网站demo怎么做站长是什么级别
概述
基于小程序开发的列表加载更多例子。
详细
一、前言
基于小程序开发的列表加载更多例子。
二、运行效果
运行效果（演示的小视频，点击播放即可）
三、实现过程
总体思路如何：
1、通过scroll-view组件提供的bindscroll方法监控滚动的时候是否距离底部在40px内，如果小于40px则触发加载更多方法（见完整代码index.js里的bindscroll方法）
2、通过使用发现很多时候服务返回数据太快了，没有加载等待的过程，显的不自然，所以在loadMore方法里通过setTimeout来保证至少有333毫秒的加载时间（见完整代码index.js里的loadMore方法）
3、实际使用中又发现一个问题，上滑到底部会重复触发加载更多方法导致重复的网络请求。通过记录上次加载时间lastRequestTime,保证两次网络请求的间隔大于1秒（见完整代码index.js里的fetchList方法）,这样就能避免重复调用加载更多的问题
备注：demo代码里的网络请求wx.requestTest方法是为了显示效果，所以写了个模拟的请求方法，实际使用可替换为wx.request对接自己项目的服务
具体实现如下：
1、创建小程序，点击下图里框起来的位置，创建小程序
2、在app.js里添加网络模拟方法
let serverData = [];
for(let i = 1; i < 25; i++){serverData.push({id:i, name:i})
}
App({onLaunch: function () {wx.requestTest = ({data:{page,size},success}) => {setTimeout(() => {//模拟网络返回请求let res = {data:{data:{rows: serverData.slice((page - 1) * size, size + (page - 1) * size)},result: true,}}console.log(res)success(res)},1000//模拟网络延迟)}},globalData: {}
})3、增加和pages同层级的components文件夹，在里面创建Loading文件夹，并在下面创建以下文件
//loading.js
Component({data: {},properties: {visible: {//loading效果是否显示type: Boolean,value: false//默认不显示},},
})
//loading.json
{"component": true,//表示是组件"usingComponents": {}
}
//loading.wxss
.loadmore {width: 100%;height: 0rpx;display: flex;align-items: center;justify-content: center;padding-top:24rpx;transition: all 200ms linear;
}
.loadmore.visible {height: 80rpx;
}
.my-loading:after {content: " ";display: block;width: 26px;height: 26px;margin: 1px;border-radius: 50%;border: 2px solid #FFD800;border-color: #fff transparent #FFD800 transparent;animation: lds-dual-ring 1.2s linear infinite;
}
@keyframes lds-dual-ring {0% {transform: rotate(0deg);}100% {transform: rotate(360deg);}
}
//loading.wxml
<view class="loadmore {{visible && 'visible'}}"><view class="my-loading" wx:if="{{visible}}"></view>
</view>4、修改pages/index文件夹下各文件如下
//index.json
{"navigationBarTitleText": "首页","usingComponents": {"loading": "/components/Loading/loading"//引用组件}
}
//index.js
const app = getApp()
let loadingMore = false
let lastScollTop = 0;
let lastRequestTime = 0;
Page({data: {list: [],hasMore: true,//列表是否有数据未加载page: 1,size: 8,//每页8条数据scrollYHeight: 0,//scroll-view高度},bindscroll: function (e) {const { scrollHeight, scrollTop } = e.detail;const { scrollYHeight, hasMore } = this.data;//如果当前没有加载中且列表还有数据未加载，且页面滚动到距离底部40px内if (!loadingMore && hasMore && (scrollHeight - scrollYHeight - scrollTop < 40) && lastScollTop <= scrollTop) {this.loadMore()}lastScollTop = scrollTop},loadMore: function () {const { page, hasMore } = this.data;if (!hasMore || loadingMore) return;loadingMore = truesetTimeout(() => {this.fetchList(page + 1, () => {loadingMore = false;})}, 333)},fetchList: function (page, cb) {let nowRequestTime = (new Date()).getTime();//限制两次网络请求间隔至少1秒if (nowRequestTime - lastRequestTime < 1000) {if (cb) cb();return;}lastRequestTime = nowRequestTime//这里wx.requestTest实际使用时换成wx.request//wx.requestTest定义见app.jswx.requestTest({url: "testUrl",header: {'Authorization': wx.getStorageSync('token')},data: {page,size: this.data.size,},success: (res) => {if (res.data && res.data.result) {let list = res.data.data.rows || [];if (list.length == 0) {this.setData({hasMore: false,page,})} else {this.setData({list: this.data.list.concat(list),hasMore: list.length == this.data.size,page,})}} else {wx.showToast({title: res.data ? res.data.message : "列表加载失败",icon: 'none',duration: 1000})}if (cb) {cb()}},fail: () => {wx.showToast({title: "列表加载失败",icon: 'none',duration: 1000})if (cb) {cb()}}})},onReady: function () {wx.getSystemInfo({success: ({ windowHeight }) => {this.setData({ scrollYHeight: windowHeight })//设置scrill-view组件的高度为屏幕高度}})},onLoad: function () {this.fetchList(1)//加载第一页数据}
})
//index.wxml
<scroll-view scroll-y style="height:{{scrollYHeight}}px" scroll-top="{{scrollTop}}" bindscroll="bindscroll"><viewclass="item"wx:for="{{list}}"wx:key="id"wx:for-index="idx">{{item.name}}</view><loading visible="{{hasMore}}"></loading>
</scroll-view>
//index.css
.item {width: 750rpx;height: 200rpx;font-size: 40rpx;color: black;position: relative;display: flex;align-items: center;justify-content: center;
}
.item::after{content: "";position: absolute;left: 0;right: 0;bottom: 0;border-bottom: 1rpx solid #eeeeee;
}此时运行程序，可查看效果。
整体代码：
//index.js
const app = getApp()
let loadingMore = false
let lastScollTop = 0;
let lastRequestTime = 0;
Page({data: {list: [],hasMore: true,//是否有数据未加载page: 1,size: 8,scrollYHeight: 0,},bindscroll: function (e) {const { scrollHeight, scrollTop } = e.detail;const { scrollYHeight, hasMore } = this.data;//如果当前没有加载中且列表还有数据未加载，且页面滚动到距离底部40px内if (!loadingMore && hasMore && (scrollHeight - scrollYHeight - scrollTop < 40) && lastScollTop <= scrollTop) {this.loadMore()}lastScollTop = scrollTop},loadMore: function () {const { page, hasMore } = this.data;if (!hasMore || loadingMore) return;loadingMore = truesetTimeout(() => {this.fetchList(page + 1, () => {loadingMore = false;})}, 333)},fetchList: function (page, cb) {let nowRequestTime = (new Date()).getTime();if (nowRequestTime - lastRequestTime < 1000) {if (cb) cb();return;}lastRequestTime = nowRequestTime//这里wx.requestTest实际使用时换成wx.request//wx.requestTest定义见app.jswx.requestTest({url: "testUrl",header: {'Authorization': wx.getStorageSync('token')},data: {page,size: this.data.size,},success: (res) => {if (res.data && res.data.result) {let list = res.data.data.rows || [];if (list.length == 0) {if(page == 1){this.setData({hasMore: false,page,list: []})}else {this.setData({hasMore: false,page,})}} else {this.setData({list: this.data.list.concat(list),hasMore: list.length == this.data.size,page,})}} else {wx.showToast({title: res.data ? res.data.message : "列表加载失败",icon: 'none',duration: 1000})}if (cb) {cb()}},fail: () => {wx.showToast({title: "列表加载失败",icon: 'none',duration: 1000})if (cb) {cb()}}})},onReady: function () {const { windowWidth, ratio } = app.globalDatawx.getSystemInfo({success: ({ windowHeight, pixelRatio }) => {this.setData({ scrollYHeight: windowHeight })}})},onLoad: function () {this.fetchList(1)}
})//index.wxml
<scroll-view scroll-y style="height:{{scrollYHeight}}px" scroll-top="{{scrollTop}}" bindscroll="bindscroll"><viewclass="item"wx:for="{{list}}"wx:key="id"wx:for-index="idx">{{item.name}}</view><loading visible="{{hasMore}}"></loading>
</scroll-view>//index.css
.item {width: 750rpx;height: 200rpx;font-size: 40rpx;color: black;position: relative;display: flex;align-items: center;justify-content: center;
}
.item::after{content: "";position: absolute;left: 0;right: 0;bottom: 0;border-bottom: 1rpx solid #eeeeee;
}//app.js
let serverData = [];
for(let i = 1; i < 25; i++){serverData.push({id:i, name:i})
}
App({onLaunch: function () {wx.requestTest = ({data:{page,size},success}) => {setTimeout(() => {//模拟网络返回请求let res = {data:{data:{rows: serverData.slice((page - 1) * size, size + (page - 1) * size)},result: true,}}console.log(res)success(res)},1000//模拟网络延迟)}},globalData: {}
})三、项目结构
四、其他补充
暂时没有