Elements that animate properties based on data types
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.
There are several ways of setting animation to an object.
To create an immediate movement or animated movement, set the property value directly. This may be done in signal handlers or attached properties.
Rectangle { id: blob width: 75; height: 75 color: "blue" MouseArea { anchors.fill: parent onClicked: blob.color = "green" } }
However, to create more control, property animations apply smooth movements by interpolating values between property value changes. Property animations provide timing controls and allows different interpolations through easing curves .
Rectangle { id: flashingblob width: 75; height: 75 color: "blue" opacity: 1.0 MouseArea { anchors.fill: parent onClicked: { animateColor.start() animateOpacity.start() } } PropertyAnimation {id: animateColor; target: flashingblob; properties: "color"; to: "green"; duration: 100} NumberAnimation { id: animateOpacity target: flashingblob properties: "opacity" from: 0.99 to: 1.0 loops: Animation.Infinite easing {type: Easing.OutBack; overshoot: 500} } }
Specialized
property animation elements
have more efficient implementations than the
PropertyAnimation
element. They are for setting animations to different QML types such as
int
,
color
, and rotations. Similarly, the
ParentAnimation
can animate parent changes.
见 Controlling Animations section for more information about the different animation properties.
状态 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
Transition
element can contain
animation elements
to interpolate property changes caused by state changes. To assign the transition to an object, bind it to the
过渡
特性。
A button might have two states, the
pressed
state when the user clicks on the button and a
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
pressed
state to the
released
state. Likewise, there would be an animation during the change from the
released
state to the
pressed
状态。
Rectangle { width: 75; height: 75 id: button state: "RELEASED" MouseArea { anchors.fill: parent onPressed: button.state = "PRESSED" onReleased: button.state = "RELEASED" } states: [ State { name: "PRESSED" PropertyChanges { target: button; color: "lightblue"} }, State { name: "RELEASED" PropertyChanges { target: button; color: "lightsteelblue"} } ] transitions: [ Transition { from: "PRESSED" to: "RELEASED" ColorAnimation { target: button; duration: 100} }, Transition { from: "RELEASED" to: "PRESSED" ColorAnimation { target: button; duration: 100} } ] }
Binding the
to
and
from
properties to the state's name will assign that particular transition to the state change. For simple or symmetric transitions, setting the to
to
property to the wild card symbol, "
*
", denotes that the transition applies to any state change.
transitions:
Transition {
to: "*"
ColorAnimation { target: button; duration: 100}
}
Default property animations are set using
behavior animations
. Animations declared in
Behavior
elements apply to the property and animates any property value changes. However, Behavior elements have an
被启用
property to purposely enable or disable the behavior animations.
A ball component might have a behavior animation assigned to its
x
,
y
，和
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.
Rectangle { width: 75; height: 75; radius: width id: ball color: "salmon" Behavior on x { NumberAnimation { id: bouncebehavior easing { type: Easing.OutElastic amplitude: 1.0 period: 0.5 } } } Behavior on y { animation: bouncebehavior } Behavior { ColorAnimation { target: ball; duration: 100 } } }
There are several methods of assigning behavior animations to properties. The
Behavior on <property>
declaration is a convenient way of assigning a behavior animation onto a property.
见 Behaviors example for a demonstration of behavioral animations.
Animations can run in parallel or 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 SequentialAnimation and 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
opacity
property could transform to
1.0
denoting an opaque object. Using the
SequentialAnimation
element, the opacity animations will play after the preceding animation finishes. The
ParallelAnimation
element will play the animations at the same time.
Rectangle { id: banner width: 150; height: 100; border.color: "black" Column { anchors.centerIn: parent Text { id: code text: "Code less." opacity: 0.01 } Text { id: create text: "Create more." opacity: 0.01 } Text { id: deploy text: "Deploy everywhere." opacity: 0.01 } } MouseArea { anchors.fill: parent onPressed: playbanner.start() } SequentialAnimation { id: playbanner running: false NumberAnimation { target: code; property: "opacity"; to: 1.0; duration: 200} NumberAnimation { target: create; property: "opacity"; to: 1.0; duration: 200} NumberAnimation { target: deploy; property: "opacity"; to: 1.0; duration: 200} } }
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 SequentialAnimation element is also useful for playing transition animations because animations are played in parallel inside transitions.
See the Animation basics example for a demonstration of creating and combining multiple animations in QML.
There are different methods to control animations.
所有
animation elements
inherit from the
Animation
element. It is not possible to create
Animation
objects; instead, this element provides the essential properties and methods for animation elements. Animation elements have
start()
,
stop()
,
resume()
,
pause()
,
restart()
，和
complete()
-- all of these methods control the execution of animations.
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 easing 文档编制。
The easing example visually demonstrates each of the different easing types.
In addition, QML provides several other elements useful for animation:
These are specialized animation elements that animate different property types