Detailed Description
The QGraphicsItemAnimation class provides simple animation support for QGraphicsItem.
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 The Graphics View Framework.
Member Function Documentation
QGraphicsItemAnimation::QGraphicsItemAnimation ( QObject * parent = 0 )
Constructs an animation object with the given parent.
QGraphicsItemAnimation::~QGraphicsItemAnimation () [virtual]
Destroys the animation object.
void QGraphicsItemAnimation::afterAnimationStep ( qreal step ) [virtual protected]
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.
void QGraphicsItemAnimation::beforeAnimationStep ( qreal step ) [virtual protected]
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().
QMatrix QGraphicsItemAnimation::matrixAt ( qreal step ) const
Returns the matrix used to transform the item at the specified step value.
QPointF QGraphicsItemAnimation::posAt ( qreal step ) const
Returns the position of the item at the given step value.
See also setPosAt().
void QGraphicsItemAnimation::reset () [slot]
Resets the item to its starting position and transformation.
qreal QGraphicsItemAnimation::rotationAt ( qreal step ) const
Returns the angle at which the item is rotated at the specified step value.
See also setRotationAt().
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::setStep ( qreal step ) [slot]
Sets the current step value for the animation, causing the transformations scheduled at this step to be performed.
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().
QTimeLine * QGraphicsItemAnimation::timeLine () const
Returns the timeline object used to control the rate at which the animation occurs.
See also setTimeLine().
qreal QGraphicsItemAnimation::verticalScaleAt ( qreal step ) const
Returns the vertical scale for the item at the specified step value.
See also setScaleAt().
qreal QGraphicsItemAnimation::verticalShearAt ( qreal step ) const
Returns the vertical shear for the item at the specified step value.
See also setShearAt().
qreal QGraphicsItemAnimation::xTranslationAt ( qreal step ) const
Returns the horizontal translation of the item at the specified step value.
See also setTranslationAt().
qreal QGraphicsItemAnimation::yTranslationAt ( qreal step ) const
Returns the vertical translation of the item at the specified step value.
See also setTranslationAt().
