ item.goodsPrice }}
        购买数量:
        <el-button style="margin-right: 5px" @click="reduce(item)">-</el-button>
        <span>{{ item.goodsAmount }}</span>
        <el-button style="margin-left: 5px" @click="add(item)">+</el-button>
        <span>总价钱：{{ item.totalPrice }}</span>
      </div>
    </div>
  </div>
</template>

<script>
import { mapState, mapMutations, mapActions } from "vuex";
export default {
  mounted() {},
  data() {
    return {};
  },
  computed: {
    ...mapState(["shopsList", "totalPrice", "goodsNumber"]),
  },
  methods: {
    ...mapMutations(["addGoodsMutations", "reduceGoodsMutations"]),
    ...mapActions(["addGoodsActions", "reduceGoodsActions", "totalAction"]),
    // 减少商品数量
    reduce(item) {
      this.reduceGoodsActions(item);
      this.totalAction(item);
    },
    // 增加商品数量
    add(item) {
      this.addGoodsActions(item);
      this.totalAction(item);
    },
  },
};
</script>

<style>
.box {
  width: 400px;
  height: 200px;
  border: 1px solid black;
}
.content {
  height: 50px;
  display: flex;
  justify-content: space-evenly;
  align-items: center;
}
</style>

先这样吧，后续将再完善