oh, yes, i misspelt double, thank you.
now the following:
at first double click, I still receive mosuePressEvent, after that I correctly receive mouseDoubleClickEvent.
and then I always receive the same mouseDoubleClickEvent, it doesn't matter where I double click on my QGraphicsView!!!

but I still don't receive mousePressEvent und mouseMoveEvent. I have to go mad!!!

setMouseTracking(true) doen't help. I want to receive a mouseEvent only on click, double click, and move (press mouse button, move, release mouse button) and not mouse over etc.

I hope somebody can help me