问题描述

在开发中遇到一个需求，即实现table列的拖拽，但是调研发现，大部分是基于sorttable.js这个包实现的，但是通过实际应用，发现sorttable.js用在操作element table 组件中并不是很舒服，总会莫名其妙的冒出一些异常bug，于是自行封装一个table 列拖拽组件。

效果演示：

具体效果如下：

难点概括

①element table header插槽应用

②drag知识点应用

③splice()方法理解

演示代码

<template>
  <div>
    <h1>基于element-ui table列拖拽实现</h1>
    <drag-head :head-columns="tableHead" :data="tableData"></drag-head>
  </div>
</template>
<script>
import DragHead from "./dragHead.vue";

export default {
  name: "DragHeadCase",

  components: { DragHead },

  data() {
    return {
      tableHead: [
        {
          label: "零零",
          prop: "v0",
          width: 150,
        },
        {
          label: "一一",
          prop: "v1",
          width: 150,
        },
        {
          label: "二二",
          prop: "v2",
          width: 150,
        },
        {
          label: "三三",
          prop: "v3",
          width: 150,
        },
        {
          label: "四四",
          prop: "v4",
          width: 300,
        },
        {
          label: "五五",
          prop: "v5",
        },
        {
          label: "六六",
          prop: "v6",
        },
        {
          label: "七七",
          prop: "v7",
        },
        {
          label: "八八",
          prop: "v8",
        },
        {
          label: "九九",
          prop: "v9",
        },
      ],

      tableData: [
        {
          v0: "2016-05-02",
          v1: "王小虎",
          v2: "上海",
          v3: "普陀区",
          v4: "上海市普陀区金沙江路 1518 弄",
          v5: 200333,
          v6: "2016-05-02",
          v7: "王小虎",
          v8: "上海",
          v9: "普陀区",
        },
        {
          v0: "2016-05-02",
          v1: "王小虎",
          v2: "上海",
          v3: "普陀区",
          v4: "上海市普陀区金沙江路 1518 弄",
          v5: 200333,
          v6: "2016-05-02",
          v7: "王小虎",
          v8: "上海",
          v9: "普陀区",
        },
        {
          v0: "2016-05-02",
          v1: "王小虎",
          v2: "上海",
          v3: "普陀区",
          v4: "上海市普陀区金沙江路 1518 弄",
          v5: 200333,
          v6: "2016-05-02",
          v7: "王小虎",
          v8: "上海",
          v9: "普陀区",
        },
        {
          v0: "2016-05-02",
          v1: "王小虎",
          v2: "上海",
          v3: "普陀区",
          v4: "上海市普陀区金沙江路 1518 弄",
          v5: 200333,
          v6: "2016-05-02",
          v7: "王小虎",
          v8: "上海",
          v9: "普陀区",
        },
        {
          v0: "2016-05-02",
          v1: "王小虎",
          v2: "上海",
          v3: "普陀区",
          v4: "上海市普陀区金沙江路 1518 弄",
          v5: 200333,
          v6: "2016-05-02",
          v7: "王小虎",
          v8: "上海",
          v9: "普陀区",
        },
      ],
    };
  },
};
</script>

table 列 拖拽组件实现代码

<template>
  <div style="width: 1000px">
    <el-table
      ref="elTable"
      border
      style="width: 100%"
      v-bind="$attrs"
      v-on="$listeners"
      :key="headKey"
      :cell-class-name="cellClassName"
      :header-cell-class-name="cellClassName"
    >
      <!-- 循环表头 -->
      <template v-for="(col, index) in tableHead">
        <el-table-column
          :key="index"
          :prop="col.prop"
          :align="col.align || 'center'"
          :width="col.width || 100"
        >
          <!-- 通过插槽为表头绑定mousedown和dragover方法 -->
          <template slot="header" slot-scope="{ column, $index }">
            <span
              @mousedown="handleMounseDown($event, column, $index)"
              @dragover="handleDragover($event, column, $index)"
            >
              {{ col.label }}
            </span>
          </template>
        </el-table-column>
      </template>
    </el-table>
  </div>
</template>

<script>
export default {
  props: {
    headColumns: Array,
  },

  mounted() {
    /** 备用操作（如果需要对headColumns数组操作） */
    this.tableHead = this.headColumns;
  },

  data() {
    return {
      tableHead: [],

      // 拖拽状态
      dragState: {
        start: -3, // 起始元素的 index 防止初始化cellStyle时序号、展开等默认样式改变，最好小于-3
        end: -3, // 移动鼠标时所覆盖的元素 index
        dragging: false, // 是否正在拖动
        direction: undefined, // 拖动方向
      },

      headKey: "dragHead", // 表头数组变换位置时，重绘table（不更新该值，表头数组变化时，页面不会改变）

      scrollX: 0, // 初始x轴scroll位置（用于定位X轴滚动条）
    };
  },

  methods: {
    /** 鼠标摁下触发 */
    handleMounseDown(e, column, $index) {
      this.dragState.dragging = true;
      this.dragState.start = parseInt($index - 0);
      // 添加鼠标抬起事件  消除鼠标摁下立刻松开问题
      document.addEventListener("mouseup", this.handleMouseUp);
      // 添加拖拽结束事件
      document.addEventListener("dragend", this.handleMouseUp);

      // 对选中的表头允许其拖拽
      const dragclass = ".el-table__header-wrapper ." + column.id;
      const dragDom = document.querySelectorAll(dragclass);
      dragDom.forEach((dom) => {
        // 允许表头块可以被拖拽 draggable 属性 不允许拖拽dragover等相关拖拽事件无法触发
        dom.setAttribute("draggable", true);
      });
    },

    /** 鼠标在拖拽移动时触发 */
    handleDragover(e, column, $index) {
      if (this.dragState.dragging) {
        // 获取当前滚动条的位置
        const scrollDom = this.$refs.elTable.bodyWrapper;
        this.scrollX = scrollDom.scrollLeft;
        const index = parseInt($index - 0); // 记录起始列
        /** 实时更改鼠标处于表头的位置 */
        if (index - this.dragState.start !== 0) {
          this.dragState.direction =
            index - this.dragState.start < 0 ? "left" : "right"; // 判断拖动方向
          this.dragState.end = parseInt($index - 0);
        } else {
          this.dragState.end = this.dragState.start;
          this.dragState.direction = null;
        }
      }
    },

    /** 鼠标抬起或拖拽结束触发 */
    handleMouseUp() {
      // 更新拖拽后的表头
      this.headDraged(this.dragState);
      const { end } = this.dragState;
      // 初始化拖动状态
      this.dragState = {
        start: end, //记录最后拖动的位置
        end: -9,
        dragging: false,
        direction: undefined,
      };
      document.removeEventListener("mouseup", this.handleMouseUp);
      document.removeEventListener("dragend", this.handleMouseUp);

      setTimeout(() => {
        // 重置拖拽状态
        this.dragState.start = -9;
      }, 500);
    },

    // 更新拖拽后的表头
    headDraged({ start, end, direction }) {
      if (direction) {
        const originColumn = this.tableHead[start];
        // 有位置交换时，原先位置的元素删除，再在目标处插入
        this.tableHead.splice(start, 1);
        this.tableHead.splice(end, 0, originColumn);
        this.headKey = new Date().getTime() + ""; // 更新table key值
        this.$nextTick(() => {
          // 因为表头重绘后滚动条会移到最左端初始位置，因此如果是在中间部分拖拽，还需要把滚动条在定位到该位置
          this.$refs.elTable.bodyWrapper.scrollLeft = this.scrollX;
        });
      }
    },

    // 拖动虚线样式设置
    cellClassName({ columnIndex }) {
      const { start, end, direction } = this.dragState;
      const target = columnIndex - 0;
      if (target === start) {
        // 被移动的元素
        return "drag_start";
      } else if (target === end) {
        // 要移动的位置
        return `drag_end_${direction}`;
      }
      return "";
    },
  },
};
</script>

<style lang="scss" scoped>
::v-deep .el-table {
  .drag_start {
    opacity: 0.8;
    background-color: rgba(0, 0, 0, 0.938);
    color: #f3e8e8fd;
    transition: all 0.3s cubic-bezier(0.23, 1, 0.32, 1);
  }
  .drag_end_left {
    border-left: 2px dotted rgba(0, 0, 0, 0.938);
  }
  .drag_end_right {
    border-right: 2px dotted rgba(0, 0, 0, 0.938);
  }
}
</style>

最后

该组件目前仅支持最简单的拖拽效果，后续开发出兼容fixed、checkbox、expand 以及操作列的组件会及时更新文章，有兴趣的朋友可以点赞收藏。