微信小程序 0.5px的border在ios上显示粗细不均匀

用伪类after来写边框

<view style='width: 98rpx; height: 40rpx; color: white; font-size: 18rpx; display: flex; align-items: center; justify-content: center; box-sizing: border-box;  position: relative;'>
   活动说明
   <view class='border'></view> <!-- 这个才是边框 -->
</view>

.border::after { 
  content: '';
  position: absolute;  /* 把父视图设置为relative，方便定位*/
  top: 0;
  left: 0;
  width: 200%;
  height: 200%;
  transform: scale(0.5);
  transform-origin: 0 0;
  box-sizing: border-box;
  border-radius: 40rpx;
  border: 1px solid #fff;
}