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diff --git a/doc/src/declarative/animation.qdoc b/doc/src/declarative/animation.qdoc index 401cf16..7416341 100644 --- a/doc/src/declarative/animation.qdoc +++ b/doc/src/declarative/animation.qdoc @@ -29,134 +29,301 @@ \page qdeclarativeanimation.html \title QML Animation -Animation in QML is done by animating properties of objects. Properties of type -real, int, color, rect, point, size, and vector3d can all be animated. -QML supports three main forms of animation: basic property animation, -transitions, and property behaviors. +In QML, animations are created by applying animation objects to object property +values to gradually change them over time. Animation objects are created from +the built-in set of animation elements, which can be used to animate various +types of property values. In addition, animation objects can be applied in +different ways depending on the context in which they are required. + +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. This page describes the \l {Types of +Animations} that can be created and the \l {Animation Elements} that are used +to create these animations. + + +\section1 Types of Animations + +An animation is created in different ways depending on the context in which it +is required. Suppose a \l Rectangle's movement - that is, changes in its \c x +or \c y property values - should be animated. The semantics of the animation +differ depending on whether you want to create: + +\list +\o An animation that moves the \l Rectangle as soon as it is created, to a +known position +\o An animation that only triggers when the \l Rectangle is moved by external +sources - for example, when the mouse is clicked, animate the movement to the +mouse position +\o An animation that triggers when a particular signal is received +\o A standalone animation that is not bound to the \l Rectangle's movement, but +instead can be started and stopped from script as required +\o An animation that only triggers during \l{QML States}{state changes} +\endlist + +To support these different types of animation methods, QML provides several +methods for defining an animation. These are: + +\list +\o Creating an \l{Animations as Property Value Sources}{animation using +property value sources}, to immediately animate a specific property +\o Using \l{Behavioral Animations}{behavioral animations}, which are triggered +when a property changes value +\o \l{Animations in a Signal Handler}{Within a signal handler}, to be triggered +when a signal is received +\o As a \l{Standalone Animation}{standalone animation}, that can be +started/stopped from script and can be rebound to different objects +\o Using \l{Transitions}{transitions}, to provide animations between \l{QML +States}{state changes} +\endlist + +These methods are demonstrated below. Notice these examples use +PropertyAnimation, which is one of several QML elements that can be used to +create an animation. See the \l {Animation Elements} section further below for +details. -\tableofcontents -\section1 Basic Property Animation -The simplest form of animation is a \l PropertyAnimation, which can animate all of the property -types listed above. If the property you are animating is a number or color, you can alternatively use -NumberAnimation or ColorAnimation. These elements don't add any additional functionality, -but will help enforce type correctness and are slightly more efficient. +\section2 Animations as Property Value Sources + +An animation is applied as a \l{QDeclarativePropertyValueSource}{property value +source} using the \e Animation \bold on \e Property syntax. Here is a \l +Rectangle whose movement is animated using this method: + +\snippet doc/src/snippets/declarative/animation-propertyvaluesource.qml 0 + +This applies a PropertyAnimation to the \l Rectangle's \c x and \c y properties +to animate from their current values (i.e. zero) to 50, over 1000 milliseconds. +The animation starts as soon as the \l Rectangle is loaded. To animate from +specific values rather than the current \c x and \c y values, set the +PropertyAnimation's \l {PropertyAnimation::}{from} property. + +Specifying an animation as a property value source is useful for animating a +property to a particular value as soon as the object is loaded. + + +\section2 Behavioral Animations + +Often an animation should be applied whenever a particular property value +changes. In these cases, a \l Behavior can be used to specify a default +animation for a property change. Here is an example: + +\snippet doc/src/snippets/declarative/animation-behavioral.qml 0 -A property animation can be specified as a value source using the \e Animation \bold on \e property syntax. This is especially useful -for repeating animations. +This \l Rectangle has \l Behavior objects applied to its \c x and \c y +properties. Whenever these properties change (in this case, when the mouse is +clicked within the parent \l Item), the PropertyAnimation objects defined +within the behaviors will be applied to these properties, thus animating the \l +Rectangle's movement to its new position. Unlike the method of \l {Animations +as Property Value Sources}{defining an animation as a property value source}, +which creates a one-time animation that animates a property to a known value, a +behavioral animation is an animation that is triggered \e {in response to} a +value change. -The following example creates a bouncing effect: -\snippet doc/src/snippets/declarative/animation.qml property-anim-1 +Any changes to these properties will trigger their animations. If \c x or \c y +were bound to other properties, and those properties changed, the animation +would be triggered. The \l{Behavior::}{enabled} property can be used to force a +\l Behavior to only apply under certain circumstances. -\image propanim.gif +Notice that unlike for property value source animations, the +PropertyAnimation's \l {PropertyAnimation::}{from} and \l +{PropertyAnimation::}{to} properties do not need to be defined because these +values are already provided, respectively, by the \l Rectangle's current values +and the new values set in the \c onClicked handler. If these properties were +defined anyway, they would override the default values. + +See the \l {declarative/animation/behaviors}{Behaviors example} for a +demonstration of behavioral animations. + + +\section2 Animations in a Signal Handler + +An animation can be created within a signal handler to be triggered when the +signal is received. For example: + +\snippet doc/src/snippets/declarative/animation-signalhandler.qml 0 + +The PropertyAnimation is triggered when the MouseArea is clicked, animating the +\c x and \c y properties to a value of 50 over 1000 milliseconds. Since the +animation is not bound to a particular object or property, it must define the +\l {PropertyAnimation::}{target} and \l {PropertyAnimation::}{property} (or \l +{PropertyAnimation::}{targets} and \l{PropertyAnimation::}{properties}) values. +The \l {PropertyAnimation::}{to} property is also required to specify the new +\c x and \c y values. + + +\section2 Standalone Animations + +Animations can also be created as ordinary QML objects that are not bound to +any particular objects and properties. An example: + +\snippet doc/src/snippets/declarative/animation-standalone.qml 0 + +A standalone animation is not running by default and must be started explicitly +using the \l {Animation::}{running} property or \l {Animation::}{start()} and +\l {Animation::}{stop()} methods. Since the animation is not bound to a +particular object or property, it must define the \l +{PropertyAnimation::}{target} and \l {PropertyAnimation::}{property} (or \l +{PropertyAnimation::}{targets} and \l{PropertyAnimation::}{properties}) values. +The \l {PropertyAnimation::}{to} property is also required to specify the new +\c x and \c y values. (The \l {PropertyAnimation::}{from} value can optionally +be provided.) + +Standalone animations are useful when an animation is not targeted towards a +single object property and the animation should be explicitly started and +stopped. + + +\section2 Transitions -When you assign an animation as a value source, you do not need to specify \c property -or \c target values; they are automatically selected for you. You do, however, need to specify a \c to value. -An animation specified as a value source will be \c running by default. +Transitions are used to describe the animations to be applied when a \l {QML +States}{state change} occurs. To create a transition, define a \l Transition +object and add it to an item's \l {Item::}{transitions} property. An example: -For example, here is a rectangle that uses a \l NumberAnimation value source to animate the movement -from its current position to an \c x value of 50. The animation starts immediately, and only the \c to -property is required: +\snippet doc/src/snippets/declarative/animation-transitions.qml 0 -\snippet doc/src/snippets/declarative/animation.qml property-anim-2 +When the \l Rectangle changes to the \e moved state, its \c x and \c y property +values are changed by the PropertyChanges object, and the PropertyAnimation +defined within the \l Transition is triggered on these properties. The +animation will not be applied at any time other than during the state change. -A property animation can also be specified as a resource that is manipulated from script. +Notice the example does not set any \l {PropertyAnimation::}{from} and \l +{PropertyAnimation::}{to} values for the PropertyAnimation. As a convenience, +these properties are automatically set to the values of \c x and \c y before +and after the state change, respectively. However, they can be explicitly set +if these values should be overrided. -\snippet doc/src/snippets/declarative/animation.qml property-anim-3 +Also notice the PropertyAnimation does not need to specify a \l +{PropertyAnimation::}{target} object; any \c x or \c y value of any object that +has changed during the state change will be animated. However, the target can +be set if the animation should be restricted to certain objects. -As can be seen, when an animation is used like this (as opposed to as a value source) you will need -to explicitly set the \c target and \c property to animate. This also the only case where -an animation needs to be started explictly by either setting the \c running property to -true or calling the \c start() method. +The top-level animations in a \l Transition are run in parallel. To run them +one after the other, use a SequentialAnimation, as shown below in \l {Grouping +Animations}. -Animations can be joined into a group using SequentialAnimation and ParallelAnimation. +See the \l Transition documentation for more information. -See the \l {declarative/animation/basics}{Animation basics example} for a demonstration of creating and combining multiple animations in QML. -\target state-transitions -\section1 Transitions +\section1 Animation Elements -\l Transition elements describe the animations to perform when \l{qmlstates}{state} changes occur. A transition -can only be triggered by a state change. +To create an animation, choose from one of the built-in QML animation elements. +While the above examples are demonstrated using PropertyAnimation, they could +have used other elements depending on the type of the property to be animated +and whether a single or multiple animations are required. -For example, a \l Transition could describe how an item moves from its initial position to its new position: +All 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. For example, it allows +animations to be started and stopped through the \l {Animation::}{running} +property and the \l{Animation::}{start()} and \l{Animation::}{stop()} methods. +It can also define the number of \l {Animation::}{loops} for an animation. -\snippet doc/src/snippets/declarative/animation.qml transitions-1 -As can be seen, transitions make use of the same basic animation classes introduced above. -In the above example we have specified that we want to animate the \c x and \c y properties, but have not -specified the objects to animate or the \c to values. By default these values are supplied by the framework; -the animation will animate any \c targets whose \c x and \c y have changed, and the \c to values will be those -defined in the end state. You can always supply explicit values to override these implicit values when needed. +\section2 Property Animation Elements -\snippet doc/src/snippets/declarative/animation.qml transitions-2 +PropertyAnimation is the most basic animation element for animating a property. +It can be used to animate \c real, \c int, \c color, \c rect, \c point, \c size, and +\c vector3d properties. It is inherited by NumberAnimation, ColorAnimation, +RotationAnimation and Vector3dAnimation: NumberAnimation provides a more +efficient implementation for animating \c real and \c int properties, and +Vector3dAnimation does the same for \c vector3d properties. ColorAnimation +and RotationAnimation provide more specific attributes for animating color +and rotation changes. -QML transitions have selectors to determine which state changes a transition should apply to. -The following transition will only be triggered when we enter into the \c "details" state. -(The "*" value is a wildcard value that specifies the transition should be applied when changing -from \e any state to the "details" state.) +A ColorAnimation allows color values for the \l {ColorAnimation::}{from} +and \l {ColorAnimation::}{to} properties. The +following animates the rectangle's \l {Rectangle::color} property: -\code -Transition { - from: "*" - to: "details" - ... -} -\endcode +\snippet doc/src/snippets/declarative/animation-elements.qml color -Transitions can happen in parallel, in sequence, or in any combination of the two. By default, the top-level -animations in a transition will happen in parallel. The following example shows a rather complex transition -making use of both sequential and parallel animations: +RotationAnimation allows a rotation's direction to be specified. The following +animates the rectangle's \l {Item::rotation} property: -\snippet doc/src/snippets/declarative/animation.qml transitions-3 +\snippet doc/src/snippets/declarative/animation-elements.qml rotation +In addition, the following specialized animation elements are available: -See \l {declarative/animation/states}{States and Transitions example} for a simple example of how transitions can be applied. +\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 +See their respective documentation pages for more details. -\section1 Property Behaviors -A property \l {Behavior}{behavior} specifies a default animation to run whenever the property's value changes, regardless -of what caused the change. The \c enabled property can be used to force a \l Behavior -to only apply under certain circumstances. +\section3 Easing + +Any PropertyAnimation-based animations can specify \l +{PropertyAnimation::easing.type}{easing attributes} to control the +easing curve applied when a property value is animated. These control the +effect of the animation on the property value, to provide visual effects like +bounce, acceleration and deceleration. + +For example, this modified version of an \l {Animations as Property Value +Sources}{earlier example} uses \c Easing.OutBounce to create a bouncing effect +when the animation reaches its target value: + +\snippet doc/src/snippets/declarative/animation-easing.qml 0 + +The \l{declarative/animation/easing}{easing example} visually demonstrates each +of the different easing types. + +\section2 Grouping Animations + +Multiple animations can be combined into a single animation using one of the +animation group elements: ParallelAnimation or SequentialAnimation. As their +names suggest, animations in a ParallelAnimation are run at the same time, +while animations in a SequentialAnimation are run one after the other. + +To run multiple animations, define the animations within an animation group. +The following example creates a SequentialAnimation that runs three animations +one after the other: a NumberAnimation, a PauseAnimation and another +NumberAnimation. The SequentialAnimation is applied as a \l{Animations as +Property Value Sources}{property value source animation} on the image's \c y +property, so that the animation starts as soon as the image is loaded, moving +the image up and down: + +\snippet doc/src/snippets/declarative/animation-groups.qml 0 +\image propanim.gif + +Since the SequentialAnimation is applied to the \c y property, the individual +animations within the group are automatically applied to the \c y property as +well; it is not required to set their \l{PropertyAnimation::}{properties} +values to a particular property. -In the following snippet, we specify that we want the \c x position of \c redRect to be animated -whenever it changes. The animation will last 300 milliseconds and use an \l{PropertyAnimation::easing.type}{Easing.InOutQuad} easing curve. +Animation groups can be nested. Here is a rather complex animation making use +of both sequential and parallel animations: -\snippet doc/src/snippets/declarative/animation.qml behavior +\snippet doc/src/snippets/declarative/animation-groups.qml 1 -Like using an animation as a value source, when used in a \l Behavior and animation does not need to specify -a \c target or \c property. +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. -To trigger this behavior, we could enter a state that changes \c x: +See the \l {declarative/animation/basics}{Animation basics example} for a +demonstration of creating and combining multiple animations in QML. -\qml -State { - name: "myState" - PropertyChanges { - target: redRect - x: 200 - ... - } -} -\endqml -Or, update \c x from a script: -\qml -MouseArea { - .... - onClicked: redRect.x = 24; -} -\endqml +\section2 Other Animation Elements -If \c x were bound to another property, triggering the binding would also trigger the behavior. +In addition, QML provides several other elements useful for animation: -If a state change has a transition animation matching a property with a \l Behavior, the transition animation -will override the \l Behavior for that state change. +\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 -The \l {declarative/animation/behaviors}{Behaviors example} shows how behaviors can be used to provide animations. +See their respective documentation pages for more details. */ |