Adding an Item to QGraphicsItemGroup Makes It Invisible

The code below

QGraphicsEllipseItem *ellipse = addEllipse(x, y, 6, 6, series_pen);
ellipse->translate(-ellipse->boundingRect().width() / 2,
                   -ellipse->boundingRect().height() / 2);
ellipse->setToolTip(label);

draws the QGraphicsEllipseItem on a QGraphicsScene. However, the following code doesn't:

QGraphicsEllipseItem *ellipse = addEllipse(x, y, 6, 6, series_pen);
ellipse->translate(-ellipse->boundingRect().width() / 2,
                   -ellipse->boundingRect().height() / 2);
ellipse->开发者_开发百科setToolTip(label);

QGraphicsItemGroup *g = new QGraphicsItemGroup;
g->addToGroup(ellipse);

What is wrong if I add a QGraphicsItem in QGraphicsItemGroup?

I'm using Qt Creator 2.2.1, Qt 4.7.4 (32 bit) on Windows 7.

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From the Qt manual page for QGraphicsItemGroup:

There are two ways to construct an item group. The easiest and most common approach is to pass a list of items (e.g., all selected items) to QGraphicsScene::createItemGroup(), which returns a new QGraphicsItemGroup item. The other approach is to manually construct a QGraphicsItemGroup item, add it to the scene calling QGraphicsScene::addItem(), and then add items to the group manually, one at a time by calling addToGroup().

Sounds like your code needs to call QGraphicsScene::addItem().

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QGraphicsItemGroup is also a QGraphicsItem, so you need to add it to the scene, for its children to be drawn too.