How to make the QGraphicsScene to redraw it's foreground?

I've tried:
QGraphicsView::invalidateScene()
QGraphicsView::updateSceneRect()
QGraphicsScene::invalidate()
QGraphicsScene::update()

but it only calls QGraphicsView::drawForeground(), and never the QGraphicsScene::drawForeground(). Can someone tell me where can be the problem? Thanks ...

Tomas