cover-image做图片轮播时，在真机上图片无法轮播，开发工具正常

<view class="carousel" >
    <swiper  indicator-dots='true' autoplay='true' interval='3000' duration='500' circular="true" >
      <block wx:for="{{bnrUrl}}" wx:key="key" wx:for-item="titleUrl">
        <swiper-item>
         <cover-image class="titleImage" src="{{titleUrl}}"  ></cover-image>
          <!-- <image src='{{titleUrl.path}}?app=app' class='u-img-slide' mode='aspectFill'></image> -->
        </swiper-item>
      </block>
    </swiper>
  </view>