微信小程序实现页面下拉刷新和上拉加载

微信小程序实现页面下拉刷新和上拉加载

        web手机端或App中经常会有下拉刷新，上拉加载这些功能。

       微信小程序中如何实现下拉刷新，上拉加载的功能。

       实现思路：

       1.监听界面的下拉刷新事件和上拉加载事件

bindscrolltolower 监听上拉加载

bindscrolltoupper 监听下拉刷新

       2.下拉刷新时清空数据列表，并重新请求数据进行界面展示。

       3.上拉加载增量请求数据，增量增加数据列表，增量界面展示

     效果图：

      实现代码：

     WaterFall.wxml:

<!--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>

WaterFall.js：

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    });  }})