<template> <div class="transition-container">   <div class="item" v-for="(item, index) in items" :key="index"    draggable="true"    @dragstart="handleDragStart($event, item)"    @dragover.prevent="handleDragOver($event, item)"    @dragenter="handleDragEnter($event, item)"    @dragend="handleDragEnd($event, item)"     @click="chooseNav(item)"    >    <p class="trans-btn">     <span v-if="item.problemId">      <b class="id">        {{item.problemId}}      </b>       {{item.key}}     </span>     <span v-else>       {{item.key}}     </span>     <span>      <i-button v-if="btn" size="small" type="error" style="margin-right: 10px;" @click="deleteItem(item, index)">刪除</i-button>     </span>    </p>   </div> </div></template><script>import './index.less';export default {  name: 'transition',  props: {    dataSource: Array,    btn: Boolean,  },  data() {    return {      items: [],      dragging: null,    };  },  watch: {    dataSource(val) {      this.items = val;    },    dragging(val) {      if (this.dataSource.includes(val)) {        this.dragging = val;      } else {        this.dragging = null;      }    },  },  methods: {    handleDragStart(e, item) {      this.dragging = item;    },    handleDragEnd() {      this.dragging = null;      this.$emit('hasChanged', this.items);    },    // 首先把div變成可以放置的元素，即重寫(xiě)dragenter/dragover    handleDragOver(e) {      e.dataTransfer.dropEffect = 'move';// e.dataTransfer.dropEffect="move";//在dragenter中針對(duì)放置目標(biāo)來(lái)設(shè)置!    },    handleDragEnter(e, item) {      if (this.dragging) {        e.dataTransfer.effectAllowed = 'move';// 為需要移動(dòng)的元素設(shè)置dragstart事件        if (item === this.dragging) {          return;        }        const newItems = [...this.items];        console.log(newItems);        const src = newItems.indexOf(this.dragging);        const dst = newItems.indexOf(item);        newItems.splice(dst, 0, ...newItems.splice(src, 1));        this.items = newItems;      }    },    chooseNav(val) {      this.$emit('selectItem', val);    },    deleteItem(item, index) {      this.$emit('deleteItem', item, index);    },    editor(item, index) {      this.$emit('editorItem', item, index);    },  },};</script>