QVariantAnimation Class

Detailed Description

The QVariantAnimation class provides an abstract base class for animations.

This class is part of The Animation Framework. It serves as a base class for property and item animations, with functions for shared functionality.

QVariantAnimation cannot be used directly as it is an abstract class; it has a pure virtual method called updateCurrentValue(). The class performs interpolation over QVariants, but leaves using the interpolated values to its subclasses. Currently, Qt provides QPropertyAnimation, which animates Qt properties. See the QPropertyAnimation class description if you wish to animate such properties.

You can then set start and end values for the property by calling setStartValue() and setEndValue(), and finally call start() to start the animation. QVariantAnimation will interpolate the property of the target object and emit valueChanged(). To react to a change in the current value you have to reimplement the updateCurrentValue() virtual function.

It is also possible to set values at specified steps situated between the start and end value. The interpolation will then touch these points at the specified steps. Note that the start and end values are defined as the key values at 0.0 and 1.0.

There are two ways to affect how QVariantAnimation interpolates the values. You can set an easing curve by calling setEasingCurve(), and configure the duration by calling setDuration(). You can change how the QVariants are interpolated by creating a subclass of QVariantAnimation, and reimplementing the virtual interpolated() function.

Subclassing QVariantAnimation can be an alternative if you have QVariants that you do not wish to declare as Qt properties. Note, however, that you in most cases will be better off declaring your QVariant as a property.

Not all QVariant types are supported. Below is a list of currently supported QVariant types:

• Int
• Double
• Float
• QLine
• QLineF
• QPoint
• QPointF
• QSize
• QSizeF
• QRect
• QRectF
• QColor

If you need to interpolate other variant types, including custom types, you have to implement interpolation for these yourself. To do this, you can register an interpolator function for a given type. This function takes 3 parameters: the start value, the end value and the current progress.

Example:

 QVariant myColorInterpolator(const QColor &start, const QColor &end, qreal progress)
 {
     ...
     return QColor(...);
 }
 ...
 qRegisterAnimationInterpolator<QColor>(myColorInterpolator);

Another option is to reimplement interpolated(), which returns interpolation values for the value being interpolated.