代码片段：https://developers.weixin.qq.com/s/R4H2GmmH7izm

另：<button open-type="share" style="...">分享</button> 这样写才显示

<view class="page-body">

  <view class="page-section page-section-gap">

    <web-view src="https://mp.weixin.qq.com/">

      <cover-view style="position:fixed;right: 0px;bottom:13%;height:80px;width:80px;z-index:999999;background-color:red;">

	<cover-image style="width:100%;height:100%;" src="{{imgSrc}}"></cover-image>

	<button open-type="share" style="position:absolute;top:0;left:0;height:100%;width:100%;opacity:0;z-index:9999999;"></button>

     </cover-view>

   </web-view>

  </view>

</view>