QLayout *layout = this->ui->frameWindow->layout();
    if (layout != nullptr){
        for (int i = layout->count()-1; i >= 0; i--)    //倒序删除，reverse deleting to avoid Count changed in the middle of process
        {
            QLayoutItem* layoutItem = layout-> itemAt(i);
            layout->removeItem(layoutItem);
            if (layoutItem->widget() != nullptr)        //QLayoutItem可能包含widget（如QWidgetItem），也可能不包含widget（如QLayout、QSpacerItem）
                layoutItem->widget()->deleteLater();    //不删除会残留痕迹
        }
        delete layout;
    }