[SOLVED]remove a QGraphicsItem from a QGraphicsScene.

[issam]

hi all,

I have a problem when i try to remove a graphicsItem from a QGraphicsScene instance. The message error is :

QGraphicsScene::removeItem: item 0x844c398's scene (0x0) is different from this scene (0x8386188)

Have someone an idea ?

[mcosta]

HI,

can you post your code?
The error means that you never added the item to the scene.

[issam]

This is a small portion of the code :

The item class :
@
class Place : public QObject, public QGraphicsEllipseItem
{
Q_OBJECT
public:
enum { Type = UserType + 1 };

Place (int number);
~Place ();
}
@

Add the item :

@
switch(scenemode)
{
case 0 :
Place * place;
place = new Place(places_indexs);
this->addItem(place);
place->setPos(mouseEvent->scenePos().x() - place->boundingRect().width() / 2,
mouseEvent->scenePos().y());
emit itemInserted(0);
places_indexs++;

 break;
case 1:
 break;
/* ............ */

}
@

I use a QMainWindows as the application's main window. The cental area is a TabView and each tab contains a QGraphicsSene !

[mcosta]

Hi,

in the second piece of code, this is a pointer to GraphicsScene?

[issam]

yes, this is a pointer to GraphicsScene !

[ChrisW67]

You are:

• adding the item to a scene other than the one you think you are;
• trying to remove it from scene other than the one it was inserted in; or
• trying to remove an item that was deleted earlier (which removes it from the owning scene and means you are using a dangling pointer).

It would help if we had some code that related to the removeItem call that fails, and some context for where/when this happens.

[issam]

Hi, friend ! I have posted, before the site crash, the code. I have solved the problem.
The problem is that : in the scene i added three items : pathitem, ellipse and rectangle. Each item had a grahicstextitem children as label. the label is movable and selectable. So, when i selected the three items, the labels are also selected as separated items. thus, the selectedItems() method will return 6 selected items in a list not 3 as i thought. And so when i delete a parent item its children in the list remains without parent, so without scene ;) this is the problem.
the correct code is :

@
/* remove selected item(s) */
void PNetScene::removeItems()
{
if(selectedItems().isEmpty())
return;

foreach(QGraphicsItem * item, selectedItems())
if(item->type() == QGraphicsSimpleTextItem::Type
|| item->type() == Rectangle::Type)
item->setSelected(false);

foreach(QGraphicsItem * item, selectedItems()){
if(item->type() == Arrow::Type)
{
Arrow * arrow = qgraphicsitem_cast<Arrow*>(item);
removeItem(item);
QGraphicsItem * sourceItem = arrow->getStartItem();
QGraphicsItem * destItem = arrow->getEndItem();

if(sourceItem->type() == Place::Type)
qgraphicsitem_cast<Place*>(sourceItem)->deleteRelation(arrow);
else if(sourceItem->type() == Transition::Type)
qgraphicsitem_cast<Transition*>(sourceItem)->deleteRelation(arrow);
if(destItem->type() == Place::Type)
qgraphicsitem_cast<Place*>(destItem)->deleteRelation(arrow);
else if(destItem->type() == Transition::Type)
qgraphicsitem_cast<Transition*>(destItem)->deleteRelation(arrow);

delete item;
}
}

foreach(QGraphicsItem * item, selectedItems())
{
removeItem(item);
delete item;
}

}
@

Thanks for the help. :)