我的程序要完成这样的功能：点击一条线，然后这条线条从黑色变为红色，同时弹出对话框，当这个对话框关闭时，线条颜色也同时从红色变为黑色。我的实现方法是，对话框继承QWidget类，重写closeEent虚函数，完成当对话框关闭时抛出自定义的信号coseS（），因为我要在实现线条颜色也同时从红色变为黑色，所以我就在继承QGraphicsLineItem的线条类中定义了SLOT，此时问题出现了，编译错误如下：
/home/jfzhang/plotnode/moc/moc_line.cpp:44: error: ‘staticMetaObject’ is not a member of ‘QGraphicsLineItem’
/home/jfzhang/plotnode/../qtsdk-2010.02/qt/include/QtCore/qobject.h:296: error: ‘QScopedPointer<QObjectData, QScopedPointerDeleter<QObjectData> > QObject::d_ptr’ is protected
/home/jfzhang/plotnode/moc/moc_line.cpp:54: error: within this context
/home/jfzhang/plotnode/../qtsdk-2010.02/qt/include/QtCore/qobject.h:296: error: object missing in reference to ‘QObject::d_ptr’
/home/jfzhang/plotnode/moc/moc_line.cpp:54: error: from this location
/home/jfzhang/plotnode/../qtsdk-2010.02/qt/include/QtCore/qobject.h:296: error: ‘QScopedPointer<QObjectData, QScopedPointerDeleter<QObjectData> > QObject::d_ptr’ is protected
/home/jfzhang/plotnode/moc/moc_line.cpp:54: error: within this context
/home/jfzhang/plotnode/../qtsdk-2010.02/qt/include/QtCore/qobject.h:296: error: object missing in reference to ‘QObject::d_ptr’
/home/jfzhang/plotnode/moc/moc_line.cpp:62: error: ‘qt_metacast’ is not a member of ‘QGraphicsLineItem’
/home/jfzhang/plotnode/moc/moc_line.cpp:67: error: ‘qt_metacall’ is not a member of ‘QGraphicsLineItem’
难道QGraphicsLineItem不能写SLOT或是SIGNAL
