Detailed explanation of WeChat applet implementation of pull-down loading and pull-up refresh

onPullDownRefresh(){
　　console.log('--------下拉刷新-------')
　　wx.showNavigationBarLoading() //在标题栏中显示加载
 
　　wx.request({
          url: 'https://URL',
          data: {},
          method: 'GET',
         // OPTIONS, GET, HEAD, POST, PUT, DELETE, TRACE, CONNECT
          // header: {}, // 设置请求的 header
          success: function(res){
            // success
          },
          fail: function() {
            // fail
          },
          complete: function() {
            // complete
            wx.hideNavigationBarLoading() //完成停止加载
            wx.stopPullDownRefresh() //停止下拉刷新
          }
    })

index.wxml

<!--index.wxml-->
<view class="container" style="padding:0rpx">
  <!--垂直滚动，这里必须设置高度-->
    <scroll-view scroll-top="{{scrollTop}}" scroll-y="true" style="height:{{scrollHeight}}px;" 
        class="list" bindscrolltolower="bindDownLoad" bindscrolltoupper="topLoad"  bindscroll="scroll">
        <view class="item" wx:for="{{list}}">
            <image class="img" src="{{item.pic_url}}"></image>
            <view class="text">
                <text class="title">{{item.name}}</text>
                <text class="description">{{item.short_description}}</text>
            </view>
        </view>
    </scroll-view>
    <view class="body-view">
        <loading hidden="{{hidden}}" bindchange="loadingChange">
            加载中...
        </loading>
    </view>
</view>

var url = "http://www.imooc.com/course/ajaxlist";
var page =0;
var page_size = 5;
var sort = "last";
var is_easy = 0;
var lange_id = 0;
var pos_id = 0;
var unlearn = 0;


// 请求数据
var loadMore = function(that){
    that.setData({
        hidden:false
    });
    wx.request({
        url:url,
        data:{
            page : page,
            page_size : page_size,
            sort : sort,
            is_easy : is_easy,
            lange_id : lange_id,
            pos_id : pos_id,
            unlearn : unlearn
        },
        success:function(res){
            //console.info(that.data.list);
            var list = that.data.list;
            for(var i = 0; i < res.data.list.length; i++){
                list.push(res.data.list[i]);
            }
            that.setData({
                list : list
            });
            page ++;
            that.setData({
                hidden:true
            });
        }
    });
}
Page({
  data:{
    hidden:true,
    list:[],
    scrollTop : 0,
    scrollHeight:0
  },
  onLoad:function(){
    //   这里要注意，微信的scroll-view必须要设置高度才能监听滚动事件，所以，需要在页面的onLoad事件中给scroll-view的高度赋值
      var that = this;
      wx.getSystemInfo({
          success:function(res){
              that.setData({
                  scrollHeight:res.windowHeight
              });
          }
      });
       loadMore(that);
  },
  //页面滑动到底部
  bindDownLoad:function(){   
      var that = this;
      loadMore(that);
      console.log("lower");
  },
  scroll:function(event){
    //该方法绑定了页面滚动时的事件，我这里记录了当前的position.y的值,为了请求数据之后把页面定位到这里来。
     this.setData({
         scrollTop : event.detail.scrollTop
     });
  },
  topLoad:function(event){
    //   该方法绑定了页面滑动到顶部的事件，然后做上拉刷新
      page = 0;
      this.setData({
          list : [],
          scrollTop : 0
      });
      loadMore(this);
      console.log("lower");
  }
})

/**index.wxss**/

.userinfo {
  display: flex;
  flex-direction: column;
  align-items: center;
}

.userinfo-avatar {
  width: 128rpx;
  height: 128rpx;
  margin: 20rpx;
  border-radius: 50%;
}

.userinfo-nickname {
  color: #aaa;
}

.usermotto {
  margin-top: 200px;
}

/**/

scroll-view {
  width: 100%;
}

.item {
  width: 90%;
  height: 300rpx;
  margin: 20rpx auto;
  background: brown;
  overflow: hidden;
}

.item .img {
  width: 430rpx;
  margin-right: 20rpx;
  float: left;
}

.title {
  font-size: 30rpx;
  display: block;
  margin: 30rpx auto;
}

.description {
  font-size: 26rpx;
  line-height: 15rpx;
}