从官方下载代码
https://developers.weixin.qq.com/miniprogram/dev/framework/ability/custom-tabbar.html

1、把custom-tab-bar 文件放置 pages同级
修改下 custom-tab-bar 下的 JS文件

Component({data: {selected: 0,color: "#7A7E83",selectedColor: "#3cc51f",list: [{pagePath: "/pages/index/index",iconPath: "/static/images/ico/home.png",selectedIconPath: "/static/images/ico/home.png",text: "A"}, {pagePath: "/pages/product/product",iconPath: "/static/images/ico/home.png",selectedIconPath: "/static/images/ico/home.png",text: "B"},{pagePath: "/pages/news/news",iconPath: "/static/images/ico/home.png",selectedIconPath: "/static/images/ico/home.png",text: "C"},{pagePath: "/pages/my/my",iconPath: "/static/images/ico/home.png",selectedIconPath: "/static/images/ico/home.png",text: "D"},
]},attached() {},methods: {switchTab(e) {const data = e.currentTarget.datasetconst url = data.pathwx.switchTab({url})//   this.setData({  这部分注销，到其他页进行赋值//     selected: data.index//   })}}
})

2、跳转到指定页面时，在当页面JS上加上代码：

onShow: function () {  //上面注销得部分， 在A-D页面对应上，  A页面=0 ，B=1 以此类推if (typeof this.getTabBar === 'function' &&  this.getTabBar()) {this.getTabBar().setData({selected: 0     //这里的数字设置当前页面在tabbar里对应的序列，从0开始})}}

3、在app.json 开启自定义tab

  "tabBar": {"custom": true,  //开启"color": "#767676","selectedColor": "#004F8A","backgroundColor": "#fff","borderStyle": "black","list": [

4、在app.js 隐藏原生得JS

// app.js
App({onLaunch() {wx.hideTabBar(); //隐藏原生得tab bar // 展示本地存储能力const logs = wx.getStorageSync('logs') || []logs.unshift(Date.now())wx.setStorageSync('logs', logs)