發行項
11/17/2011

PointAnimationUsingKeyFrames Class

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Animates the value of a Point property along a set of KeyFrames.

Inheritance Hierarchy

System.Object
  System.Windows.DependencyObject
    System.Windows.Media.Animation.Timeline
      System.Windows.Media.Animation.PointAnimationUsingKeyFrames

Namespace: System.Windows.Media.Animation
Assembly: System.Windows (in System.Windows.dll)

Syntax

'Declaration
<ContentPropertyAttribute("KeyFrames", True)> _
Public NotInheritable Class PointAnimationUsingKeyFrames _
    Inherits Timeline

[ContentPropertyAttribute("KeyFrames", true)]
public sealed class PointAnimationUsingKeyFrames : Timeline

<PointAnimationUsingKeyFrames>
  oneOrMorePointKeyFrames
</PointAnimationUsingKeyFrames>

XAML Values

oneOrMorePointKeyFrames
One or more object elements that define the key frames for the animation. These object elements represent one of the classes deriving from PointKeyFrame. These are typically any combination of LinearPointKeyFrame, EasingPointKeyFrame, DiscretePointKeyFrame, and SplinePointKeyFrame. Object elements defined here become members of the PointKeyFrameCollection collection when code accesses the KeyFrames property at run time.

The PointAnimationUsingKeyFrames type exposes the following members.

Constructors

	Name	Description
	PointAnimationUsingKeyFrames	Initializes a new instance of the PointAnimationUsingKeyFrames class.

Top

Properties

	Name	Description
	AutoReverse	Gets or sets a value that indicates whether the timeline plays in reverse after it completes a forward iteration. (Inherited from Timeline.)
	BeginTime	Gets or sets the time at which this Timeline should begin. (Inherited from Timeline.)
	Dispatcher	Gets the Dispatcher this object is associated with. (Inherited from DependencyObject.)
	Duration	Gets or sets the length of time for which this timeline plays, not counting repetitions. (Inherited from Timeline.)
	FillBehavior	Gets or sets a value that specifies how the animation behaves after it reaches the end of its active period. (Inherited from Timeline.)
	KeyFrames	Gets the collection of PointKeyFrame objects that define the animation.
	RepeatBehavior	Gets or sets the repeating behavior of this timeline. (Inherited from Timeline.)
	SpeedRatio	Gets or sets the rate, relative to its parent, at which time progresses for this Timeline. (Inherited from Timeline.)

Top

Methods

	Name	Description
	CheckAccess	Determines whether the calling thread has access to this object. (Inherited from DependencyObject.)
	ClearValue	Clears the local value of a dependency property. (Inherited from DependencyObject.)
	Equals(Object)	Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	GetAnimationBaseValue	Returns any base value established for a Silverlight dependency property, which would apply in cases where an animation is not active. (Inherited from DependencyObject.)
	GetHashCode	Serves as a hash function for a particular type. (Inherited from Object.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	GetValue	Returns the current effective value of a dependency property from a DependencyObject. (Inherited from DependencyObject.)
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	ReadLocalValue	Returns the local value of a dependency property, if a local value is set. (Inherited from DependencyObject.)
	SetValue	Sets the local value of a dependency property on a DependencyObject. (Inherited from DependencyObject.)
	ToString	Returns a string that represents the current object. (Inherited from Object.)

Top

Events

	Name	Description
	Completed	Occurs when the Storyboard object has completed playing. (Inherited from Timeline.)

Top

Remarks

A key frame animation's target values are defined by its KeyFrames property, which contains a collection of PointKeyFrame objects. Each PointKeyFrame defines a segment of the animation with its own target Value and KeyTime. When the animation runs, it progresses from one key value to the next at the specified key times.

There are several types of PointKeyFrame classes, one for each supported interpolation method: LinearPointKeyFrame, EasingPointKeyFrame, DiscretePointKeyFrame, and SplinePointKeyFrame.

Unlike a PointAnimation, a PointAnimationUsingKeyFrames can have more than two target values. You can also control the interpolation method of individual PointKeyFrame segments.

When declaring a PointAnimationUsingKeyFrames in XAML, the order of the PointKeyFrame object elements is not significant, because the KeyTime controls the timing and therefore the order in which the key frames are executed. However, it is good markup style to keep the element order the same as the KeyTime sequence order.

Examples

The following example moves an ellipse along a triangular path. The example uses the PointAnimationUsingKeyFrames class to animate the Center property of an EllipseGeometry. This animation uses three key frames in the following manner:

During the first half second, it uses an instance of the LinearPointKeyFrame class to move the ellipse along a path at a steady rate from its starting position. Linear key frames such as LinearPointKeyFrame create a smooth linear interpolation between values.
During the end of the next half second, it uses an instance of the DiscretePointKeyFrame class to suddenly move the ellipse along the path to the next position. Discrete key frames like DiscretePointKeyFrame create sudden jumps between values.
During the final two seconds, it uses an instance of the SplinePointKeyFrame class to move the ellipse back to its starting position. Spline key frames like SplinePointKeyFrame create a variable transition between values according to the values of the KeySpline property. In this example, the animation begins slowly and speeds up exponentially toward the end of the time segment.

Run this sample

<Canvas Width="400" Height="300">
    <Canvas.Resources>
        <Storyboard x:Name="myStoryboard">

            <!-- Animating the Center property uses 3 KeyFrames, which animate
             the ellipse allong a triangular path. -->
            <PointAnimationUsingKeyFrames
          Storyboard.TargetProperty="Center"
          Storyboard.TargetName="MyAnimatedEllipseGeometry"
          Duration="0:0:5" RepeatBehavior="Forever">

                <!-- Over the first half second, Using a LinearPointKeyFrame, the ellipse 
               moves steadily from its starting position along the first line of the 
               trianglar path.  -->
                <LinearPointKeyFrame KeyTime="0:0:0.5" Value="100,300" />

                <!-- Using a DiscretePointKeyFrame, the ellipse suddenly changes position
               after the first second of the animation. -->
                <DiscretePointKeyFrame KeyTime="0:0:1" Value="400,300" />

                <!-- Using a SplinePointKeyFrame, the ellipse moves back to its starting
               position. It moves slowly at first and then speeds up. This key frame 
               takes 2 seconds to complete. -->
                <SplinePointKeyFrame KeySpline="0.6,0.0 0.9,0.00" 
                 KeyTime="0:0:3" Value="200,100" />
            </PointAnimationUsingKeyFrames>
        </Storyboard>
    </Canvas.Resources>
    <Path Fill="Blue" Loaded="Start_Animation">
        <Path.Data>

            <!-- Describes an ellipse. -->
            <EllipseGeometry x:Name="MyAnimatedEllipseGeometry"
             Center="200,100" RadiusX="15" RadiusY="15" />
        </Path.Data>
    </Path>
</Canvas>

' Start the animation when the object loads
Private Sub Start_Animation(ByVal sender As Object, ByVal e As EventArgs)
    myStoryboard.Begin()
End Sub

// Start the animation when the object loads
private void Start_Animation(object sender, EventArgs e)
{
    myStoryboard.Begin();
}

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

共用方式為