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

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 ***

 C++ Code 
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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

posted on 2019-02-13 13:55  我来乔23  阅读(10407)  评论(0编辑  收藏  举报

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