Using QPropertyAnimation with QGraphicsPixmapItem

Hi! Is it possible to use QPropertyAnimation with a QGraphicsPixmapItem? I read it is possible by creating a subclass and making it inherit from QObject as well. So, I created it and defined the property like:

Code:

---

class MyPixmap : public QObject, public QGraphicsPixmapItem {
   Q_OBJECT
   Q_PROPERTY (qreal rotation READ rotation WRITE setRotation)
...

---

but when running the animation I get a crash. I made the same for a QGraphicsItem and it worked, but this isn't. Any idea why?
Thanks!

that is strange. Run a debugger and see where exactly your app crashes.

I already tried that: it crashes when it executes the instruction:

Code:

---

QPropertyAnimation* anim = new QPropertyAnimation(item, "rotation");

---

I checked item and it seems it's my class correctly, not a NULL pointer. Everything seems OK to me... any idea? Thanks!

what does the backtrace say?

Well, it must be in your definition of the class. Following works fine on my system:

Code:

---

class MyPixmap : public QObject, public QGraphicsPixmapItem
{
  Q_OBJECT
  Q_PROPERTY (qreal rotation READ rotation WRITE setRotation)
};
 
int main(int argc, char **argv)
{
  QApplication app(argc, argv);
  MyPixmap *it = new MyPixmap();
  QPropertyAnimation* anim = new QPropertyAnimation(it, "rotation");
  qWarning() << anim->propertyName();
  delete anim;
  delete it;
  return 0;
}

---

I get: undefined reference to `vtable for MyPixmap'...

Well here is the full code. You have to rerun qmake:

Code:

---

#include <QtGui>
 
class MyPixmap : public QObject, public QGraphicsPixmapItem
{
  Q_OBJECT
  Q_PROPERTY (qreal rotation READ rotation WRITE setRotation)
};
 
int main(int argc, char **argv)
{
  QApplication app(argc, argv);
  MyPixmap *it = new MyPixmap();
  QPropertyAnimation* anim = new QPropertyAnimation(it, "rotation");
  qWarning() << anim->propertyName();
  delete anim;
  delete it;
  return 0;
}
 
#include "main.moc"

---

Yes, now its working... There must be an error in my implementation. I will try to find it. Anyway, another solution was to use a QGraphicsProxyWidget. From the point of view of the performance (of animations for instance), is there any difference between using QGraphicsPixmapItems or other types of items like QGraphicsProxyWidgets? Sometimes I wonder if it would be better to use widgets or items in QGraphicsView to play animations.
Thanks for the information!

I would go for a normal item since it is not so big and heavy like a QGraphicsWidget. But if you only use a small number it does not make a big difference.