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" qq:for="{{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" qq:for="{{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(e) {
    const checked = e.detail.value
    const changed = {}
    for (let 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(e) {
    const checked = e.detail.value
    const changed = {}
    for (let 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;
}