微信小程序列表加载更多

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

image.png

image.png

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 = true
    setTimeout(
      () => {
        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.js
    wx.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">
    <view
      class="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 = true
    setTimeout(
      () => {
        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.js
    wx.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.globalData
    wx.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">
    <view
      class="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

WX20180719-134632@2x.png

 

四、其他补充

暂时没有

注:本文著作权归作者,由demo大师发表,拒绝转载,转载需要作者授权

posted on 2018-08-10 09:22  demo例子集  阅读(12906)  评论(0编辑  收藏  举报

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