Detailed explanation of WeChat mini program list development

This article mainly shares with you the detailed explanation of the development of WeChat applet list, mainly in the form of code, hoping to help everyone.

1. Knowledge points

(1). List rendering wx:for

tip:wx:for=“array”可以等于参数名，在js中调用
Page({ data:{
array: [{name: '小李'},{ name: '小高'}]}
 })，获取值；也可以直接把wx:for="{{[1, 2, 3]}}"，把值放在上面

1. Use wx:for on the component By binding the control property to an array, the component can be repeatedly rendered using the data of each item in the array.

The subscript variable name of the current item in the default array defaults to index, and the variable name of the current item in the array defaults to item

<view wx:for="{{items}}">
  {{index}}: {{item.message}}
</view>

var app = getApp()
Page({
    data:{
      items: [{
        message: 'foo',
      },{
        message: 'bar'
      }]
    }
})

First of all, in the wxml file, the items in the double braces after wx:for are an array. The elements of the array are as seen in js. Under wx:for, {{index}}:{{item The index in .arry}} is the subscript of the items array, and item.arry is the element in the array, which is "a" and "b".

2. Use wx:for-item to specify the variable name of the current element of the array. Use wx:for-index to specify the variable name of the current subscript of the array:

<view wx:for="{{array}}" wx:for-index="idx" wx:for-item="itemName">
  {{idx}}: {{itemName.name}}
</view>

var app = getApp()
Page({
    data:{
      array: [{
        name: '小李',
      },{
        name: '小高'
      }]
    }
})

3.wx:for can also be nested

<view wx:for="{{[1, 2, 3, 4, 5, 6, 7, 8, 9]}}" wx:for-item="i">
  	<view wx:for="{{[1, 2, 3, 4, 5, 6, 7, 8, 9]}}" wx:for-item="j">
	    <view wx:if="{{i <= j}}">
	       {{i}} * {{j}} = {{i * j}}
	    </view>
 	</view>
</view>

No need for js

(2).block wx:for

is similar to block wx:if, and wx:for can also be used in ea78612b88b3d8fa4b0df3c668292d29 tag to render a structure block containing multiple nodes.

db484d4a41a92a66cda1afdafdb156b6
  89c662c6f8b87e82add978948dc499d2 {{index}}:{{item.name}}de5f4c1163741e920c998275338d29b2
36b196a5d42bcd29e331cb722979f9a6

var app = getApp()
Page({
    data:{
      array: [{
        name: '小李',
      },{
        name: '小高'
      }]
    }
})

(3).wx:key

If the position of the item in the list changes dynamically or new items are added to the list, and you want the items in the list to maintain their own characteristics and status (such as the input content in 0f0306f9b187f2e363126bc29c8b1420, the selected state of 698d939a2c9041f2302734cfeb04788e), you need to use wx:key to specify the items in the list 's unique identifier.

1. String represents a property of the item in the array of the for loop. The value of the property needs to be the only string or number in the list and cannot be changed dynamically.

2. Reserved keyword *this represents the item itself in the for loop. This representation requires the item itself to be a unique string or number, such as:

If wx:key is not provided, a warning will be reported. If you know for sure that the list is static, or if you don't care about its order, you can choose to ignore it.

2. Case

1. User center list

<!--list.wxml-->
<block wx:for="{{userListInfo}}">
	<view class="weui_cell">
		<view class="weui_cell_hd">
			<image src="{{item.icon}}"></image>
		</view>
		<view class="weui_cell_bd">
			<view class="weui_cell_bd_p"> {{item.text}} </view>
		</view>
		<view wx:if="{{item.isunread}}" class="badge">{{item.unreadNum}}</view>
		<view class="with_arrow"></view>
	</view>
</block>

/**list.wxss**/
.weui_cell {
	position: relative;
	display: flex;
	padding: 15px;
	-webkit-box-align: center;
	-ms-flex-align: center;
	align-items: center;
	border-bottom: 1px solid #dadada;
}

.weui_cell_hd {
	display: inline-block;
	width: 20px;
	margin-right: 5px;
}

.weui_cell_hd image {
	width: 100%;
	height: 20px;
	vertical-align: -2px;
}

.weui_cell_bd {
	display: inline-block;
}

.weui_cell_bd_p {
	font-size: 14px;
	color: #939393;
}

.badge {
	position: absolute;
	top: 18px;
	right: 40px;
	width: 15px;
	height: 15px;
	line-height: 15px;
	background: #ff0000;
	color: #fff;
	border-radius: 50%;
	text-align: center;
	font-size: 8px;
}

.with_arrow {
	position: absolute;
	top: 18px;
	right: 15px;
	width: 15px;
	height: 15px;
	background-image: url(../../dist/images/icon-arrowdown.png);
	background-repeat: no-repeat;
	background-size: 100% 100%;
}

//list.js
var app = getApp()
Page( {
  data: {
    userInfo: {},
    userListInfo: [ {
      icon: '../../dist/images/iconfont-dingdan.png',
      text: '我的订单',
      isunread: true,
      unreadNum: 2
    }, {
        icon: '../../dist/images/iconfont-card.png',
        text: '我的代金券',
        isunread: false,
        unreadNum: 2
      }, {
        icon: '../../dist/images/iconfont-icontuan.png',
        text: '我的拼团',
        isunread: true,
        unreadNum: 1
      }, {
        icon: '../../dist/images/iconfont-shouhuodizhi.png',
        text: '收货地址管理'
      }, {
        icon: '../../dist/images/iconfont-kefu.png',
        text: '联系客服'
      }, {
        icon: '../../dist/images/iconfont-help.png',
        text: '常见问题'
      }]
  },
  onLoad: function() {
    var that = this
    //调用应用实例的方法获取全局数据
    app.getUserInfo( function( userInfo ) {
      //更新数据
      	that.setData( {
        	userInfo: userInfo
     	 })
    })
  }
})

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