iview tree组件如何能选中文字的时候展开当前列 on-select-change 无效

Question

    <Tree class="tree-content" :data="treeData" :load-data="loadData" ref="tree" @on-select-change="selectChange" :render="renderContent"></Tree>

    selectChange(selectedList) {
      const node = selectedList[selectedList.length - 1];
      console.log(selectedList);
      if (node) {
        this._loadData(node.id, response => {
          if (!response) return;
          let array = [];
          response.forEach(item => {
            array.push(item);
            this._loadData(item.id, () => {});
          });
          node.children = array;
          node.expend = true; // 展开子节点
        });
      }
    },

selectChange 完全无效，点击文字无法展开，求原因