QPropertyAnimation Class

Detailed Description

QPropertyAnimation interpolates over Qt properties. As property values are stored in QVariants, the class inherits QVariantAnimation, and supports animation of the same meta types as its super class.

A class declaring properties must be a QObject. To make it possible to animate a property, it must provide a setter (so that QPropertyAnimation can set the property's value). Note that this makes it possible to animate many of Qt's widgets. Let's look at an example:

 #include <QApplication>
 #include <QPushButton>
 #include <QPropertyAnimation>

 class MyButtonWidget : public QWidget
 {
 public:
     MyButtonWidget(QWidget *parent = nullptr);
 };

 MyButtonWidget::MyButtonWidget(QWidget *parent) : QWidget(parent)
 {
     QPushButton *button = new QPushButton(tr("Animated Button"), this);
     QPropertyAnimation *anim = new QPropertyAnimation(button, "pos", this);
     anim->setDuration(10000);
     anim->setStartValue(QPoint(0, 0));
     anim->setEndValue(QPoint(100, 250));
     anim->start();
 }

 int main(int argc, char *argv[])
 {
     QApplication a(argc, argv);
     MyButtonWidget buttonAnimWidget;
     buttonAnimWidget.resize(QSize(800, 600));
     buttonAnimWidget.show();
     return a.exec();
 }

The property name and the QObject instance of which property should be animated are passed to the constructor. You can then specify the start and end value of the property. The procedure is equal for properties in classes you have implemented yourself–just check with QVariantAnimation that your QVariant type is supported.

The QVariantAnimation class description explains how to set up the animation in detail. Note, however, that if a start value is not set, the property will start at the value it had when the QPropertyAnimation instance was created.

QPropertyAnimation works like a charm on its own. For complex animations that, for instance, contain several objects, QAnimationGroup is provided. An animation group is an animation that can contain other animations, and that can manage when its animations are played. Look at QParallelAnimationGroup for an example.