vue3 使用vant-picker封装省市二级联动，设置默认值

怕什么真理无穷，进一步有进一步的欢喜呀，不得不承认的就是，兴趣和擅长是一个良性迭代的循环啊，你擅长某件事情，就会越喜欢它，越喜欢，就越愿意花时间，进而越擅长。所以代码码起来吧哈哈哈

近期用上了vue3，还顺手写了个小需求，用vant-picker封装一个省市的二级联动，并且在从后端接口获取省市的数据，点开弹出框需要展示默认的选项，比如点击广东省-深圳市输入框，弹出的picker级联选择器需要默认广东 -深圳。如下图：

好，那么话不多说，接下来一步一步来实现。
首先，项目中引入vant-ui

import { Popup, Picker } from 'vant'

components: {
    [Picker.name]: Picker,
    [Popup.name]: Popup,
  },

vant官网中，地区联动的形式是这样的

而我的数据格式是这样的

[ {
    "citys": [
      {
        "cityName": "北京市"
      }
    ],
    "provinceName": "北京市"
  },
  {
    "citys": [
      {
        "cityName": "天津市"
      }
    ],
    "provinceName": "天津市"
  },
  {
    "citys": [
      {
        "cityName": "上海市"
      }
    ],
    "provinceName": "上海市"
  },
  {
    "citys": [
      {
        "cityName": "重庆市"
      }
    ],
    "provinceName": "重庆市"
  },]

然后对数据做了处理，处理成官网的形式，这样就可以联动了

 const columnsData = chinaAreaDataType.map((item, index) => {
      const children: { text: string }[] = []
      item.citys.forEach((item) => {
        children.push({
          text: item.cityName,
        })
      })
      return { text: item.provinceName, children }
    })

其中关于一些vue3父子组件的传值就不过多赘述了，有需要可自行查看官方文档
接下来说一说，点开弹出框需要展示默认的选项怎么实现的吧，此处，vant官网给出了一个api，不过没有使用示例，捣鼓了半天。

使用setIndexes设置获取到的索引值，就可以实现点开弹出框需要展示默认的选项了，在onMounted中通过ref去设置相应的索引即可。

onMounted(() => {
      const cityName = toRef(props, 'areaValue').value.split('-')
      const findProvinceName = columnsData.findIndex((value) => value.text === cityName[0])
      const findCityName = columnsData[findProvinceName].children.findIndex((value) => value.text === cityName[1])
      areaPicker.value?.setIndexes([findProvinceName, findCityName])
    })

你以为这样就结束了吗，no no no,还要在popup 中设置lazy-render为false，这样就结束拉~
好吧废话不多说，上子组件代码
子组件代码PickerArea

<template>
  <div class="container">
    <van-popup v-model:show="refShowOverlay" position="bottom" :lazy-render="false" round>
      <van-picker
        ref="areaPicker"
        show-toolbar
        :columns="columnsData"
        value-key="text"
        @change="handleChangeArea"
        @cancel="handleCancelArea"
        @confirm="handleConfirmArea"
      >
        <template v-slot:cancel>
          <div class="icon--button">
            <img src="@/assets/icons/lineCross.svg" />
          </div>
        </template>
        <template v-slot:title>
          <p class="title">{{ title }}</p>
        </template>
        <template v-slot:confirm>
          <div class="icon--button">
            <img src="@/assets/icons/lineHook.svg" />
          </div>
        </template>
      </van-picker>
    </van-popup>
  </div>
</template>

<script lang="ts">
import { defineComponent, ref, toRef, watch, reactive, onMounted } from 'vue'
import { Popup, Picker, Field } from 'vant'
import chinaAreaDataType from './chinaAreaData.json'
export default defineComponent({
  name: 'TasPickerArea',
  components: {
    [Picker.name]: Picker,
    [Popup.name]: Popup,
    [Field.name]: Field,
  },
  props: {
    areaValue: {
      type: String,
      default: '',
    },
    show: {
      type: Boolean,
      default: false,
    },
    showDatePicker: {
      type: Boolean,
      default: false,
    },
    title: {
      type: String,
      default: '请选择地区',
    },
  },
  setup(props, { emit }) {
    const refShowOverlay = ref(false)
    const computedShowOverlay = toRef(props, 'showDatePicker')
    const areaPicker = ref<typeof Picker>()

    const handleCancelArea = () => {
      emit('close', false)
    }
    const columnsData = chinaAreaDataType.map((item, index) => {
      const children: { text: string }[] = []
      item.citys.forEach((item) => {
        children.push({
          text: item.cityName,
        })
      })
      return { text: item.provinceName, children }
    })

    const handleChangeArea = (area: Array<{ text: string }>) => {
      emit('change-area', area)
    }
    const handleConfirmArea = (area: Array<{ text: string }>) => {
      emit('confirm-area', area)
      handleCancelArea()
    }

    watch(computedShowOverlay, (nV) => {
      refShowOverlay.value = nV
    })

    onMounted(() => {
      const cityName = toRef(props, 'areaValue').value.split('-')
      const findProvinceName = columnsData.findIndex((value) => value.text === cityName[0])
      const findCityName = columnsData[findProvinceName].children.findIndex((value) => value.text === cityName[1])
      areaPicker.value?.setIndexes([findProvinceName, findCityName])
    })

    return {
      refShowOverlay,
      areaPicker,
      columnsData,
      handleChangeArea,
      handleCancelArea,
      handleConfirmArea,
    }
  },
})
</script>

<style lang="scss" scoped src="./index.scss" />

父组件代码

<template>
  <div>
    <van-field v-model="areaValue" label="地区" placeholder="请输入地区" @click="handleClickOFF" />
    <tas-picker-china-area
      :show-date-picker="show"
      @close="show = false"
      @confirm-area="handleConfirmArea"
      @change-area="handleChangeArea"
      :areaValue="areaValue"
    />
  </div>
</template>

<script lang="ts">
import { computed, defineComponent, ref, watch, reactive, toRefs } from 'vue'
import { Field } from 'vant'
import { px2remWithUnit } from '@/utils/ui'
import { getThemeVarValue } from '@/config/ui'
import { showDialog } from './components/TasDialog/dialog'
import TasPickerChinaArea from '@/components/TasPickerChinaArea/index.vue'
export default defineComponent({
  name: 'TasButton',
  components: {
    [Field.name]: Field,
    TasPickerChinaArea,
  },
  setup() {
    const show = ref(false)
    const refShowDatePicker = ref(true)
    const areaValue = ref('广东省-深圳市')
    const handleClickOFF = () => {
      show.value = !show.value
    }
    const handleConfirmArea = (area: Array<{ text: string }>) => {
      areaValue.value = `${area[0].text} - ${area[1].text}`
    }
    const handleChangeArea = (area: Array<{ text: string }>) => {}

    return {
      show,
      areaValue,
      refShowDatePicker,
      handleClickOFF,
      handleConfirmArea,
      handleChangeArea,
    }
  },
})
</script>

css代码

.container {
  overflow: hidden;
  &::v-deep(.van-picker-column) {
    font-size: 32px;
  }

  ::v-deep(.van-picker__toolbar) {
    height: auto;
    padding: 30px 45px;
    border-bottom: 1px solid rgba(0, 0, 0, 0.1);
  }
}
.icon--button img {
  width: 52px;
}
.title {
  font-size: 32px;
  font-weight: 500;
  color: #000000;
  line-height: 45px;
}

如有不妥之处，还请大佬指出~