乐趣区

vue递归组件实战之简单树形控件

jiezi

1、递归组件 - 简单树形控件预览及问题

在编写树形组件时遇到的问题：

  • 组件如何才能递归调用？
  • 递归组件点击事件如何传递？

2、树形控件基本结构及样式

<template>
  <ul class="vue-tree">
    <li class="tree-item">
      <div class="tree-content"><!-- 节点内容 -->
        <div class="expand-arrow"></div><!-- 展开或收缩节点按钮 -->
        <div class="tree-label"> 小学 </div><!-- 节点文本内容 -->
      </div>
      <ul class="sub-tree"><!-- 子节点 -->
        <li class="tree-item expand">
          <div class="tree-content">
            <div class="expand-arrow"></div>
            <div class="tree-label"> 语文 </div>
          </div>
        </li>
        <li class="tree-item">
          <div class="tree-content">
            <div class="expand-arrow"></div>
            <div class="tree-label"> 数学 </div>
          </div>
        </li>
      </ul>
    </li>
  </ul>
</template>

<style lang="stylus">
.vue-tree{
  list-style: none;
  padding: 0;
  margin: 0;
  .tree-item{
    cursor: pointer;
    transition: background-color .2s;
    .tree-content{
      position: relative;
      padding-left: 28px;
      &:hover{background-color: #f0f7ff;}
    }
    .expand-arrow{
      position: absolute;
      top: 0;
      left: 0;
      width: 28px;
      height: 28px;
      cursor: pointer;
      &::after{
        position: absolute;
        top: 50%;
        left: 50%;
        display: block;
        content: ' ';
        border-width: 5px;
        border-style: solid;
        border-color: transparent;
        border-left-color: #ccc;
        margin: -5px 0 0 -2.5px;
        transition: all .2s;
      }
    }
    &.expand{
      &>.tree-content{
        background-color: #f0f7ff;
        &>.expand-arrow{
          &::after{transform: rotate(90deg);
            margin: -2.5px 0 0 -5px;
          }
        }
      }
    }
    .tree-label{
      height: 28px;
      line-height: 28px;
      font-size: 14px;
    }
    .sub-tree{
      display: none;
      list-style: none;
      padding: 0 0 0 28px;
      margin: 0;
    }
    &.expand>.sub-tree{display: block;}
    &.no-child{
      &>.tree-content{
        &>.expand-arrow{display: none;}
      }
    }
  }
}
</style>

3、组件目录及数据结构

目录结构
vue-tree

  • VueTree.vue 树形控件父组件
  • TreeItem.vue 树形控件递归组件

树形控件数据结构

let treeData = [
  {
    text: "一级", // 显示的文字
    expand: false, // 默认是否展开
    children: [ // 子节点
      {
        text: "一级 -1",
        expand: false,
      },
      {
        text: "一级 -2",
        expand: false,
        children: [
          {
            text: "一级 -2-1",
            expand: false,
          },
          {
            text: "一级 -2-2",
            expand: false,
          }
        ]
      }
    ]
  }
];

3.1、TreeItem.vue 代码

<template>
  <li class="tree-item" :class="{expand: isExpand,'no-child': !treeItemData.children || treeItemData.children.length  === 0}">
    <div class="tree-content" @click="_clickEvent">
      <div class="expand-arrow" @click.stop="expandTree()"></div>
      <div class="tree-label">{{treeItemData.text}}</div>
    </div>
    <ul class="sub-tree" v-if="treeItemData.children && treeItemData.children.length > 0">
      <!--TreeItem 组件中调用 TreeItem 组件 -->
      <TreeItem
        v-for="item in treeItemData.children"
        :tree-item-data="item"
        :key="uuid()"
        :tree-click-event="treeClickEvent"></TreeItem>
    </ul>
  </li>
</template>

<script>
  export default {
    name: "TreeItem",
    props: {
      treeItemData: {
        type: Object,
        default(){return {};
        }
      },
      // 节点点击事件
      treeClickEvent: {
        type: Function,
        default() {return function () {};}
      }
    },
    data(){
      return {
        // 节点是否展开
        isExpand: this.treeItemData.expand || false
      }
    },
    methods: {
      // 展开 / 收缩
      expandTree(flag){if(!this.treeItemData.children || this.treeItemData.children.length === 0){return;}
        if(typeof flag === 'undefined'){flag = !this.isExpand;}else{flag = !!flag;}
        this.isExpand = flag;
      },
      // 创建一个唯一 id
      uuid(){let str = Math.random().toString(32);
        str = str.substr(2);
        return str;
      },
      // 节点点击事件
      _clickEvent(){
        // 如果有传递事件函数，则调用事件函数并传递当前节点数据及组件
        if(this.treeClickEvent && typeof this.treeClickEvent === 'function'){this.treeClickEvent(this.treeItemData, this);
        }
      }
    }
  }
</script>

3.1.1、解决 组件如何才能递归调用？ 问题

在组件模板内调用自身 必须明确定义组件的 name 属性 ，并且递归调用时组件名称就是 name 属性。如在TreeItem.vue 组件中组件的 name 名称为 ’TreeItem’，那么在 template 中调用时组件名称就必须是 <TreeItem>。
当然也可以全局注册组件，具体可以查看 vue 官方文档 递归组件

3.1.2、解决 递归组件点击事件如何传递？ 问题

我这里的解决方案是使用 props 将事件函数传递进来，在点击节点的时候调用事件函数，并把相应的数据传递进去。
之前也尝试过使用 $emit 的形式并把数据传递过去，由于是递归组件，这样一直$emit，到最外层时传递的数据就变了，比如传递是第 3 层节点的数据，到最后执行时数据就变成第 1 层节点的数据了

4、VueTree.vue 组件

<template>
  <ul class="vue-tree">
    <TreeItem
        v-for="(item, index) in treeData"
        :key="index"
        :treeItemData="item"
        :tree-click-event="treeClickEvent"></TreeItem>
  </ul>
</template>

<script>
  import TreeItem from "./TreeItem";
  export default {
    name: "VueTreeMenu",
    components: {TreeItem},
    props: {
     // 树形控件数据
      treeData: {
        type: Array,
        default(){return [];
        }
      },
      // 节点点击事件
      treeClickEvent: {
        type: Function,
        default() {return function () {};}
      }
    }
  }
</script>

<style lang="stylus">
.vue-tree{
  list-style: none;
  padding: 0;
  margin: 0;
  .tree-item{
    cursor: pointer;
    transition: background-color .2s;
    .tree-content{
      position: relative;
      padding-left: 28px;
      &:hover{background-color: #f0f7ff;}
    }
    .expand-arrow{
      position: absolute;
      top: 0;
      left: 0;
      width: 28px;
      height: 28px;
      cursor: pointer;
      &::after{
        position: absolute;
        top: 50%;
        left: 50%;
        display: block;
        content: ' ';
        border-width: 5px;
        border-style: solid;
        border-color: transparent;
        border-left-color: #ccc;
        margin: -5px 0 0 -2.5px;
        transition: all .2s;
      }
    }
    &.expand{
      &>.tree-content{
        background-color: #f0f7ff;
        &>.expand-arrow{
          &::after{transform: rotate(90deg);
            margin: -2.5px 0 0 -5px;
          }
        }
      }
    }
    .tree-label{
      height: 28px;
      line-height: 28px;
      font-size: 14px;
    }
    .sub-tree{
      display: none;
      list-style: none;
      padding: 0 0 0 28px;
      margin: 0;
    }
    &.expand>.sub-tree{display: block;}
    &.no-child{
      &>.tree-content{
        /*padding-left: 0;*/
        &>.expand-arrow{display: none;}
      }
    }
  }
}
</style>

5、使用树形组件

<template>
  <div class="app" id="app">
    <VueTree :tree-data="treeData2" :tree-click-event="treeClickEvent"></VueTree>
  </div>
</template>

<script>
import VueTree from "./components/vue-tree/VueTree";

export default {
  name: 'app',
  data(){
    return {
      treeData2: [
        {
          text: "一级", // 显示的文字
          expand: false, // 默认是否展开
          children: [
            {
              text: "二级 -1",
              expand: false,
            },
            {
              text: "二级 -2",
              expand: false,
              children: [
                {
                  text: "三级 -1",
                  expand: false,
                },
                {
                  text: "三级 -2",
                  expand: false,
                  children: [
                    {
                      text: "四级 -1",
                      expand: false,
                    }
                  ]
                }
              ]
            }
          ]
        },
        {
          text: "一级 -2",
          expand: false
        }
      ]
    }
  },
  methods: {treeClickEvent(item, treeItem){console.log(item);
    }
  },
  components: {VueTree}
}
</script>
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