QGraphicsItemAnimation Class

The QGraphicsItemAnimation class provides simple animation support for QGraphicsItem. More...

Header:	#include <QGraphicsItemAnimation>
qmake:	QT += widgets
Since:	Qt 4.2
Inherits:	QObject

This class is obsolete. It is provided to keep old source code working. We strongly advise against using it in new code.

This class was introduced in Qt 4.2.

Public Functions

	QGraphicsItemAnimation(QObject *parent = nullptr)
virtual	~QGraphicsItemAnimation()
void	clear()
qreal	horizontalScaleAt(qreal step) const
qreal	horizontalShearAt(qreal step) const
QGraphicsItem *	item() const
QPointF	posAt(qreal step) const
QList<QPair<qreal, QPointF>>	posList() const
qreal	rotationAt(qreal step) const
QList<QPair<qreal, qreal>>	rotationList() const
QList<QPair<qreal, QPointF>>	scaleList() const
void	setItem(QGraphicsItem *item)
void	setPosAt(qreal step, const QPointF &point)
void	setRotationAt(qreal step, qreal angle)
void	setScaleAt(qreal step, qreal sx, qreal sy)
void	setShearAt(qreal step, qreal sh, qreal sv)
void	setTimeLine(QTimeLine *timeLine)
void	setTranslationAt(qreal step, qreal dx, qreal dy)
QList<QPair<qreal, QPointF>>	shearList() const
QTimeLine *	timeLine() const
QTransform	transformAt(qreal step) const
QList<QPair<qreal, QPointF>>	translationList() const
qreal	verticalScaleAt(qreal step) const
qreal	verticalShearAt(qreal step) const
qreal	xTranslationAt(qreal step) const
qreal	yTranslationAt(qreal step) const

Public Slots

void	setStep(qreal step)

Protected Functions

virtual void	afterAnimationStep(qreal step)
virtual void	beforeAnimationStep(qreal step)

Detailed Description

The QGraphicsItemAnimation class animates a QGraphicsItem. You can schedule changes to the item's transformation matrix at specified steps. The QGraphicsItemAnimation class has a current step value. When this value changes the transformations scheduled at that step are performed. The current step of the animation is set with the setStep() function.

QGraphicsItemAnimation will do a simple linear interpolation between the nearest adjacent scheduled changes to calculate the matrix. For instance, if you set the position of an item at values 0.0 and 1.0, the animation will show the item moving in a straight line between these positions. The same is true for scaling and rotation.

It is usual to use the class with a QTimeLine. The timeline's valueChanged() signal is then connected to the setStep() slot. For example, you can set up an item for rotation by calling setRotationAt() for different step values. The animations timeline is set with the setTimeLine() function.

An example animation with a timeline follows:

     QGraphicsItem *ball = new QGraphicsEllipseItem(0, 0, 20, 20);

     QTimeLine *timer = new QTimeLine(5000);
     timer->setFrameRange(0, 100);

     QGraphicsItemAnimation *animation = new QGraphicsItemAnimation;
     animation->setItem(ball);
     animation->setTimeLine(timer);

     for (int i = 0; i < 200; ++i)
         animation->setPosAt(i / 200.0, QPointF(i, i));

     QGraphicsScene *scene = new QGraphicsScene;
     scene->setSceneRect(0, 0, 250, 250);
     scene->addItem(ball);

     QGraphicsView *view = new QGraphicsView(scene);
     view->show();

     timer->start();

Note that steps lie between 0.0 and 1.0. It may be necessary to use setUpdateInterval(). The default update interval is 40 ms. A scheduled transformation cannot be removed when set, so scheduling several transformations of the same kind (e.g., rotations) at the same step is not recommended.

See also QTimeLine and Graphics View Framework.

Member Function Documentation

QGraphicsItemAnimation::QGraphicsItemAnimation(QObject **parent* = nullptr)

Constructs an animation object with the given parent.

`[slot]` void QGraphicsItemAnimation::setStep(qreal step)

Sets the current step value for the animation, causing the transformations scheduled at this step to be performed.

`[virtual]` QGraphicsItemAnimation::~QGraphicsItemAnimation()

Destroys the animation object.

`[virtual protected]` void QGraphicsItemAnimation::afterAnimationStep(qreal step)

This method is meant to be overridden in subclasses that need to execute additional code after a new step has taken place. The animation step is provided for use in cases where the action depends on its value.

`[virtual protected]` void QGraphicsItemAnimation::beforeAnimationStep(qreal step)

This method is meant to be overridden by subclassed that needs to execute additional code before a new step takes place. The animation step is provided for use in cases where the action depends on its value.

void QGraphicsItemAnimation::clear()

Clears the scheduled transformations used for the animation, but retains the item and timeline.

qreal QGraphicsItemAnimation::horizontalScaleAt(qreal step) const

Returns the horizontal scale for the item at the specified step value.

See also setScaleAt().

qreal QGraphicsItemAnimation::horizontalShearAt(qreal step) const

Returns the horizontal shear for the item at the specified step value.

See also setShearAt().

QGraphicsItem *QGraphicsItemAnimation::item() const

Returns the item on which the animation object operates.

See also setItem().

QPointF QGraphicsItemAnimation::posAt(qreal step) const

Returns the position of the item at the given step value.

See also setPosAt().

QList<QPair<qreal, QPointF>> QGraphicsItemAnimation::posList() const

Returns all explicitly inserted positions.

See also posAt() and setPosAt().

qreal QGraphicsItemAnimation::rotationAt(qreal step) const

Returns the angle at which the item is rotated at the specified step value.

See also setRotationAt().

QList<QPair<qreal, qreal>> QGraphicsItemAnimation::rotationList() const

Returns all explicitly inserted rotations.

See also rotationAt() and setRotationAt().

QList<QPair<qreal, QPointF>> QGraphicsItemAnimation::scaleList() const

Returns all explicitly inserted scales.

See also verticalScaleAt(), horizontalScaleAt(), and setScaleAt().

void QGraphicsItemAnimation::setItem(QGraphicsItem **item*)

Sets the specified item to be used in the animation.

See also item().

void QGraphicsItemAnimation::setPosAt(qreal step, const QPointF &point)

Sets the position of the item at the given step value to the point specified.

See also posAt().

void QGraphicsItemAnimation::setRotationAt(qreal step, qreal angle)

Sets the rotation of the item at the given step value to the angle specified.

See also rotationAt().

void QGraphicsItemAnimation::setScaleAt(qreal step, qreal sx, qreal sy)

Sets the scale of the item at the given step value using the horizontal and vertical scale factors specified by sx and sy.

See also verticalScaleAt() and horizontalScaleAt().

void QGraphicsItemAnimation::setShearAt(qreal step, qreal sh, qreal sv)

Sets the shear of the item at the given step value using the horizontal and vertical shear factors specified by sh and sv.

See also verticalShearAt() and horizontalShearAt().

void QGraphicsItemAnimation::setTimeLine(QTimeLine **timeLine*)

Sets the timeline object used to control the rate of animation to the timeLine specified.

See also timeLine().

void QGraphicsItemAnimation::setTranslationAt(qreal step, qreal dx, qreal dy)

Sets the translation of the item at the given step value using the horizontal and vertical coordinates specified by dx and dy.

See also xTranslationAt() and yTranslationAt().

QList<QPair<qreal, QPointF>> QGraphicsItemAnimation::shearList() const

Returns all explicitly inserted shears.

See also verticalShearAt(), horizontalShearAt(), and setShearAt().

QTimeLine *QGraphicsItemAnimation::timeLine() const

Returns the timeline object used to control the rate at which the animation occurs.

See also setTimeLine().

QTransform QGraphicsItemAnimation::transformAt(qreal step) const

Returns the transform used for the item at the specified step value.

This function was introduced in Qt 5.14.

QList<QPair<qreal, QPointF>> QGraphicsItemAnimation::translationList() const

Returns all explicitly inserted translations.

See also xTranslationAt(), yTranslationAt(), and setTranslationAt().

qreal QGraphicsItemAnimation::verticalScaleAt(qreal step) const

Returns the vertical scale for the item at the specified step value.