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
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