<el-tree 
        class="treeitems"
        :data="data"
        node-key="id"
        :props="defaultProps" 
        :load="loadNode"
        lazy
        :default-expanded-keys="[0]"
        @node-click="handleNodeClick"
        draggable
        :allow-drop="allowDrop"
        :allow-drag="allowDrag"
         @node-drop="handleDrop"
        ref="tree"
      >
      <span class="custom-tree-node" slot-scope="{ node, data }">
        <span>{{ node.label }}</span>
        <span>
          <i @click="() => append(node,data)" class="el-icon-plus"></i><!--增加分组-->
          <!-- 根节点不需要删除和重命名 -->
          <i v-if="data.id !== 0" @click="() => deletes(node,data)" class="el-icon-delete"></i><!--删除分组-->
          <i v-if="data.id !== 0" @click="() => rename(node,data)" class="el-icon-edit"></i><!--重命名分组-->
        </span>
      </span>
     </el-tree>

data() {
   return {
    filterText: '',
    data: [{
      id:0,
      label: '中国',
      
    }],
    children: [{
        id:1,
        label: '北京',
        children: [{
          id:11,
          label: '通州'
        }]
      },
      {  
        id:2,
        label: '上海',
        leaf: true,
      },
      {  
        id:3,
        label: '山西',
        children:[{
          id: 13,
          label: '太原'
        },{
          id: 14,
          label: '阳泉'
        }]
      },{
        id:4,
        label: '黑龙江',
        children: [{
          id:12,
          label: '哈尔滨'
        }]
      }],
    defaultProps: {
     children: 'children',
     label: 'label',
     isLeaf: 'leaf'
    }
   };

 //点重命名事件
 append(node,data) {
      console.log(node,data,'增加')
      this.$prompt('节点名字', '增加节点', {
        confirmButtonText: '确定',
        cancelButtonText: '取消',
        inputPattern: /^[\u4e00-\u9fa5]{0,}$/,//匹配全中文
        inputErrorMessage: '请输入中文'//不符合正则匹配的提示语句
        }).then(({ value }) => {
          //可以在这里发请求，http是我模拟的一个虚假的封装好的axios请求,()可写请求参数
          http().then((data)=>{
            this.$message({
              type: 'success',
              message: '修改成功'
            }); 
            //请求成功需局部刷新该节点，调用方法,把节点信息node传入
            this.partialRefresh(node)
          })
          //请求失败
          .catch(()=>{
            this.$message({
              type: 'info',
              message: '修改失败'
            }); 
          })
        }).catch(() => {
          this.$message({
            type: 'info',
            message: '取消修改'
          });    
      });
    },
    //实现局部刷新，在点击弹窗处调用的
    partialRefreshpartialRefresh(node){
      //设置loaded为false；模拟一次节点展开事件，加载重命名后的新数据；
      node.loaded = false;
      node.expand(); 
      //新建子节点是刷新一次本节点的展开请求，而重命名和删除则需要刷新父级节点的的展开事件，
      //可以设置node.parent.loaded = false;node.parent.expand();
    },

 //懒加载
    loadNode(node, resolve){
      if (node.level === 0) {
        //本地的数据，一个承载中国字样的数组；
        return resolve(this.data);
      }
      else if(node.level === 1){
        //现在为模拟数据；
        //有真实数据，在resolve中放置请求回来的数据即可。
        //else同样也是。我这里是区分了两种请求方式。
        return resolve(this.children)
      }
      else{
        return resolve([])
      }
    },

 //拖拽==>拖拽时判定目标节点能否被放置
    allowDrop(draggingNode, dropNode, type){
      //参数：被拖拽节点，要拖拽到的位置
      //因为根目录是我本地写死的，不能有同级，所以我设置凡是拖拽到的level===1都存放到根节点的下面；
      if(dropNode.level===1){
        return type == 'inner';
      }
      else {
        return true;
      }
    },
    //拖拽==>判断节点能否被拖拽
    allowDrag(draggingNode){
     //第一级节点不允许拖拽
      return draggingNode.level !== 1;
    },

//拖拽==>拖拽时判定目标节点能否被放置
    //后更改为只能同级拖拽
    allowDrop(draggingNode, dropNode, type) {
      if (draggingNode.level === dropNode.level) {
        if (draggingNode.data.parentId === dropNode.data.parentId) {
          return type === 'prev' || type === 'next'
        }
      } else {
        // 不同级不允许拖拽
        return false
      }
    },
    //拖拽==>判断节点能否被拖拽
    allowDrag(draggingNode) {
      return draggingNode.level !== 1;
    },
    //拖拽成功完成时触发的事件，在这里可以将节点拖拽后的顺序返给后端
    handleDrop(node,data,type,event){
      let arr=[];
      //data为拖拽后节点信息，找到它的父级，在从父级找子集
      let child = data.parent.childNodes;
      for(var key in child){
        arr.push({id:child[key].data.id})
      }
      //转为JSON字符串发请求带走信息
      idSort(JSON.stringify(arr))
    }

<template>
 <div>
  <div class="exam_structure">
   <el-input
    placeholder="输入关键字进行过滤"
    v-model="filterText">
   </el-input>
 
 
   <el-button type="primary" size="small" class="add_new_question" @click="add_new_question"><i></i>添加父节点</el-button>
 
  </div>
 
  <div class="question_info_lists">
 
   <el-tree ref="tree" :key="tree_key" :data="treeData" node-key="id" :render-content="renderContent"
        :expand-on-click-node="false" :default-expanded-keys="defaultExpand" show-checkbox
        :filter-node-method="filterNode"></el-tree> 
 
   <el-row class="add_question" v-show="add_question_flag">
 
    <el-col :span="12">
 
     <el-input v-model="new_question_name" placeholder="请输入大题名称"></el-input>
 
    </el-col>
 
    <el-col :span="12">
 
     <el-button size="mini" class="btn_sure" @click.stop="add_question_sure">确定</el-button>
 
     <el-button size="mini" class="btn_cancel" @click.stop="add_question_cancel">取消</el-button>
 
    </el-col>
 
   </el-row>
 
  </div>
 </div>
</template>
 
<script>
 export default {
  name: "tree1",
 
  watch: {
   filterText(val) {
    this.$refs.tree.filter(val);
   }
  }, 
 
  methods: {
   filterNode(value, data) {
    if (!value) return true;
    return data.label.indexOf(value) !== -1;
   },
// 添加新大题
 
   add_new_question() { 
    this.add_question_flag = true 
   },
 
   add_question_sure() {  //确定
 
    const nodeObj = {id: '', label: this.new_question_name, isEdit: false, children: []}
    this.treeData.push(nodeObj)
    this.add_question_flag = false
 
   },
 
   add_question_cancel() {  //取消 
    this.add_question_flag = false 
    this.new_question_name = '' 
   },
 
   //   增加
   append(store, node, data) {
    var maxid = '20'
    //新增数据
    const nodeapp = {id: ++maxid, label: '增加节点', isEdit: false, children: []}
    data.children.push(nodeapp)
    if (!node.expanded) {
     node.expanded = true
    }
    const parent = node.parent
    const children = parent.data
    const cIndex = children.findIndex(d => d.id === data.id)
    const tempChildrenNodex2 = children[cIndex] //拿到被添加的上一级
    console.log(tempChildrenNodex2.children[cIndex - 1])
   },
 
// 修改
 
   nodeEdit(ev, store, data) { 
    data.isEdit = true 
    this.$nextTick(() => { 
     const $input = ev.target.parentNode.parentNode.querySelector('input') || ev.target.parentElement.parentElement.querySelector('input') 
 
     !$input "text" value={data.label} on-blur={ev => this.edit_sure(ev, data)}/> 
    } else { 
     return <span className="node_labe">{data.label}</span> 
    } 
   },
 
// 结构树操作group node, 
   renderContent(h, {node, data, store}) { 
    return ( 
     <span> 
<span class="el-icon-document"> 
{this.showOrEdit(data)} 
</span> 
<div class="tree_node_op" style=" float: right"> 
<i class="el-icon-edit" on-click={(ev) => this.nodeEdit(ev, store, data)}></i> 
<i class="el-icon-delete" on-click={() => this.nodeDelete(node, data)}></i> 
<i class="el-icon-upload2" on-click={() => this.nodeUp(node, data)}></i> 
<i class="el-icon-download" on-click={() => this.nodeDown(store, node, data)}></i>
<i class="el-icon-plus" on-click={() => this.append(store, node, data)}></i>
 
</div> 
</span>) 
   } 
  }
  , data() { 
   return {
    filterText: '',
    treeData: [{
 
     id: 1, 
     label: '一级 1', 
     isEdit: false, 
     children: [{ 
      id: 4, 
      label: '二级 1-1', 
      isEdit: false, 
      children: [{id: 9, label: '三级 1-1-1', isEdit: false, children: []}, {
       id: 10,
       label: '三级 1-1-2',
       isEdit: false,
       children: []
      }, {
       id: 11,
       label: '三级 1-1-3',
       isEdit: false,
    children: []
      }] 
     },
 
      { 
       id: 12, 
       label: '二级 1-2', 
       isEdit: false, 
       children: [] 
      },
 
      { 
       id: 13, 
       label: '二级 1-3', 
       isEdit: false, 
       children: [] 
      }] 
    },
 
     { 
      id: 2, 
      label: '一级 2', 
      isEdit: false,
       children: [{id: 5, label: '二级 2-1', isEdit: false, children: []}, {
       id: 6,
       label: '二级 2-2',
       isEdit: false,
       children: []
      }] 
     },
 
     { 
      id: 3, 
      label: '一级 3', 
      isEdit: false, 
      children: [
       {id: 7, label: '二级 3-1', isEdit: false, children: []},
       {
       id: 8,
       label: '二级 3-2',
       isEdit: false,
       children: []
      }] 
     }],
 
    add_question_flag: false, 
    new_question_name: '', 
    tree_key: 0, 
    defaultExpand: [] 
   } 
  }, 
 }
</script> 
<style scoped> 
</style>