【开发记录】vue3实现列表拖拽排序，如何阻止放下后，元素回落？

一、问题描述

写了一个列表的拖拽排序，但遇到一个问题，就是拖拽放下后，html元素总会有一个回落的默认效果，这个会影响排序效果。

二、解决

其实，最后解决的办法，也很简单，就是在dragover事件处理中，去除默认，也就是e.preventDefault();

 const onDragOver = (e: any, index: number) => {
    e.preventDefault();
    // ....
 }

三、最后，记录一下完整的代码实现

<template>
  <div>
    <div class="card-list">
      <div
        class="card-item"
        :class="{'drag-over': dragOverIndex === index, 'active': dragData.index == index}"
        v-for="(item, index) in dataList"
        :key="item.cocosData.id"
        :id="item.cocosData.id"
        draggable="true"
        @dragstart.stop="onDragStart($event, index)"
        @dragover.stop="onDragOver($event, index)"
        @dragend.stop="onDragend"
      >
        <span>{{ item }}</span>
      </div>
    </div>
  </div>
</template>

<script lang="ts">
import { ref } from "vue";

export default defineComponent({
    name: "DragSort",
    setup(props) {
        const dataList = ref<string[]>([
            "字母A",
            "字母B",
            "字母D",
            "p",
        ]);
        
        const dragData = ref<any>({});
        const onDragStart = (e: any, index: number) => {
          dragData.value = {
            index,
          }
        }
        const dragOverIndex = ref(-1);
        const onDragOver = (e: any, index: number) => {
          e.preventDefault();
          if (dragData.value.index != index) {
            dragOverIndex.value = index;
          } else {
            dragOverIndex.value = -1;
          }
        }
        const onDragend = (e: any) => {
          e.preventDefault();
          const dragIndex = dragData.value.index;
          console.log('onDragend', dragIndex, dragOverIndex.value);
          if (dragIndex != dragOverIndex.value && dragOverIndex.value != -1) {
            const dragItem = _.cloneDeep(cocosdata.value["children"][dragIndex]);
            console.log('dragItem', dragItem);
            if (dragOverIndex.value > dragIndex) {
              cocosdata.value["children"].splice(dragOverIndex.value + 1, 0, dragItem);
              cocosdata.value["children"].splice(dragIndex, 1);
            } else {
              cocosdata.value["children"].splice(dragIndex, 1);
              cocosdata.value["children"].splice(dragOverIndex.value, 0, dragItem);
            }
          }
          dragOverIndex.value = -1;
          dragData.value = {};
        }
        
        return {
          dataList,
          onDragStart,
          onDragOver,
          dragOverIndex,
          onDragend,
          dragData,
        };
    },
});

</script>

<style lang="less" scoped>
.card-list {
  margin-top: 10px;
  .card-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    border: 1px solid transparent;
    position: relative;
    &.active {
      background-color: #f2f2f2;
    }
    &.drag-over {
      background-color: #ddd;
      border: 1px solid #aaa;
    }
    span {
      cursor: pointer;
    }
  }
}
</style>

四、最后

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