QGraphicsItemGroup 类

QGraphicsItemGroup 类提供将一组项视为单项的容器。更多...

头：	#include <QGraphicsItemGroup>
qmake:	QT += widgets
Since:	Qt 4.2
继承：	QGraphicsItem

该类在 Qt 4.2 引入。

所有成员列表，包括继承成员

公共类型

enum	anonymous { Type }

公共函数

	QGraphicsItemGroup (QGraphicsItem * parent = nullptr)
virtual	~QGraphicsItemGroup ()
void	addToGroup (QGraphicsItem * item )
void	removeFromGroup (QGraphicsItem * item )

重实现公共函数

virtual QRectF	boundingRect () const override
virtual bool	isObscuredBy (const QGraphicsItem * item ) const override
virtual QPainterPath	opaqueArea () const override
virtual void	paint (QPainter * painter , const QStyleOptionGraphicsItem * option , QWidget * widget = nullptr) override
virtual int	type () const override

详细描述

A QGraphicsItemGroup is a special type of compound item that treats itself and all its children as one item (i.e., all events and geometries for all children are merged together). It's common to use item groups in presentation tools, when the user wants to group several smaller items into one big item in order to simplify moving and copying of items.

If all you want is to store items inside other items, you can use any QGraphicsItem directly by passing a suitable parent to setParentItem ().

The boundingRect () function of QGraphicsItemGroup returns the bounding rectangle of all items in the item group. QGraphicsItemGroup ignores the ItemIgnoresTransformations flag on its children (i.e., with respect to the geometry of the group item, the children are treated as if they were transformable).

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 (). To dismantle ("ungroup") an item group, you can either call QGraphicsScene::destroyItemGroup (), or you can manually remove all items from the group by calling removeFromGroup ().

// Group all selected items together
QGraphicsItemGroup *group = scene->createItemGroup(scene->selecteditems());
// Destroy the group, and delete the group item
scene->destroyItemGroup(group);

The operation of adding and removing items preserves the items' scene-relative position and transformation, as opposed to calling setParentItem (), where only the child item's parent-relative position and transformation are kept.

The addtoGroup() function reparents the target item to this item group, keeping the item's position and transformation intact relative to the scene. Visually, this means that items added via addToGroup () will remain completely unchanged as a result of this operation, regardless of the item or the group's current position or transformation; although the item's position and matrix are likely to change.

The removeFromGroup () function has similar semantics to setParentItem (); it reparents the item to the parent item of the item group. As with addToGroup (), the item's scene-relative position and transformation remain intact.

另请参阅 QGraphicsItem and 图形视图框架 .

成员类型文档编制

enum QGraphicsItemGroup:: anonymous

值的返回通过虚拟 type () 函数。

常量	值	描述
`QGraphicsItemGroup::Type`	`10`	图形项组

成员函数文档编制

QGraphicsItemGroup:: QGraphicsItemGroup ( QGraphicsItem * parent = nullptr)

构造 QGraphicsItemGroup。 parent 会被传递给 QGraphicsItem 的构造函数。

另请参阅 QGraphicsScene::addItem ().

`[虚拟]` QGraphicsItemGroup:: ~QGraphicsItemGroup ()

销毁 QGraphicsItemGroup .

void QGraphicsItemGroup:: addToGroup ( QGraphicsItem * item )

添加给定 item and item's child items to this item group. The item and child items will be reparented to this group, but its position and transformation relative to the scene will stay intact.

另请参阅 removeFromGroup () 和 QGraphicsScene::createItemGroup ().

`[override virtual]` QRectF QGraphicsItemGroup:: boundingRect () const

重实现： QGraphicsItem::boundingRect () const.

Returns the bounding rect of this group item, and all its children.

`[override virtual]` bool QGraphicsItemGroup:: isObscuredBy (const QGraphicsItem * item ) const

重实现： QGraphicsItem::isObscuredBy (const QGraphicsItem *item) const.

`[override virtual]` QPainterPath QGraphicsItemGroup:: opaqueArea () const

重实现： QGraphicsItem::opaqueArea () const.

`[override virtual]` void QGraphicsItemGroup:: paint ( QPainter * painter , const QStyleOptionGraphicsItem * option , QWidget * widget = nullptr)

重实现： QGraphicsItem::paint (QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget).

void QGraphicsItemGroup:: removeFromGroup ( QGraphicsItem * item )

移除指定 item from this group. The item will be reparented to this group's parent item, or to 0 if this group has no parent. Its position and transformation relative to the scene will stay intact.

另请参阅 addToGroup () 和 QGraphicsScene::destroyItemGroup ().

`[override virtual]` int QGraphicsItemGroup:: type () const

重实现： QGraphicsItem::type () const.