Qt add extended QGraphicsItem to scene

Question

I have created a class Atom that extends the Qt class QGraphicsItem like this:

Atom::Atom(qreal rad, qreal mass, int element, int state) : QGraphicsItem()
{
    // Initialization code
}
void Atom::changeState(int newState)
{
    // Code...
}

Then, I add my atom to the scene like this:

Atom *a=new Atom(rad,mass,element,state);
a->setPos(pos);
scene->addItem(a);

However, Qt converts my Atom class to a QGraphicsItem class. Now, when I call scene->items(), I get a QList of QGraphicsItems, which do not have the properties and methods of my Atom class.

So, I am asking the question: How would I go about getting a list of the Atoms that I have added to my QGraphicsScene?

Thanks.

score 2 · Answer 1 · edited May 23 '17 at 12:11

2

You'll need to cast the QGraphicsItems to Atoms. Please see this question for details:

Subclassing QGraphicsItem prevents me from being able to use itemAt() on a QGraphicsScene/View

edited May 23 '17 at 12:11

Community

1
1

answered Feb 05 '12 at 20:19

Anthony

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score 1 · Accepted Answer · answered Feb 05 '12 at 20:22

1

No. Your items are not converted to anything. They are still of your custom type. In C++, all objects of a derived class are also of class they derive from. Nothing is converted so nothing is lost.

Do a dynamic_cast<Atom*>(item) and you will get your item back.

answered Feb 05 '12 at 20:22

Stephen Chu

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Thanks. What is the difference between: `dynamic_cast(item)` vs `((Atom*)item)`? – Joel Feb 05 '12 at 20:30
@Joel: http://stackoverflow.com/questions/28002/regular-cast-vs-static-cast-vs-dynamic-cast – Mat Feb 05 '12 at 20:36
Thanks. I think I understand now. – Joel Feb 05 '12 at 20:42

Qt add extended QGraphicsItem to scene

2 Answers2