解决elementui中el-table表格首次expand展开不能正常渲染展开页面里面的表格内容

<el-table 
:data="tableData"
ref="table" 
@row-click="rowClick"
@expand-change="expandChange">
<!-- 展开内容---------------------------------------- -->
<el-table-column type="expand">
    <template slot-scope="scope">
        <el-table 
        :key="updateChildTable" //这句是关键代码，修改key对应的变量值，刷新表格渲染
        :data="scope.row.children"  
        >
            <el-table-column prop="字段键值" label="列名" width="300">
                <template slot-scope="scope">
                    {{ scope.row.字段键值 }}
                </template>
            </el-table-column>
        </el-table>
    </template>
</el-table-column>
<!-- ---------------------------------------- -->
</el-table>
data(){
    return{
        updateChildTable:false,//刷新表格专用
    }
},
// 展开
rowClick(row, column, event) {
    row.isExpand = !row.isExpand;
    this.$refs.table.toggleRowExpansion(row, row.isExpand);
},
// 监听展开变化
expandChange(row, expanded) {
    let isExpand = expanded.find(v => v.ID == row.ID);//如果有匹配项代表已经展开
    row.isExpand = isExpand;
    if (isExpand) {
        this.$d.接口({ ID: row.ID, }, {
            s: (d) => {
                row.children = d;
                this.updateChildTable = !this.updateChildTable;//实时修改这个值刷新子表格渲染数据
            }
        });
    }
},