QGraphicsView::mousePressEvent(event);

to the end of mousePressEvent-function in my QGraphicsView.
Unfortunately it doesn't work. I receive no mousePressEvent in my Node class.
My mousePressEvent in the QGraphicsView derived class:

void GraphWidget::mousePressEvent(QMouseEvent *event){

    if (event->button() == Qt::RightButton) // doesn't matter I think
    {
        rightMousePressed = true;
        _panStartX = event->x();
        _panStartY = event->y();
        setCursor(Qt::ClosedHandCursor);
        event->accept();
        return;
    }
    QGraphicsView::mousePressEvent(event);
}

I also tried to get the selected Node this way (in the QGraphicsView class also in the MousePressEvent-func):

    Node *myNode = static_cast<Node*>(itemAt(event->pos()));
    qDebug() << "selected node: " << myNode;
    myNode->speak(); // speak() is a funtion in my Node class
    setSelectedNode(myNode);

and this way (also in the QGraphicsView class also in the MousePressEvent-func) :

    for(Node* i : all_nodes){
        if(i->isSelected()){
            setSelectedNode(i); // selectedNode is a Node* attribute of my QGraphicsView class
            i->speak();
            break;
        }
    }

Both ways don't work. The program just crashes when I click to the scene.
This is the constructor of my QGraphicsItem derived class:

Node::Node(GraphWidget *graphWidgetInput)
{
    setFlag(ItemIsMovable);
    setFlag( ItemIsSelectable, true );
    setFlag(ItemSendsGeometryChanges);
    setCacheMode(DeviceCoordinateCache);
    setZValue(-1);
    graph = graphWidgetInput;
    width = 100;
    height = 100;
}

Any ideas what I missed?
Thanks for answers