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
});
}

})