Get item from QGraphicScene

[Please_Help_me_D]

Hi,

In QGtaphicsScene I add few items. Then I use the flag QGraphicsItem::ItemSendsGeometryChanges and when the item is moved the program goes to the QVariant GraphicVertical::itemChange ( GraphicsItemChange change, const QVariant & value ) function.
Here I need to use either QGraphicsScene::items() or QGraphicsScene::itemAt()
When I use any of these:

QList<QGraphicsItem*> items = this->scene()->items(Qt::DescendingOrder);

or

QGraphicsItem *item = this->scene()->itemAt(20, 20, QTransform());

I get an exception error (in debug mode): (why?)
Application was stopped by the exception...

[Christian Ehrlicher]

Use a debugger and see where it crashes. I would guess scene() returns a nullptr.

[Please_Help_me_D]

@Christian-Ehrlicher yes! As you said this->scene() returnes zero
but why? How to overcome it?

---

EDIT

---

I understood now.
The scene() appears after some operations and as I write my code in itemChange I simply need to write:

    if (this->scene()){ // if the scene() exist then do the following
        QGraphicsItem *item = this->scene()->itemAt(mapToScene(20, 20), QTransform());
        QList<QGraphicsItem*> items = this->scene()->items(Qt::DescendingOrder);
    }

So thank you! you solved my problem!