QVariantAnimation

The QVariantAnimation class provides a base class for animations. More

Inheritance diagram of PySide2.QtCore.QVariantAnimation

Inherited by: QPropertyAnimation

New in version 4.6.

Synopsis

Functions

Virtual functions

Signals

Detailed Description

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

The class performs interpolation over QVariant s, 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 or connect to said signal.

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 QVariant s are interpolated by creating a subclass of QVariantAnimation , and reimplementing the virtual interpolated() function.

Subclassing QVariantAnimation can be an alternative if you have QVariant s 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

  • UInt

  • 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.

class PySide2.QtCore.QVariantAnimation([parent=None])
param parent

PySide2.QtCore.QObject

Construct a QVariantAnimation object. parent is passed to QAbstractAnimation ‘s constructor.

PySide2.QtCore.QVariantAnimation.currentValue()
Return type

object

This property holds the current value of the animation..

This property describes the current value; an interpolated value between the start value and the end value , using the current time for progress. The value itself is obtained from interpolated() , which is called repeatedly as the animation is running.

QVariantAnimation calls the virtual updateCurrentValue() function when the current value changes. This is particularly useful for subclasses that need to track updates. For example, QPropertyAnimation uses this function to animate Qt properties .

See also

startValue endValue

PySide2.QtCore.QVariantAnimation.easingCurve()
Return type

PySide2.QtCore.QEasingCurve

This property holds the easing curve of the animation.

This property defines the easing curve of the animation. By default, a linear easing curve is used, resulting in linear interpolation. Other curves are provided, for instance, InCirc , which provides a circular entry curve. Another example is InOutElastic , which provides an elastic effect on the values of the interpolated variant.

QVariantAnimation will use the valueForProgress() to transform the “normalized progress” ( currentTime / totalDuration ) of the animation into the effective progress actually used by the animation. It is this effective progress that will be the progress when interpolated() is called. Also, the steps in the keyValues are referring to this effective progress.

The easing curve is used with the interpolator, the interpolated() virtual function, and the animation’s duration to control how the current value changes as the animation progresses.

PySide2.QtCore.QVariantAnimation.endValue()
Return type

object

This property holds the end value of the animation.

This property describes the end value of the animation.

See also

startValue

PySide2.QtCore.QVariantAnimation.interpolated(from, to, progress)
Parameters
  • from – object

  • to – object

  • progress – float

Return type

object

This virtual function returns the linear interpolation between variants from and to , at progress , usually a value between 0 and 1. You can reimplement this function in a subclass of QVariantAnimation to provide your own interpolation algorithm.

Note that in order for the interpolation to work with a QEasingCurve that return a value smaller than 0 or larger than 1 (such as InBack ) you should make sure that it can extrapolate. If the semantic of the datatype does not allow extrapolation this function should handle that gracefully.

You should call the QVariantAnimation implementation of this function if you want your class to handle the types already supported by Qt (see class QVariantAnimation description for a list of supported types).

See also

QEasingCurve

PySide2.QtCore.QVariantAnimation.keyValueAt(step)
Parameters

step – float

Return type

object

Returns the key frame value for the given step . The given step must be in the range 0 to 1. If there is no KeyValue for step , it returns an invalid QVariant .

PySide2.QtCore.QVariantAnimation.keyValues()
Return type

Returns the key frames of this animation.

PySide2.QtCore.QVariantAnimation.setDuration(msecs)
Parameters

msecs – int

This property holds the duration of the animation.

This property describes the duration in milliseconds of the animation. The default duration is 250 milliseconds.

See also

duration()

PySide2.QtCore.QVariantAnimation.setEasingCurve(easing)
Parameters

easingPySide2.QtCore.QEasingCurve

This property holds the easing curve of the animation.

This property defines the easing curve of the animation. By default, a linear easing curve is used, resulting in linear interpolation. Other curves are provided, for instance, InCirc , which provides a circular entry curve. Another example is InOutElastic , which provides an elastic effect on the values of the interpolated variant.

QVariantAnimation will use the valueForProgress() to transform the “normalized progress” ( currentTime / totalDuration ) of the animation into the effective progress actually used by the animation. It is this effective progress that will be the progress when interpolated() is called. Also, the steps in the keyValues are referring to this effective progress.

The easing curve is used with the interpolator, the interpolated() virtual function, and the animation’s duration to control how the current value changes as the animation progresses.

PySide2.QtCore.QVariantAnimation.setEndValue(value)
Parameters

value – object

This property holds the end value of the animation.

This property describes the end value of the animation.

See also

startValue

PySide2.QtCore.QVariantAnimation.setKeyValueAt(step, value)
Parameters
  • step – float

  • value – object

Creates a key frame at the given step with the given value . The given step must be in the range 0 to 1.

PySide2.QtCore.QVariantAnimation.setKeyValues(values)
Parameters

values

Replaces the current set of key frames with the given keyValues . the step of the key frames must be in the range 0 to 1.

PySide2.QtCore.QVariantAnimation.setStartValue(value)
Parameters

value – object

This property holds the optional start value of the animation.

This property describes the optional start value of the animation. If omitted, or if a null QVariant is assigned as the start value, the animation will use the current position of the end when the animation is started.

See also

endValue

PySide2.QtCore.QVariantAnimation.startValue()
Return type

object

This property holds the optional start value of the animation.

This property describes the optional start value of the animation. If omitted, or if a null QVariant is assigned as the start value, the animation will use the current position of the end when the animation is started.

See also

endValue

PySide2.QtCore.QVariantAnimation.updateCurrentValue(value)
Parameters

value – object

This virtual function is called every time the animation’s current value changes. The value argument is the new current value.

The base class implementation does nothing.

See also

currentValue

PySide2.QtCore.QVariantAnimation.valueChanged(value)
Parameters

value – object