<view>
  <view style="font-size:80rpx">啦啦啦啦啦啦啦啦啦啦啦啦绿绿绿绿绿绿啦啦啦啦啦啦啦啦啦啦啦啦绿绿绿绿绿绿啦啦啦啦啦啦啦啦啦啦啦啦绿绿绿绿绿绿</view>
  <video style="width:100%;height:900rpx;" src="https://www.zyid.com.cn/video/b188a46244d83a4639b5d53565b3c52a.mp4" auto-pause-if-open-native="{{true}}" autoplay='true' bindwaiting="{{true}}" wx:if="{{index == 1}}" direction="0" custom-cache="{{false}}"
    mode="opaque"></video>
  <image style="width:100%;height:900rpx;" src="http://testmr.goldsu.cn/upload/img/1592468253860.jpg" wx:if="{{index == 2}}"></image>
</view>
<view>
  <view style="font-size:80rpx">啦啦啦啦啦啦啦啦啦啦啦啦绿绿绿绿绿绿啦啦啦啦啦啦啦啦啦啦啦啦绿绿绿绿绿绿啦啦啦啦啦啦啦啦啦啦啦啦绿绿绿绿绿绿</view>
  <video style="width:100%;height:900rpx;" src="https://www.zyid.com.cn/video/b188a46244d83a4639b5d53565b3c52a.mp4" auto-pause-if-open-native="{{true}}" autoplay='true' bindwaiting="{{true}}" wx:if="{{index == 2}}" direction="0" custom-cache="{{false}}"
    mode="opaque"></video>
  <image style="width:100%;height:900rpx;" src="http://testmr.goldsu.cn/upload/img/1592468253860.jpg" wx:if="{{index == 1}}"></image>
</view>

js
  data: {
    index:1
  },
  onPageScroll: function (e) {
    if(e.scrollTop>800){
      this.setData({
        index: 2
      })
    }else{
      this.setData({
        index: 1
      })
    }
  },