QGraphicsObject rewrite boundingRect() and shape()

hi,my problem is that I have a class inherited from QGraphicsObject,and I have a private QPixmap variable car.All I want to do is draw this car image in the scene.I want to draw many cars like this.And I need to know whether two cars collides with each other.I rewrite two functions boundingRect() and shape(),but it do not work.Here is my code:
QRectF Car::boundingRect() const
{
return QRectF(QPointF(0,0),car.size());

}QPainterPath Car::shape() const
{
QPainterPath path;
path.addRect(boundingRect());
return path;
}
Does anything go wrong?

Thus far it is ok. What about the rest of the code? :)

Car item1;
item1.setPos(95,66);
Car item2;
item2.setPos(300,66);
scene.addItem(&item1);
scene.addItem(&item2);
if(item1.collidesWithItem(&item1))
qDebug()<<"items collides with item2";

Hera is my test code.actually two two cars don't collides with each other,but it prints "items collides with item2".I think it is my shape() problem.

You should use [code]...[/code] tags around code.

Code:

---

Car item1;
item1.setPos(95,66);
Car item2;
item2.setPos(300,66);
scene.addItem(&item1);
scene.addItem(&item2);
if(item1.collidesWithItem(&item1))
    qDebug()<<"items collides with item2";

---

Line 7 asks if item1 collides with itself. It does, so you print the misleading message.