QTreeWidgetItem *root;    
root = new QTreeWidgetItem(ui->treeWidget, QStringList(QString("Connection")));
QVariant var0(0);
root->setData(0,Qt::UserRole,var0);

void MainWindow::on_treeWidget_customContextMenuRequested(QPoint pos)
{
    QTreeWidgetItem* curItem=ui->treeWidget->itemAt(pos); //获取当前被点击的节点 if(curItem==NULL)return; //这种情况是右键的位置不在treeItem的范围内，即在空白位置右击 QVariant var = curItem->data(0,Qt::UserRole); if(0 == var) //data(...)返回的data已经在之前建立节点时用setdata()设置好   {
       QMenu *popMenu =new QMenu(this);//定义一个右键弹出菜单  popMenu->addAction(ui->action_newDB);//往菜单内添加QAction   该action在前面用设计器定义了 popMenu->addAction(ui->action_openDB);
       popMenu->addAction(ui->action_delDB);
       popMenu->exec(QCursor::pos());//弹出右键菜单，菜单位置为光标位置  } else {
        QMenu *popMenu =new QMenu(this);//定义一个右键弹出菜单  popMenu->addAction(ui->action_newTable);//往菜单内添加QAction   该action在前面用设计器定义了 popMenu->addAction(ui->action_openTable);
        popMenu->addAction(ui->action_designTable);
        popMenu->exec(QCursor::pos());//弹出右键菜单，菜单位置为光标位置  }
}