WXML： 

<swiper indicator-dots="{{indicatorDots}}"  style="height:{{height}}px"

      class="swipe_container"     autoplay="{{autoplay}}" interval="{{interval}}" duration="{{duration}}" circular="true">  
         <block wx:for="{{imgArray}}">  
           <swiper-item>  
               <image src="{{item.filePath+item.fileName}}" mode="widthFix" class="slide-image" bindload="setContainerHeight"/>  
           </swiper-item>  

         </block>  

 </swiper>  
 

WXSS：

.swipe_container{
  width:100%;

}
.slide-image{
  width:100%;
}

JS：

Page({
  data: {
    imgArray:[],
    indicatorDots: true,
    autoplay: true,
    interval: 5000,
    duration: 1000,
    height:0
  },
  setContainerHeight:function(e){
    var imgWidth=e.detail.width;   //圖片的原始寬度
    var imgHeight = e.detail.height; //圖片的原始高度
    var sysInfo = wx.getSystemInfoSync();//同步獲取裝置寬度
    var screenWidth=sysInfo.screenWidth; //獲取螢幕的寬度
    var scale = screenWidth / imgWidth;   //獲取螢幕和原圖的比例
    this.setData({
      height:imgHeight*scale
    })
  },
})