vue中结合betterScroll制作一个城市选择

###父组件

<template>
    <div>
      <city-header></city-header>
      <city-search></city-search>
      //父组件向子组件传值通过属性绑定的方式
     // @（v-on）接受子组件传递过来的值
      <city-list :citys='citys' :hotCitys='hotCitys' :letter='letter'></city-list>
      <city-alphabet :citys='citys' @change='handleLetterChang'></city-alphabet>
    </div>
</template>

<script>
import axios from 'axios'
import CityHeader from './compontents/Header'
import CitySearch from './compontents/Search'
import CityList from './compontents/List'
import CityAlphabet from './compontents/Alphabet'
export default {
  // 组件注册
  components: {
     CityHeader,
     CitySearch,
     CityList,
     CityAlphabet
  },
  data(){
    return{
      citys:{},
      hotCitys:[],
      letter:''
    }
  },
 mounted () {
    this.getCityInfo()
  },
 // ajax请求
  methods:{
    getCityInfo (){
      axios.get('api/city.json')
      .then(this.handleGetCityInfo)
    },
    handleGetCityInfo (res){
       res = res.data;
       if(res.ret && res.data){
         const data = res.data
         this.citys = data.cities;
         this.hotCitys = data.hotCities
       }
    },
  //处理子组件传递过来的值
    handleLetterChang:function(letter){
      this.letter = letter;
    }
  }
}
</script>  

<style lang="stylus" scoped>

</style>

###城市列表组件

<template>
    <div class='list' ref='warpper'>
        <div>
            <div class="area">
                <div class="title">当前城市 </div>
                <div class="button-list">
                <div class="button-warpper">
                        <div class="button">北京</div>
                </div>
                </div>
            </div>
            <div class="area">
                <div class="title">热门城市 </div>
                <div class="button-list">
                    <template v-for='item of hotCitys'>
                        <div class="button-warpper" :key='item.id'>
                            <div class="button">{{item.name}}</div>
                        </div>  
                    </template>    
              </div>
            </div>
            <template v-for='(item,key) of citys' >    
                <div class="area"  :key='key' :ref='key'>
                    <div class="title"> {{key}} </div>
                    <ul class='area-list' v-for='innerItem of item' :key='innerItem.id'>
                        <li class='area-li'>{{innerItem.name}}</li>
                    </ul>
                </div>
            </template> 
        </div>
    </div>
</template>

<script>
//引入better-scroll 插件
import BScroll from 'better-scroll'
export default{
    name:'CityList',
//接受父组件传递过来的值
    props: {
        hotCitys:Array,
        citys:Object,
        letter:String
    },
    //下拉滚动
    mounted () {
        this.scroll = new BScroll(this.$refs.warpper)
        // console.log(this.$refs.warpper)
    }, 
    watch: {
        letter () { 
            if(this.letter){
                 //点击当前的字母，自动跳转到字母所对应的的地域模块
                const element = this.$refs[this.letter][0];
                this.scroll.scrollToElement(element)
            }
        }
    }
}
</script>  

<style lang="stylus" scoped>
@import '~@styles/varibles.styl';
.list
 overflow hidden
 position absolute
 top 1.78rem
 bottom 0
 left 0
 right 0

.area
 height auto

.title
 line-height .5rem
 background #eeeeee
 padding-left 0.2rem
 font-size .26rem
 text-align left 
 border-bottom .01rem solid #1012

.button-list
 overflow hidden
 padding  .1rem .6rem .1rem .1rem

.button-warpper
 float left
 width:33%

.button
 margin .1rem
 padding .1rem 0
 text-align center 
 border .02rem  solid #cccccc
 border-radius .06rem
 line-height .5rem

.area-li
  line-height .76rem!important
  padding-left .2rem!important
  line-height .76rem
  border-bottom .01rem solid #1012
  text-align left 

</style>

######右边字母定位

<template>
  <ul class="list">
    <li
      v-for="item of letters"
      :key="item"
      :ref="item"
      @click="handleLetterClick"
      @touchstart.prevent="handleTouchStart"
      @touchmove="handleTouchMove"
      @touchend="handleTouchEnd"
    >{{item}}</li>
  </ul>
</template>
<script>
export default {
  name: "Alphabet",
  props: {
    citys: Object
  },
  data() {
    return {
      touchStatus: false,
      startY: 0,
      timer: null
    };
  },
   //当页面挂载完成，startY就不需要重新计算 
  updataed() {
       this.startY = this.$refs["A"][0].getBoundingClientRect().top;
  },
  computed: {
    letters() {
      const letters = [];
      for (let i in this.citys) {
        letters.push(i);
      }
      return letters;
    }
  },
  methods: {
    handleLetterClick: function(e) {
      this.$emit("change", e.target.innerText);
    },
    handleTouchStart() {
      this.touchStatus = true;
    },
    handleTouchMove(e) {
      // const length 字母之间的高度 =   手指划到的高度touchY - 第一个字母 A 距离顶部的高度 startY
      // const index = length /20  总的高度除以20就是分到的等分，也就是当前的字母位置
      // 通过传值的方式将当前的index传递给父组件 
      if (this.touchStatus) {
            if(this.timer){
                clearTimeout(this.timer)
          }
            this.timer = setTimeout(() => {
              const touchY = e.touches[0].clientY;  
              const index = Math.floor((touchY - this.startY ) / 20);
              if (index >= 0 && index < this.letters.length) {
                 this.$emit("change", this.letters[index]);
               }
            },16)
        
      }
    },
    handleTouchEnd() {}
  }
};
</script>
<style lang="stylus" scoped>
@import '~@styles/varibles.styl';

.list {
  display: flex;
  flex-direction: column;
  justify-content: center;
  position: fixed;
  top: 50%;
  right: 0;
  width: 0.4rem;
  transform: translate(2%, -50%);
}

.list li {
  color: $bgColor;
  line-height: 0.4rem;
}
</style>