1.首先建立 custom-tab-bar 文件夹  包含 index.js  index.json index.wxml

// index.js
Component({
  data: {
    selected: 0,
    color: "#7A7E83",
    selectedColor: "#3cc51f",
    list: [{
      pagePath: "/pages/tabBar/home/home",
      iconPath: "/image/icon_home_no.png",
      selectedIconPath: "/image/icon_home.png",
      text: "首页"
    }, {
      pagePath: "/pages/tabBar/good/good",
      iconPath: "/image/icon_good_no.png",
      selectedIconPath: "/image/icon_good.png",
      text: "商品中心"
    }, {
      pagePath: "/pages/tabBar/myPage/myPage",
      iconPath: "/image/icon_my_no.png",
      selectedIconPath: "/image/icon_my.png",
      text: "个人中心"
    }]
  },
  attached() {
  },
  methods: {
    switchTab(e) {
      const data = e.currentTarget.dataset
      const url = data.path
      wx.switchTab({url})
      this.setData({
        selected: data.index
      })
    }
  }
})

// index.json
{
  "component": true,
  "usingComponents":{}
}

<!--miniprogram/custom-tab-bar/index.wxml-->
<cover-view class="tab-bar">
  <cover-view class="tab-bar-border"></cover-view>
  <cover-view wx:for="{{list}}" wx:key="index" class="tab-bar-item" data-path="{{item.pagePath}}" data-index="{{index}}" bindtap="switchTab">
    <cover-image src="{{selected === index ? item.selectedIconPath : item.iconPath}}"></cover-image>
    <cover-view style="color: {{selected === index ? selectedColor : color}}">{{item.text}}</cover-view>
  </cover-view>
</cover-view>

/* index.wxss */
.tab-bar {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  height: 48px;
  background: white;
  display: flex;
  padding-bottom: env(safe-area-inset-bottom);
}

.tab-bar-border {
  background-color: rgba(0, 0, 0, 0.33);
  position: absolute;
  left: 0;
  top: 0;
  width: 100%;
  height: 1px;
  transform: scaleY(0.5);
}

.tab-bar-item {
  flex: 1;
  text-align: center;
  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: column;
}

.tab-bar-item cover-image {
  width: 27px;
  height: 27px;
}

.tab-bar-item cover-view {
  font-size: 10px;
}

app.json文件配置

  "tabBar": {
    "custom": true,
    "color": "#7A7E83",
    "selectedColor": "#3cc51f",
    "borderStyle": "black",
    "backgroundColor": "#ffffff",
    "list": [
      {
        "pagePath": "pages/tabBar/home/home",
        "iconPath": "image/icon_home_no.png",
        "selectedIconPath": "image/icon_home.png",
        "text": "首页"
      },
      {
        "pagePath": "pages/tabBar/good/good",
        "iconPath": "image/icon_good_no.png",
        "selectedIconPath": "image/icon_good.png",
        "text": "商品中心"
      },
      {
        "pagePath": "pages/tabBar/myPage/myPage",
        "iconPath": "image/icon_my_no.png",
        "selectedIconPath": "image/icon_my.png",
        "text": "个人中心"
      }
    ]
  },

每个tabbar页面写成组件形式判断

  pageLifetimes: {
    show() {
      if (typeof this.getTabBar === 'function' &&
        this.getTabBar()) {
        this.getTabBar().setData({
          selected: 2
        })
      }
    }
  },