This article will introduce to you several methods to achieve the pull-down to refresh and load more effects in WeChat mini programs. Almost all apps have pull-down refresh and load more effects. I hope you can master them!

【Related learning recommendations: 小program development tutorial】

##Pull down to refresh

There are currently two ways that can be thought of to implement pull-down refresh

1. Call the system’s API. The system provides an API interface for pull-down refresh

2. Monitor scroll-view and customize pull-down refresh. Do you remember that there is a bindscrolltoupper attribute in scroll-view? If you forget, please review the previous article WeChat Mini Program Practical Chapter - E-commerce (2) When scrolling to the top/left, the scrolltoupper event will be triggered, so we can use this attribute to implement the pull-down refresh function.

Both methods are available. The first one is relatively simple and easy to use. After all, some logic systems have already been processed for you. The second one is suitable for small programs that want to customize the pull-down refresh style. We When explaining e-commerce, just use the first one, which is provided by the system. The main purpose is to teach everyone how to use it. Take the homepage as an example

1. Home.json parameter configuration

"enablePullDownRefresh": true

Which page we need to pull down to refresh, configure the above attribute in the xxx.json file corresponding to that page. This attribute literally means You can also know whether pull-down refresh is allowed. Of course, if you don’t want to configure each configuration to allow pull-down refresh, you can directly configure the above attribute in the window of the global variable app.json, so that the entire project allows pull-down refresh. This must be Added because the system does not have the pull-down refresh function by default

2. home.js

  //下拉刷新
  onPullDownRefresh:function()
  {
    wx.showNavigationBarLoading() //在標(biāo)題欄中顯示加載
    
    //模擬加載
    setTimeout(function()
    {
      // complete
      wx.hideNavigationBarLoading() //完成停止加載
      wx.stopPullDownRefresh() //停止下拉刷新
    },1500);
  },

onPullDownRefresh pull-down refresh event Listen, take a look at the code inside, wx.showNavigationBarLoading() and wx.hideNavigationBarLoading(). These two sentences are used to control the display and hiding of the little chrysanthemum. Since we haven’t explained the network request yet, I simulated it. For network loading, use the setTimeout method to write a time delay method. This method can simulate the time consumed by network loading. Also, when the network loading is completed, we need to stop the pull-down refresh wx.stopPullDownRefresh().

This pull-down refresh function has been completed so far, but it is not perfect yet. It is still a bit weird, that is, there is no animation in the pull-down refresh. Is there any~ I also felt strange at the time, the drop-down package in the WeChat envelope How could refresh be like this? Later, I referred to the code written by others and found a small hole. Let's take a look at the effect after I filled in the hole.

How about it? Is it more pleasing to the eye? If you want to know how I added this animation, let me reveal it to you. It’s actually very simple. You only need one sentence of code to configure the following properties in the window in app.json. This is to configure the background color of the entire system. Why do I configure it? The system color will appear in the pull-down refresh. The reason is that the pull-down refresh animation itself has it. However, when we do not configure the background color, the system defaults to white, and the animation is also white, so we cannot see the animation effect. Yes It’s not a bit of a trap, haha~~

"backgroundColor": "#f0145a"

##Load more

There are two ways to load more

• Call the system API

• Listen to scroll-view, bindscrolltolowerSlide to the bottom of the monitor

I Let’s take the first implementation method to explain. The processing method is slightly different from the pull-down refresh, but it is similar. Let’s take the homepage as an example

1, home.js

  //加載更多
  onReachBottom: function () {
    console.log('加載更多')
    setTimeout(() => {
      this.setData({
        isHideLoadMore: true,
        recommends: [
          {
            goodId: 7,
            name: 'OLAY玉蘭油精油沐浴露玫瑰滋養(yǎng)二合一450ml',
            url: 'bill',
            imageurl: 'http://mz.djmall.xmisp.cn/files/product/20161213/148162245074.jpg',
            newprice: "￥36.60",
            oldprice: "￥40.00",
          },
          {
            goodId: 10,
            name: '蘭蔻玫瑰清瀅保濕柔膚水嫩膚水化妝水400ml補(bǔ)水保濕溫和不刺激',
            url: 'bill',
            imageurl: 'http://mz.djmall.xmisp.cn/files/product/20161201/148057937593.jpg',
            newprice: "￥30.00",
            oldprice: "￥80.00",
          }, {
            goodId: 11,
            name: 'Lancome/蘭蔻清瑩柔膚爽膚水/粉水400ml補(bǔ)水保濕玫瑰水化妝水',
            url: 'bill',
            imageurl: 'http://mz.djmall.xmisp.cn/files/product/20161201/148057953326.jpg',
            newprice: "￥30.00",
            oldprice: "￥80.00",
          },
          {
            goodId: 12,
            name: '美國CLINIQUE倩碧黃油無油/特效潤膚露125ml',
            url: 'bill',
            imageurl: 'http://mz.djmall.xmisp.cn/files/product/20161201/14805828016.jpg',
            newprice: "￥239.00",
            oldprice: "￥320.00",
          },
          {
            goodId: 13,
            name: '法國LANCOME蘭蔻柔皙輕透隔離防曬乳霜50ML2017年3月到期',
            url: 'bill',
            imageurl: 'http://mz.djmall.xmisp.cn/files/product/20161201/148058014894.jpg',
            newprice: "￥130.00",
            oldprice: "￥180.00",
          },
        ],
      })
    }, 1000)
  }

onReachBottom The bottom event monitoring provided by the system is the same as the pull-down refresh. We also simulate some data and add a time delay event, isHideLoadMore, a custom value to control the display and hiding of the loading control

2. home.wxml

 <view class="weui-loadmore" hidden="{{isHideLoadMore}}">
    <view class="weui-loading"></view>
    <view class="weui-loadmore__tips">正在加載</view>
  </view>

Add the above code at the bottom of home.wxml. This is to load more controls. Loading more benefits will not be as good as pull-down refresh. The system does not Provides loading more control animations, so we need to make it ourselves

3, home.wxss

/*  加載更多   */
.weui-loading {
  margin: 0 5px;
  width: 20px;
  height: 20px;
  display: inline-block;
  vertical-align: middle;
  -webkit-animation: weuiLoading 1s steps(12, end) infinite;
  animation: weuiLoading 1s steps(12, end) infinite;
  background: transparent url(data:image/svg+xml;base64,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) no-repeat;
  background-size: 100%;
}
.weui-loadmore {
  width: 65%;
  margin: 1.5em auto;
  line-height: 1.6em;
  font-size: 14px;
  text-align: center;
}
.weui-loadmore__tips {
  display: inline-block;
  vertical-align: middle;
}

This is our custom style, the style is very simple, it is a simple loading chrysanthemum , what I want to explain here is setting the background in the weui-loading style, data:image/svg xml;base64What does this mean? Before, we usually set the background and directly add the color. This is another version of the background. How to use it, add a picture, this picture is in base64 format, and is drawn with svg. Of course, you can also directly write the picture path into the url. Okay, let's take a look at the effect!

##Summary

That’s it for today. Pull-down refresh and load more are essential knowledge for front-end programs. Almost all There are pull-down to refresh and load more in the APP, so everyone must master it. The main explanation here is the pull-down to refresh and load more APIs that come with the mini program. You can try to challenge it and use the second method to implement it~

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