微信小程序按钮去除边框线分享页面功能

<button open-type="share" 
style="height:85rpx;width:215rpx;padding:0;background-color:#fff;border-color:#fff;margin-right:10rpx" >
<image style="height:85rpx;width:215rpx;" src='../../../image/share_btn.png'></image>
</button>

button::after{
border: none;
}

 /
   用户点击分享
  /
 onShareAppMessage: function () {
  return { 
   title: '分享',
   desc: '活动描述', 
   path: '/xxx/xxxx?id=' + this.data.id
  } 
 },

 wxml

<button class='niu'>123123</button>

css

niu::after{
　　border:none;
}