Question

这是我的第一个职位。我最近开始使用QT和C++。令人印象深刻。我似乎无法处理一个问题。基本上,Im试图将许多<代码>QGraphicsItems组织成两个<代码>QGraphicsItemgroups。这些项目使用<条码>QGraphicsScene在<条码>上显示。制造这些物品和展示这些物品都是一种药店。然而,当我加入这一组别时,该方案每次都坠毁了指挥部。之所以增加这些组别,是因为后来能够选择哪些项目在油漆中生产。相关守则列于下文。

QGraphicsScene * scene;
scene = new QGraphicsScene(this);
ui.graphicsView->setScene(scene);

QBrush whiteBrush;
QBrush imageBrush;
QPen blackPen;
whiteBrush = QBrush(Qt::white);
imageBrush = QBrush(Qt::lightGray);
blackPen = QPen(Qt::black);
blackPen.setWidth(1);

QGraphicsItemGroup * cliGroup;
QGraphicsItemGroup * alfGroup;
cliGroup = new QGraphicsItemGroup;
alfGroup = new QGraphicsItemGroup;
scene->addItem(cliGroup);
scene->addItem(alfGroup);

QGraphicsPolygonItem *poly;
poly =  scene->addPolygon(polyF, blackPen, imageBrush);
cliGroup->addToGroup(poly);        //line it crashes on

我怀疑,这在现场制造多动,然后在<条码>QGraphicsItemGroup上添加,尽管我可以说明如何改变这种说法。我从那时起就采用了一种不太明智的解决办法,即根据类型对现场的物品进行过滤,但这只是短期和表面的。任何建议?

Answer 1

http://doc.qt.nokia.com/latest/qgraphicsitemgroup.html#addTogroup” rel=“nofollow”QGraphicsItemGroup 文件:

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().

因此,按照Pete的建议,我将尝试如下:

QList<QGraphicsItem*> groupItems;
groupItems.append(poly); // add more items if you want
// Finally  construct the group
QGraphicsItemGroup * cliGroup = scene->createItemGroup(groupItems);

Answer 2

Rather than using new QGraphicsItemGroup, use QGraphicsScene::createItemGroup.

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