cover-view嵌套button 调试器正常 真机i5只显示button文本

<map id=“mapId” latitude=“{{lat}}” longitude=“{{lon}}” controls=“{{controls}}” bindcontroltap=“controltap” show-location  >

  <cover-view class=“c_view” >

    <button bindtap=“scan” id=“scan” >测试扫码</button>

  </cover-view>

</map>

#scan{

  position: fixed;

  font-size: 12px;

  height: 30px;

  width: 70px;

  border: 0;

  border-radius:  16px;

}

.c_view{

  height: 30px;

  width: 70px;

  margin: auto;

  margin-top: 548px;

}

#mapId{

  height: 610px;

  width: 375px;  

}