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QML PropertyAnimation Element

The PropertyAnimation element animates changes in property values. More...

Inherits Animation

Inherited by ColorAnimation, NumberAnimation, RotationAnimation, and Vector3dAnimation.

This element was introduced in Qt 4.7.

Properties

Detailed Description

PropertyAnimation provides a way to animate changes to a property's value.

It can be used to define animations in a number of ways:

  • In a Transition

    For example, to animate any objects that have changed their x or y properties as a result of a state change, using an InOutQuad easing curve:

     Rectangle {
     id: rect
     width: 100; height: 100
     color: "red"

     states: State {
         name: "moved"
         PropertyChanges { target: rect; x: 50 }
     }

     transitions: Transition {
         PropertyAnimation { properties: "x,y"; easing.type: Easing.InOutQuad }
     }
 }
  • In a Behavior

    For example, to animate all changes to a rectangle's x property:

     Rectangle {
     width: 100; height: 100
     color: "red"

     Behavior on x { PropertyAnimation {} }

     MouseArea { anchors.fill: parent; onClicked: parent.x = 50 }
 }
  • As a property value source

    For example, to repeatedly animate the rectangle's x property:

     Rectangle {
     width: 100; height: 100
     color: "red"

     SequentialAnimation on x {
         loops: Animation.Infinite
         PropertyAnimation { to: 50 }
         PropertyAnimation { to: 0 }
     }
 }
  • In a signal handler

    For example, to fade out theObject when clicked:

     MouseArea {
     anchors.fill: theObject
     onClicked: PropertyAnimation { target: theObject; property: "opacity"; to: 0 }
 }
  • Standalone

    For example, to animate rect's width property over 500ms, from its current width to 30:

     Rectangle {
     id: theRect
     width: 100; height: 100
     color: "red"

     // this is a standalone animation, it's not running by default
     PropertyAnimation { id: animation; target: theRect; property: "width"; to: 30; duration: 500 }

     MouseArea { anchors.fill: parent; onClicked: animation.running = true }
 }

Depending on how the animation is used, the set of properties normally used will be different. For more information see the individual property documentation, as well as the QML Animation and Transitions introduction.

Note that PropertyAnimation inherits the abstract Animation element. This includes additional properties and methods for controlling the animation.

See also QML Animation and Transitions and Animation basics example.

Property Documentation

duration : int

This property holds the duration of the animation, in milliseconds.

The default value is 250.


easing.type : enumeration

easing.amplitude : real

easing.overshoot : real

easing.period : real

To specify an easing curve you need to specify at least the type. For some curves you can also specify amplitude, period and/or overshoot (more details provided after the table). The default easing curve is Easing.Linear.

 PropertyAnimation { properties: "y"; easing.type: Easing.InOutElastic; easing.amplitude: 2.0; easing.period: 1.5 }

Available types are:

Easing.Linear Easing curve for a linear (t) function: velocity is constant.
Easing.InQuad Easing curve for a quadratic (t^2) function: accelerating from zero velocity.
Easing.OutQuad Easing curve for a quadratic (t^2) function: decelerating to zero velocity.
Easing.InOutQuad Easing curve for a quadratic (t^2) function: acceleration until halfway, then deceleration.
Easing.OutInQuad Easing curve for a quadratic (t^2) function: deceleration until halfway, then acceleration.
Easing.InCubic Easing curve for a cubic (t^3) function: accelerating from zero velocity.
Easing.OutCubic Easing curve for a cubic (t^3) function: decelerating from zero velocity.
Easing.InOutCubic Easing curve for a cubic (t^3) function: acceleration until halfway, then deceleration.
Easing.OutInCubic Easing curve for a cubic (t^3) function: deceleration until halfway, then acceleration.
Easing.InQuart Easing curve for a quartic (t^4) function: accelerating from zero velocity.
Easing.OutQuart Easing curve for a quartic (t^4) function: decelerating from zero velocity.
Easing.InOutQuart Easing curve for a quartic (t^4) function: acceleration until halfway, then deceleration.
Easing.OutInQuart Easing curve for a quartic (t^4) function: deceleration until halfway, then acceleration.
Easing.InQuint Easing curve for a quintic (t^5) function: accelerating from zero velocity.
Easing.OutQuint Easing curve for a quintic (t^5) function: decelerating from zero velocity.
Easing.InOutQuint Easing curve for a quintic (t^5) function: acceleration until halfway, then deceleration.
Easing.OutInQuint Easing curve for a quintic (t^5) function: deceleration until halfway, then acceleration.
Easing.InSine Easing curve for a sinusoidal (sin(t)) function: accelerating from zero velocity.
Easing.OutSine Easing curve for a sinusoidal (sin(t)) function: decelerating from zero velocity.
Easing.InOutSine Easing curve for a sinusoidal (sin(t)) function: acceleration until halfway, then deceleration.
Easing.OutInSine Easing curve for a sinusoidal (sin(t)) function: deceleration until halfway, then acceleration.
Easing.InExpo Easing curve for an exponential (2^t) function: accelerating from zero velocity.
Easing.OutExpo Easing curve for an exponential (2^t) function: decelerating from zero velocity.
Easing.InOutExpo Easing curve for an exponential (2^t) function: acceleration until halfway, then deceleration.
Easing.OutInExpo Easing curve for an exponential (2^t) function: deceleration until halfway, then acceleration.
Easing.InCirc Easing curve for a circular (sqrt(1-t^2)) function: accelerating from zero velocity.
Easing.OutCirc Easing curve for a circular (sqrt(1-t^2)) function: decelerating from zero velocity.
Easing.InOutCirc Easing curve for a circular (sqrt(1-t^2)) function: acceleration until halfway, then deceleration.
Easing.OutInCirc Easing curve for a circular (sqrt(1-t^2)) function: deceleration until halfway, then acceleration.
Easing.InElastic Easing curve for an elastic (exponentially decaying sine wave) function: accelerating from zero velocity.
The peak amplitude can be set with the amplitude parameter, and the period of decay by the period parameter.
Easing.OutElastic Easing curve for an elastic (exponentially decaying sine wave) function: decelerating from zero velocity.
The peak amplitude can be set with the amplitude parameter, and the period of decay by the period parameter.
Easing.InOutElastic Easing curve for an elastic (exponentially decaying sine wave) function: acceleration until halfway, then deceleration.
Easing.OutInElastic Easing curve for an elastic (exponentially decaying sine wave) function: deceleration until halfway, then acceleration.
Easing.InBack Easing curve for a back (overshooting cubic function: (s+1)*t^3 - s*t^2) easing in: accelerating from zero velocity.
Easing.OutBack Easing curve for a back (overshooting cubic function: (s+1)*t^3 - s*t^2) easing out: decelerating to zero velocity.
Easing.InOutBack Easing curve for a back (overshooting cubic function: (s+1)*t^3 - s*t^2) easing in/out: acceleration until halfway, then deceleration.
Easing.OutInBack Easing curve for a back (overshooting cubic easing: (s+1)*t^3 - s*t^2) easing out/in: deceleration until halfway, then acceleration.
Easing.InBounce Easing curve for a bounce (exponentially decaying parabolic bounce) function: accelerating from zero velocity.
Easing.OutBounce Easing curve for a bounce (exponentially decaying parabolic bounce) function: decelerating from zero velocity.
Easing.InOutBounce Easing curve for a bounce (exponentially decaying parabolic bounce) function easing in/out: acceleration until halfway, then deceleration.
Easing.OutInBounce Easing curve for a bounce (exponentially decaying parabolic bounce) function easing out/in: deceleration until halfway, then acceleration.

easing.amplitude is only applicable for bounce and elastic curves (curves of type Easing.InBounce, Easing.OutBounce, Easing.InOutBounce, Easing.OutInBounce, Easing.InElastic, Easing.OutElastic, Easing.InOutElastic or Easing.OutInElastic).

easing.overshoot is only applicable if easing.type is: Easing.InBack, Easing.OutBack, Easing.InOutBack or Easing.OutInBack.

easing.period is only applicable if easing.type is: Easing.InElastic, Easing.OutElastic, Easing.InOutElastic or Easing.OutInElastic.

See the easing example for a demonstration of the different easing settings.


read-onlyexclude : list<Object>

This property holds the items not to be affected by this animation.

See also PropertyAnimation::targets.


from : real

This property holds the starting value for the animation.

If the PropertyAnimation is defined within a Transition or Behavior, this value defaults to the value defined in the starting state of the Transition, or the current value of the property at the moment the Behavior is triggered.

See also QML Animation and Transitions.


properties : string

targets : list<Object>

property : string

target : Object

These properties are used as a set to determine which properties should be animated. The singular and plural forms are functionally identical, e.g.

 NumberAnimation { target: theItem; property: "x"; to: 500 }

has the same meaning as

 NumberAnimation { targets: theItem; properties: "x"; to: 500 }

The singular forms are slightly optimized, so if you do have only a single target/property to animate you should try to use them.

The targets property allows multiple targets to be set. For example, this animates the x property of both itemA and itemB:

 NumberAnimation { targets: [itemA, itemB]; properties: "x"; to: 500 }

In many cases these properties do not need to be explicitly specified, as they can be inferred from the animation framework:

Value Source / Behavior When an animation is used as a value source or in a Behavior, the default target and property name to be animated can both be inferred. 
    Rectangle {
        id: theRect
        width: 100; height: 100
        color: Qt.rgba(0,0,1)
        NumberAnimation on x { to: 500; loops: Animation.Infinite } //animate theRect's x property
        Behavior on y { NumberAnimation {} } //animate theRect's y property
    }
Transition When used in a transition, a property animation is assumed to match all targets but no properties. In practice, that means you need to specify at least the properties in order for the animation to do anything. 
    Rectangle {
        id: theRect
        width: 100; height: 100
        color: Qt.rgba(0,0,1)
        Item { id: uselessItem }
        states: State {
            name: "state1"
            PropertyChanges { target: theRect; x: 200; y: 200; z: 4 }
            PropertyChanges { target: uselessItem; x: 10; y: 10; z: 2 }
        }
        transitions: Transition {
            //animate both theRect's and uselessItem's x and y to their final values
            NumberAnimation { properties: "x,y" }

            //animate theRect's z to its final value
            NumberAnimation { target: theRect; property: "z" }
        }
    }
Standalone When an animation is used standalone, both the target and property need to be explicitly specified. 
    Rectangle {
        id: theRect
        width: 100; height: 100
        color: Qt.rgba(0,0,1)
        //need to explicitly specify target and property
        NumberAnimation { id: theAnim; target: theRect; property: "x"; to: 500 }
        MouseArea {
            anchors.fill: parent
            onClicked: theAnim.start()
        }
    }

As seen in the above example, properties is specified as a comma-separated string of property names to animate.

See also exclude and QML Animation and Transitions.


to : real

This property holds the end value for the animation.

If the PropertyAnimation is defined within a Transition or Behavior, this value defaults to the value defined in the end state of the Transition, or the value of the property change that triggered the Behavior.

See also QML Animation and Transitions.


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