label

用来改进表单组件的可用性，使用for属性找到对应的id，或者将控件放在该标签下，当点击时，就会触发对应的控件。

for优先级高于内部控件，内部有多个控件的时候默认触发第一个控件。

目前可以绑定的控件有：<button/>, <checkbox/>, <radio/>, <switch/>。

示例代码：

<view class="section section_gap">
<view class="section__title">表单组件在label内</view>
<checkbox-group class="group" bindchange="checkboxChange">
    <view class="label-1" wx:for-items="{{checkboxItems}}">
        <label>
            <checkbox hidden value="{{item.name}}" checked="{{item.checked}}"></checkbox>
            <view class="label-1__icon">
                <view class="label-1__icon-checked" style="opacity:{{item.checked ? 1: 0}}"></view>
            </view>
            <text class="label-1__text">{{item.value}}</text>
        </label>
    </view>
</checkbox-group>
</view>

<view class="section section_gap">
<view class="section__title">label用for标识表单组件</view>
<radio-group class="group" bindchange="radioChange">
    <view class="label-2" wx:for-items="{{radioItems}}">
        <radio id="{{item.name}}" hidden value="{{item.name}}" checked="{{item.checked}}"></radio>
        <view class="label-2__icon">
            <view class="label-2__icon-checked" style="opacity:{{item.checked ? 1: 0}}"></view>
        </view>
        <label class="label-2__text" for="{{item.name}}"><text>{{item.name}}</text></label>
    </view>
</radio-group>
</view>

Page({
  data: {
    checkboxItems: [
      {name: 'USA', value: '美国'},
      {name: 'CHN', value: '中国', checked: 'true'},
      {name: 'BRA', value: '巴西'},
      {name: 'JPN', value: '日本', checked: 'true'},
      {name: 'ENG', value: '英国'},
      {name: 'TUR', value: '法国'},
    ],
    radioItems: [
      {name: 'USA', value: '美国'},
      {name: 'CHN', value: '中国', checked: 'true'},
      {name: 'BRA', value: '巴西'},
      {name: 'JPN', value: '日本'},
      {name: 'ENG', value: '英国'},
      {name: 'TUR', value: '法国'},
    ],
    hidden: false
  },
  checkboxChange: function(e) {
    var checked = e.detail.value
    var changed = {}
    for (var i = 0; i < this.data.checkboxItems.length; i ++) {
      if (checked.indexOf(this.data.checkboxItems[i].name) !== -1) {
        changed['checkboxItems['+i+'].checked'] = true
      } else {
        changed['checkboxItems['+i+'].checked'] = false
      }
    }
    this.setData(changed)
  },
  radioChange: function(e) {
    var checked = e.detail.value
    var changed = {}
    for (var i = 0; i < this.data.radioItems.length; i ++) {
      if (checked.indexOf(this.data.radioItems[i].name) !== -1) {
        changed['radioItems['+i+'].checked'] = true
      } else {
        changed['radioItems['+i+'].checked'] = false
      }
    }
    this.setData(changed)
  }
})

.label-1, .label-2{
    margin-bottom: 15px;
}
.label-1__text, .label-2__text {
    display: inline-block;
    vertical-align: middle;
}

.label-1__icon {
    position: relative;
    margin-right: 10px;
    display: inline-block;
    vertical-align: middle;
    width: 18px;
    height: 18px;
    background: #fcfff4;
}

.label-1__icon-checked {
    position: absolute;
    top: 3px;
    left: 3px;
    width: 12px;
    height: 12px;
    background: #1aad19;
}


.label-2__icon {
    position: relative;
    display: inline-block;
    vertical-align: middle;
    margin-right: 10px;
    width: 18px;
    height: 18px;
    background: #fcfff4;
    border-radius: 50px;
}

.label-2__icon-checked {
    position: absolute;
    left: 3px;
    top: 3px;
    width: 12px;
    height: 12px;
    background: #1aad19;
    border-radius: 50%;
}

.label-4_text{
    text-align: center;
    margin-top: 15px;
}