QT运行出错：QObject::connect: Parentheses expected以及QObject::connect: No such slot ***

作者：2023面试高手 | 2024-03-23 20:02:48

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qobject::connect: parentheses expected, signal qcombobox::currentindexchange

我在QGraphicsScene子类中添加了item的弹出菜单，并连接Action到槽函数，结果槽函数不起作用，输出：QObject::connect: No such slot ***

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//选中item后弹出右键菜单
if (event->button() == Qt::RightButton)
{
    m_pItemSelected = nullptr;
    foreach (QGraphicsItem *item, items(event->scenePos()))
    {
         if (item->type() == QGraphicsPixmapItem::Type)
        {
            m_pItemSelected = item;
            QMenu menu;
            QAction *removeAction = menu.addAction( "Remove" );
            QAction *toTopLayerAction = menu.addAction( "To Top Layer" );
            QAction *toBottomLayerAction = menu.addAction( "To Bottom Layer" );
            QAction *toUpperLayerAction = menu.addAction( "To Upper Layer" );
            QAction *toLowerLayerAction = menu.addAction( "To Lower Layer" );
            connect(removeAction, SIGNAL(triggered()), this , SLOT(slotRemoveItem()));
            connect(toTopLayerAction, SIGNAL(triggered()), this , SLOT(slotLayerTop()));
            connect(toBottomLayerAction, SIGNAL(triggered()), this , SLOT(slotLayerBottom()));
            connect(toUpperLayerAction, SIGNAL(triggered()), this , SLOT(slotLayerUpper()));
            connect(toLowerLayerAction, SIGNAL(triggered()), this , SLOT(slotLayerLower()));
            menu.exec(event->screenPos());
             break ;
        }
    }
}

在类中使用信号/槽时一定要加Q_OBJECT宏，signal和slots的参数要一样

槽函数加()： connect(toTopLayerAction, SIGNAL(triggered()), this, SLOT(slotLayerTop())); // 正确

切记忘了()：connect(toTopLayerAction, SIGNAL(triggered()), this, SLOT(slotLayerTop)); // 错误

转载于:https://www.cnblogs.com/MakeView660/p/10369462.html

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