大体思路：通过获取原图片的宽高得出宽高比例，结合当前屏幕的宽度算出新高度赋值给swiper。
index.js
data: {
imgUrls: [
'http://www.aliddmall.com/images/app_banners/1.jpg',
'http://www.aliddmall.com/images/app_banners/2.jpg'
],
indicatorDots: true,
autoplay: true,
interval: 3000,
duration: 500,
Height: "" //这是swiper要动态设置的高度属性
},
index.wxml
<swiper indicator-dots="{{indicatorDots}}"
autoplay="{{autoplay}}" interval="{{interval}}" duration="{{duration}}" style='height:{{Height}}'>
<block wx:for="{{imgUrls}}" wx:key="unique">
<swiper-item>
<image src="{{item}}" class="slide-image" mode="widthFix" bindload='imgHeight' />
</swiper-item>
</block>
</swiper>
