微信小程序echarts层级过高

项目中由于需求，底部的tab导航栏是本身写的，在开发者工具中一切正常；可是在真机上页面滑动时，echarts的层级比tab高，调过二者的z-index后仍然如此。

通过查找后发现cover-view和cover-image替换tab的view后，能够解决以上的问题。

<!--底部公共tabBar-->
<cover-view class="tabbar-con">
    <cover-view class="{{villageIs?'nav-btn-hover':'nav-btn'}}" bindtap="onGetVillage">
                <cover-image class='icon_village_after icon' wx:if="{{villageIs}}" src=''></cover-image>
                <cover-image class='icon_village_before icon' wx:else src=''></cover-image>
        <cover-view>小区</cover-view>
    </cover-view>
    <cover-view class="{{shopcarIs?'nav-btn-hover':'nav-btn'}}" bindtap="onGetShopcar">
                <cover-image class='icon_shop_after icon' wx:if="{{shopcarIs}}" src=''></cover-image>
        <cover-image class='icon_shop_before icon' wx:else src=''></cover-image>
        <cover-view>购物车</cover-view>
    </cover-view>
    <cover-view class="{{newsIs?'nav-btn-hover':'nav-btn'}}" bindtap="onGetNews">
                <cover-image class='icon_news_after icon' wx:if="{{newsIs}}" src=''></cover-image>
        <cover-image class='icon_news_before icon' wx:else src=''></cover-image>
        <cover-view>新闻</cover-view>
    </cover-view>
    <cover-view class="{{mineIs?'nav-btn-hover':'nav-btn'}}" bindtap="onGetMine">
            <cover-image class='icon_mine_after icon' wx:if="{{mineIs}}" src=''></cover-image>
      <cover-image class='icon_mine_before icon' wx:else src=''></cover-image>
      <cover-view>个人</cover-view>
    </cover-view>
</cover-view>