微信小程序实现页面下拉刷新和上拉加载功能详解

<!--pages/WaterFall/WaterFall.wxml--><view style="display:none"> <image wx:for="{{images}}" wx:key="id" id="{{item.id}}" src="{{item.pic}}" bindload="onImageLoad"></image></view><scroll-view scroll-y="true" style="height:{{scrollH}}px" bindscrolltolower="loadImages" bindscrolltoupper="PullDownRefresh"> <view style="width:100%">  <view class="img_item">   <view wx:for="{{col1}}" wx:key="id">    <image src="{{item.pic}}" style="width:100%;height:{{item.height}}px"></image>   </view>  </view>  <view class="img_item">   <view wx:for="{{col2}}" wx:key="id">    <image src="{{item.pic}}" style="width:100%;height:{{item.height}}px"></image>   </view>  </view> </view></scroll-view>

let col1H = 0;let col2H = 0;Page({ data: {  scrollH: 0,  imgWidth: 0,  loadingCount: 0,  images: [],  col1: [],  col2: [] }, onLoad: function () {  wx.getSystemInfo({   success: (res) => {    let ww = res.windowWidth;    let wh = res.windowHeight;    let imgWidth = ww * 0.48;    let scrollH = wh;    this.setData({     scrollH: scrollH,     imgWidth: imgWidth    });    //加载首组图片    this.loadImages();   }  }) }, PullDownRefresh:function(){  console.log("页面下拉2"); },  onShow: function () {   console.log("页面显示"); }, /**  * 生命周期函数--监听页面隐藏  */ onHide: function () {  console.log("页面隐藏"); }, /**  * 用户点击右上角分享  */ onShareAppMessage: function () {  console.log("点击分享"); }, onImageLoad: function (e) {  let imageId = e.currentTarget.id;  let oImgW = e.detail.width;     //图片原始宽度  let oImgH = e.detail.height;    //图片原始高度  let imgWidth = this.data.imgWidth; //图片设置的宽度  let scale = imgWidth / oImgW;    //比例计算  let imgHeight = oImgH * scale;   //自适应高度  let images = this.data.images;  let imageObj = null;  for (let i = 0; i < images.length; i++) {   let img = images[i];   if (img.id === imageId) {    imageObj = img;    break;   }  }  imageObj.height = imgHeight;  let loadingCount = this.data.loadingCount - 1;  let col1 = this.data.col1;  let col2 = this.data.col2;  //判断当前图片添加到左列还是右列  if (col1H <= col2H) {   col1H += imgHeight;   col1.push(imageObj);  } else {   col2H += imgHeight;   col2.push(imageObj);  }  let data = {   loadingCount: loadingCount,   col1: col1,   col2: col2  };  //当前这组图片已加载完毕，则清空图片临时加载区域的内容  if (!loadingCount) {   data.images = [];  }  this.setData(data); }, loadImages: function () {  let images = [   { pic: "../../images/1.png", height: 0 },   { pic: "../../images/2.png", height: 0 },   { pic: "../../images/3.png", height: 0 },   { pic: "../../images/4.png", height: 0 },   { pic: "../../images/5.png", height: 0 },   { pic: "../../images/6.png", height: 0 },   { pic: "../../images/7.png", height: 0 },   { pic: "../../images/8.png", height: 0 },   { pic: "../../images/9.png", height: 0 },   { pic: "../../images/10.png", height: 0 },   { pic: "../../images/11.png", height: 0 },   { pic: "../../images/12.png", height: 0 },   { pic: "../../images/13.png", height: 0 },   { pic: "../../images/14.png", height: 0 }  ];  console.log("dasddasd" + images);  let baseId = "img-" + (+new Date());  for (let i = 0; i < images.length; i++) {   images[i].id = baseId + "-" + i;  }  this.setData({   loadingCount: images.length,   images: images  }); }})