Animation and Transitions Types
Transition - Animates transitions during state changes 狀態變化時的動畫過渡
SequentialAnimation - Runs animations sequentially 序列播放動畫
ParallelAnimation - Runs animations in parallel 平行播放動畫
Behavior - Specifies a default animation for property changes 指定屬性改變時的默認動畫
PropertyAction - Sets immediate property changes during animation 動畫過程中立即設置屬性
PauseAnimation - Introduces a pause in an animation 暫停動畫
SmoothedAnimation - Allows a property to smoothly track a value 平滑的動畫
SpringAnimation - Allows a property to track a value in a spring-like motion 彈簧動畫
ScriptAction - Runs scripts during an animation 允許允許Javascript 在動畫中
Types that animate properties based on data types
AnchorAnimation
Animates changes in anchor values
ColorAnimation
Animates changes in color values
NumberAnimation
Animates changes in qreal-type values
ParentAnimation
Animates changes in parent values
PathAnimation
Animates an item along a path
PropertyAnimation
Animates changes in property values
RotationAnimation
Animates changes in rotation values
Vector3dAnimation
Animates changes in QVector3d values
Animations are created by applying animation types to property values. Animation types will interpolate property values to create smooth transitions. As well, state transitions may assign 分配 animations to state changes.
To create an animation, use an appropriate animation type for the type of the property that is to be animated, and apply the animation depending on the type of behavior that is required.
Triggering Animations 觸發動畫
There are several ways of setting animation to an object.
Direct Property Animation
Animations are created by applying animation objects to property values to gradually change the properties over time. These property animations apply smooth movements by interpolating values between property value changes. Property animations provide timing controls and allows different interpolations 插入 through easing curves.
Rectangle {
id: flashingblob
width: 75; height: 75
color: “blue”
opacity: 1.0
MouseArea {
anchors.fill: parent
onClicked: { 點擊鼠標時執行的動畫
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 循環 : Animation.Infinite 無限
easing {type: Easing.OutBack; overshoot: 500}
}
}
Specialized property animation types have more efficient implementations than the PropertyAnimation type. They are for setting animations to different QML types such as int, color, and rotations選擇. Similarly, the ParentAnimation can animate parent changes.
See the Controlling Animations section for more information about the different animation properties.
Using Predefined Targets and Properties
In the previous example, the PropertyAnimation and NumberAnimation objects needed to specify particular target and properties values to specify the objects and properties that should be animated. 需要指定特定 的目標和屬性 This can be avoided by using the on syntax, which specifies the animation is to be applied as a property value source.
Below are two PropertyAnimation objects that are specified using this syntax:
import QtQuick 2.0
Rectangle {
id: rect
width: 100; height: 100
color: “red”
PropertyAnimation on x { to: 100 } // 對比之前的語法 這種定義動畫的方式指定了 目標 和 屬性
PropertyAnimation on y { to: 100 } // 這種方法在圖形加載時就執行了，對PropertyAnimation沒有意義
}
The animation starts as soon as the rectangle is loaded, 動畫當圖形加載的時候啓動 and will automatically be applied to its x and y values. Since the on syntax has been used, it is not necessary to set the target value of the PropertyAnimation objects to rect, and neither is it necessary to set the property values to x and y.
This can also be used by grouped animations to ensure that all animations within a group are applied to the same property. For example, the previous example could instead use SequentialAnimation to animate the rectangle’s color first to yellow, then to blue:
import QtQuick 2.0
Rectangle {
width: 100; height: 100
color: “red”
SequentialAnimation on color { // Predined 方式 可以應用於 SequentialAnimation 指定每個動畫的時間
ColorAnimation { to: "yellow"; duration: 1000 }
ColorAnimation { to: "blue"; duration: 1000 }
}
}
Since the SequentialAnimation object has been specified on the color property using the on syntax, its child ColorAnimation objects are also automatically applied to this property and do not need to specify target or property animation values.
Transitions during State Changes
Qt Quick States are property configurations where a property may have different values to reflect different states. State changes introduce abrupt生硬 property changes; animations smooth transitions to produce visually appealing 吸引人的 state changes.
The Transition type can contain animation types to interpolate 插入 property changes caused by state changes. To assign the transition to an object, bind it to the transitions property.
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 state.
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 指定 that particular transition to the state change. For simple or symmetric 對稱的 transitions, setting the to to property to the wild card symbol, “*”, denotes 表示 that the transition applies to any state change.
transitions:
Transition {
to: “*” // 應用於任何狀態變化
ColorAnimation { target: button; duration: 100}
}
Default Animation as Behaviors 默認的動畫叫做行爲
Default property animations are set using behavior animations. Animations declared in Behavior types apply to the property and animates any property value changes. However, Behavior types have an enabled property to purposely enable or disable the behavior animations.
A ball component might have a behavior animation assigned to its x, y, and color properties. The behavior animation could be set up to simulate an elastic effect.模仿一個彈性效果 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 { //釋放
type: Easing.OutElastic
amplitude: 1.0 // 振幅
period: 0.5 //週期
}
}
}
Behavior on y {
animation: bouncebehavior
}
Behavior {
ColorAnimation { target: ball; duration: 100 }
}
}
There are several methods of assigning behavior animations to properties. The Behavior on declaration is a convenient way of assigning a behavior animation onto a property.
See the Qt Quick Examples - Animation for a demonstration 示範 of behavioral animations.
Playing Animations in Parallel or in Sequence
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 旗幟 component may have several icons or slogans 口號 to display, one after the other. The opacity property could transform to 1.0 denoting an opaque 不透明 object. Using the SequentialAnimation type, the opacity animations will play after the preceding animation finishes. The ParallelAnimation type 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() // 調用動畫
}
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 type is also useful for playing transition animations because animations are played in parallel inside transitions.
Controlling Animations 動畫控制
There are different methods to control animations.
Animation Playback 重放
All animation types inherit from the Animation type. It is not possible to create Animation objects; instead, this type provides the essential properties and methods for animation types. Animation types have start(), stop(), resume(), pause(), restart(), and complete() – all of these methods control the execution 執行 of animations.
Easing
Easing 釋放 curves 曲線 define how the animation will interpolate 插值 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, 彈跳 acceleration 加速, deceleration 減速, and cyclical 週期 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 獨有的 to a particular curve 特別的曲線. For more information about the easing curves, visit the easing documentation.
The easing example visually demonstrates each of the different easing types.
Other Animation Types
In addition, QML provides several other types useful for animation:
PauseAnimation: enables pauses during animations
ScriptAction: allows JavaScript to be executed during an animation, and can be used together with StateChangeScript to reused existing scripts
PropertyAction: changes a property immediately during an animation, without animating the property change
These are specialized animation types that animate different property types
SmoothedAnimation: a specialized NumberAnimation that provides smooth changes in animation when the target value changes
SpringAnimation: provides a spring-like animation with specialized attributes such as mass, damping and epsilon
ParentAnimation: used for animating a parent change (see ParentChange)
AnchorAnimation: used for animating an anchor change (see AnchorChanges)
Sharing Animation Instances
Sharing animation instances between Transitions or Behaviors is not supported, and may lead to undefined behavior. In the following example, changes to the Rectangle’s position will most likely not be correctly animated.
Rectangle {
// NOT SUPPORTED: this will not work correctly as both Behaviors
// try to control a single animation instance
NumberAnimation { id: anim; duration: 300; easing.type: Easing.InBack } // 動畫實例 行爲相同時可以被應用到不同對象
Behavior on x { animation: anim }
Behavior on y { animation: anim }
}
The easiest fix is to repeat the NumberAnimation for both Behaviors. If the repeated animation is rather complex, you might also consider creating a custom animation component and assigning an instance to each Behavior, for example:
//當動畫很複雜時，寫入一個獨立的文件
// MyNumberAnimation.qml
NumberAnimation { id: anim; duration: 300; easing.type: Easing.InBack }
// main.qml
Rectangle {
Behavior on x { MyNumberAnimation {} } // 寫在其他文件中的調用方法
Behavior on y { MyNumberAnimation {} }
}