解决vux 中popup 组件Mask 遮罩在最上层的问题

<template>
 <div id='discounts' :class="{'fixed-touch':showDetail}">
    <button @click="showDetail=true">弹出popup组件</button>
   // 遮罩层
    <div class="overlayer" @touchmove.prevent v-show="showDetail" @click="showDetail=false"></div>
   // 这里注意下，要把popup组件的遮罩显示设置为false
    <popup v-model="showDetail" position="bottom" max-height="80%" should-rerender-on-show :show-mask="false">
      <div class="popup-style">弹出框内容</div>
    </popup>
  </div>
</template>

<script>
import { Popup } from 'vux'
export default {
 data () {
  return {
    showDetail: false
    }
  },
 components: {
  Popup
 }
}
</script>

<style>
.fixed-touch {position: fixed;}
.overlayer{
  position:fixed;
  left:0;
  top:0;
  width:100%;
  height:100%;
  z-index: 500;
  background-color: #000;
  opacity: .5;
 }
</style>