path: root/doc/src/declarative/animation.qdoc

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/*!
\page qdeclarativeanimation.html
\ingroup qml-features
\contentspage QML Features
\previouspage {QML States}{States}
\nextpage {QML Data Models}{Structuring Data with Models}
\title QML Animation and Transitions

\keyword qml-animation-elements
\section1 Animation and Transitions Elements
\list
\o \l {Transition} - Animates transitions during state changes
\o \l {SequentialAnimation} - Runs animations sequentially
\o \l {ParallelAnimation} - Runs animations in parallel
\o \l {Behavior} - Specifies a default animation for property changes
\o \l {PropertyAction} - Sets immediate property changes during animation
\o \l {PauseAnimation} - Introduces a pause in an animation
\o \l {SmoothedAnimation} - Allows a property to smoothly track a value
\o \l {SpringAnimation} - Allows a property to track a value in a spring-like motion
\o \l {ScriptAction} - Runs scripts during an animation
\endlist

\keyword qml-property-animation-elements
Elements that animate properties based on data types
\list
\o \l {PropertyAnimation} - Animates property changes
\o \l {NumberAnimation} - Animates properties of type qreal
\o \l {Vector3dAnimation} - Animates properties of type QVector3d
\o \l {ColorAnimation} - Animates color changes
\o \l {RotationAnimation} - Animates rotations
\o \l {ParentAnimation} - Animates parent changes
\o \l {AnchorAnimation} - Animates anchor changes
\endlist

In QML, animations are created by applying animation elements to property
values. Animation elements will interpolate property values to create smooth
transitions. As well, state transitions may assign animations to state changes.

To create an animation, use an appropriate animation element for the type of
the property that is to be animated, and apply the animation depending on the
type of behavior that is required.

\keyword qml-triggering-animations
\section1 Triggering Animations

There are several ways of setting animation to an object.

\keyword qml-direct-animation
\section2 Direct Property Animation

To create an immediate movement or animated movement, set the property value
directly. This may be done in signal handlers or attached properties.

\snippet doc/src/snippets/declarative/animation.qml direct property change

However, to create more control, \e {property animations} apply smooth movements
by interpolating values between property value changes. Property animations
provide timing controls and allows different interpolations through
\l{qml-easing-animation}{easing curves}.

\snippet doc/src/snippets/declarative/animation.qml property animation

Specialized \l{qml-property-animation-elements}{property animation elements}
have more efficient implementations than the \l{PropertyAnimation} element. They
are for setting animations to different QML types such as \c int, \c color, and
rotations. Similarly, the \l{ParentAnimation} can animate parent changes.

See the \l {qml-controlling-animations}{Controlling Animations} section for more
information about the different animation properties.

\keyword qml-transition-animations
\section2 Transitions during State Changes

\l{QML States}{States} are property configurations where a property may have different values to reflect different states. State changes introduce
abrupt property changes; animations smooth transitions to produce visually
appealing state changes.

The \l{Transition} element can contain
\l{qml-animation-elements}{animation elements} to interpolate property changes
caused by state changes. To assign the transition to an object, bind it to the
\c transitions property.

A button might have two states, the \c pressed state when the user clicks on the
button and a \c released state when the user releases the button. We can assign
different property configurations for each state. A transition would animate the
change from the \c pressed state to the \c released state. Likewise, there would
be an animation during the change from the \c released state to the \c pressed
state.

\snippet doc/src/snippets/declarative/animation.qml transition animation

Binding the \c to and \c from properties to the state's name will assign that
particular transition to the state change. For simple or symmetric transitions,
setting the to \c to property to the wild card symbol, "\c{*}", denotes
that the transition applies to any state change.

\snippet doc/src/snippets/declarative/animation.qml wildcard animation

\section2 Default Animation as Behaviors

Default property animations are set using \e {behavior animations}. Animations
declared in \l {Behavior} elements apply to the property and animates any
property value changes. However, Behavior elements have an
\c enabled property to purposely enable or disable the behavior animations.

A ball component might have a behavior animation assigned to its \c x, \c y, and
\c color properties. The behavior animation could be set up to simulate an
elastic effect. In effect, this behavior animation would apply the elastic
effect to the properties whenever the ball moves.

\snippet doc/src/snippets/declarative/animation.qml behavior animation

There are several methods of assigning behavior animations to properties. The
\c{Behavior on <property>} declaration is a convenient way of assigning a
behavior animation onto a property.

See the \l {declarative/animation/behaviors}{Behaviors example} for a
demonstration of behavioral animations.

\section1 Playing Animations in Parallel or in Sequence

Animations can run \e {in parallel} or \e {in sequence}. Parallel animations
will play a group of animations at the same time while sequential animations
play a group of animations in order: one after the other. Grouping animations in
\l{SequentialAnimation} and \l{ParallelAnimation} will play the animations in
sequence or in parallel.

A banner component may have several icons or slogans to display, one after the
other. The \c opacity property could transform to \c 1.0 denoting an opaque
object. Using the \l{SequentialAnimation} element, the opacity animations will
play after the preceding animation finishes. The \l{ParallelAnimation} element
will play the animations at the same time.

\snippet doc/src/snippets/declarative/animation.qml sequential animation

Once individual animations are placed into a SequentialAnimation or
ParallelAnimation, they can no longer be started and stopped independently. The
sequential or parallel animation must be started and stopped as a group.

The \l SequentialAnimation element is also useful for playing
\l{qml-transition-animations}{transition animations} because animations are
played in parallel inside transitions.

See the \l {declarative/animation/basics}{Animation basics example} for a
demonstration of creating and combining multiple animations in QML.

\keyword qml-controlling-animations
\section1 Controlling Animations

There are different methods to control animations.

\section2 Animation Playback
All \l{qml-animation-elements}{animation elements} inherit from the \l Animation element. It is not
possible to create \l Animation objects; instead, this element provides the
essential properties and methods for animation elements. Animation elements have
\c{start()}, \c{stop()}, \c{resume()}, \c{pause()}, \c {restart()}, and
\c{complete()} -- all of these methods control the execution of animations.

\keyword qml-easing-animation
\section2 Easing

Easing curves define how the animation will interpolate between the start value
and the end value. Different easing curves might go beyond the defined range of
interpolation. The easing curves simplify the creation of animation effects such
as bounce effects, acceleration, deceleration, and cyclical animations.

A QML object may have different easing curve for each property animation. There
are also different parameters to control the curve, some of which are exclusive
to a particular curve. For more information about the easing curves, visit the
\l {PropertyAnimation::easing.type}{easing} documentation.

The \l{declarative/animation/easing}{easing example} visually demonstrates each
of the different easing types.

\section2 Other Animation Elements

In addition, QML provides several other elements useful for animation:

\list
\o PauseAnimation: enables pauses during animations
\o ScriptAction: allows JavaScript to be executed during an animation, and can
be used together with StateChangeScript to reused existing scripts
\o PropertyAction: changes a property \e immediately during an animation,
without animating the property change
\endlist

These are specialized animation elements that animate different property types
\list
\o SmoothedAnimation: a specialized NumberAnimation that provides smooth
changes in animation when the target value changes
\o SpringAnimation: provides a spring-like animation with specialized
attributes such as \l {SpringAnimation::}{mass},
\l{SpringAnimation::}{damping} and \l{SpringAnimation::}{epsilon}
\o ParentAnimation: used for animating a parent change (see ParentChange)
\o AnchorAnimation: used for animating an anchor change (see AnchorChanges)
\endlist

*/



\snippet doc/src/snippets/declarative/animation-elements.qml color
\snippet doc/src/snippets/declarative/animation-propertyvaluesource.qml 0
\snippet doc/src/snippets/declarative/animation-signalhandler.qml 0
\snippet doc/src/snippets/declarative/animation-standalone.qml 0

\snippet doc/src/snippets/declarative/animation-transitions.qml 0
\snippet doc/src/snippets/declarative/animation-groups.qml 0

\snippet doc/src/snippets/declarative/animation-groups.qml 1
\snippet doc/src/snippets/declarative/animation-groups.qml 0
\image propanim.gif