Archived:How to use QVariantAnimation

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Qt Quick should be used for all UI development on mobile devices. The approach described in this article (using Qt C++ for the UI) is deprecated.

This article shows how to use QVariantAnimation.

Article Metadata

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Tested with

Devices(s): Any device which supported by Qt

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Compatibility

Platform(s): Any

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Article

Keywords: Animation framework, QPropertyAnimation, QVariantAnimation

Created: gnuton (22 Dec 2010)

Last edited: hamishwillee (30 Apr 2013)

Overview

The Qt Animation framework provides QPropertyAnimation as "default" animator for QObject derived classes. The framework provides also a lower level class: QVariantAnimation. QVariantAnimation cannot be used as it is, since it defines QVariantAnimation::updateCurrentValue as virtual. Since QGraphicsItems are not QObjects, they don't have any qobject property; in this case QVariantAnimation could be used to animate these kind of items directly and avoid subclassing the graphics item itself.

Code

Here is a simple and generic myVariantAnimator class, which emits valueChanged when the value is changed.

#ifndef MYVARIANTANIMATOR_H
#define MYVARIANTANIMATOR_H
#include <QVariantAnimation>
 
class myVariantAnimator : public QVariantAnimation
{
    Q_OBJECT
public:
     myVariantAnimator(){};
 
     virtual ~myVariantAnimator(){};
 
     void updateCurrentValue(const QVariant &value){
         emit valueChanged(value);
     }
};
 
#endif // MYVARIANTANIMATOR_H

The previous class can be used as follows:

animator.setStartValue(0);
animator.setEndValue(90);
animator.setDuration(500);
animator.setEasingCurve(QEasingCurve::OutQuart);
connect(myVariantAnimator, SIGNAL(valueChanged(const QVariant&)), rcvObj, SLOT(doAnimation()));

In this case, rcvObj::doAnimation will be called as soon as myVariantAnimator::valueChanged is emitted. doAnimation() will be able to animate several items and it's not a problem if it's not a graphics item method.

For more information see: The Animation Framework