I have a QGraphicsViewScene that displays a few QGraphicsPolygonItems. I created a class called DiagramItem that is based on QgraphicsPolygonItems. I wanted each polygon item to toggle it's "state" every 10 seconds after it was created. So I added a "state" member to my DiagramItem class called "zoneState."

I saw that for a QTimer to work, it had to be a QObject. So I added QObject as one of the base classes and added the macro Q_OBJECT to the header class. Now it fails to compile. It gives me the error: "undefined reference to 'vtable for DiagramItem.' What is going on? It seems like it should be something pretty basic. Please advise!




Here is my header file "diagramitem.h"

Qt Code: 
  1. #include <QTimer>
  2. #include <QObject>
  3. #include <QGraphicsObject>
  4.  
  5. #include "scribblearea.h"
  6.  
  7. QT_BEGIN_NAMESPACE
  8. class QPixmap;
  11. class QTextEdit;
  13. class QMenu;
  15. class QPainter;
  17. class QWidget;
  18. class QPolygonF;
  19. QT_END_NAMESPACE
  20.  
  21. //! [0]
  22. class DiagramItem : public QObject, public QGraphicsPolygonItem
  23. {
  24.     Q_OBJECT
  25. public:
  26. QTimer* iTimer;
  27. QTime*  timeValue;
  28.  bool zoneState;
  29.  
  30. public:
  31.     enum { Type = UserType + 15 };
  32.  
  33.     DiagramItem(ScribbleArea *scribble, QGraphicsScene *scene = 0,QGraphicsItem *parent = 0);
  34.     QPolygonF polygon() const
  35.         { return myPolygon; }
  36.  
  37.     int type() const
  38.         { return Type;}
  39.     void toggleState();
  40.     bool getState();
  41.  
  42.     /*
  43. public Q_SLOTS:
  44.     void start(int msec);
  45.     void start();
  46.     void stop();
  47.  
  48. public slots:
  49. */
  50.  
  51. private:
  52.     QPolygonF myPolygon;
  53.  
  54.  
  55. };
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Here is "diagramitem.cpp"
Qt Code: 
  1. #include <QtGui>
  2. #include <QObject>
  3.  
  4. #include "diagramitem.h"
  5.  
  6.  
  7. //! [0]
  8. DiagramItem::DiagramItem(ScribbleArea *scribble, QGraphicsScene *scene,QGraphicsItem *parent)
  9.     : QGraphicsPolygonItem(parent, scene)
  10. {
  11.     zoneState = false;
  12.   //  iTimer = new QTimer();
  13.  
  14.   /*  QTimer *timer = new QTimer();
  15.          connect(timer, SIGNAL(timeout()), this, SLOT(toggleState()));
  16.          timer->start(1000);
  17. */
  18.  
  19.     //QObject::connect(iTimer,SIGNAL(timeout()),scribble,SLOT(timerToggle()));
  20.  
  21.     QPolygon p = scribble->getPoly();
  22.  
  23.      myPolygon << p.point(0) << p.point(1)<< p.point(2) << p.point(3);
  24.  
  25.  
  26.     setPolygon(myPolygon);
  27.     setFlag(QGraphicsItem::ItemIsMovable, true);
  28.     setFlag(QGraphicsItem::ItemIsSelectable, true);
  29.     setFlag(QGraphicsItem::ItemSendsGeometryChanges, true);
  30. }
  31.  
  32. //! [5]
  33. void DiagramItem::toggleState()
  34. {
  35.     if(zoneState)
  36.         zoneState = false;
  37.     else
  38.         zoneState = true;
  39. }
  40.  
  41. bool DiagramItem::getState()
  42. {
  43.     return zoneState;
  44.  
  45. }
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