效果：

1.

<a-table
            :expandIcon="expandIcon"
            :loading="loading"
            :columns="columns"
            :data-source="data"
            class="components-table-demo-nested"
            @change="onChangeTable"
            :scroll="{x:1300,y:y}"
            :pagination="pagination"
            :locale="locale"
          >

2.在方法methods下加入方法

expandIcon(props) {
      // console.log(props);
        if (props.record.fileInfoList.length > 0) {
          if (props.expanded) {//有数据-展开时候图标
            return (
              <a
                style="color: 'black',margin-right:0px"
                onClick={(e) => {
                  props.onExpand(props.record, e);
                }}
              >
                <a-icon type="down" />{" "}
              </a>
            );
          } else {//有数据-未展开时候图标
            return (
              <a
                style="color: 'black' ,margin-right:0px"
                onClick={(e) => {
                  props.onExpand(props.record, e);
                }}
              >
                <a-icon type="right" />
              </a>
            );
          }
        } else {//无数据-图标
          return (
            <span style="margin-right:0px">
              <a-icon type="smile" />
            </span>
          );
        }
    },