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LinearPointKeyFrame Class

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

Animates from the Point value of the previous key frame to its own Value using linear interpolation.

Inheritance Hierarchy

System.Object
  System.Windows.DependencyObject
    System.Windows.Media.Animation.PointKeyFrame
      System.Windows.Media.Animation.LinearPointKeyFrame

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

Syntax

'Declaration
Public NotInheritable Class LinearPointKeyFrame _
    Inherits PointKeyFrame

public sealed class LinearPointKeyFrame : PointKeyFrame

<LinearPointKeyFrame .../>

The LinearPointKeyFrame type exposes the following members.

Constructors

  Name Description
Public methodSupported by Silverlight for Windows Phone LinearPointKeyFrame Initializes a new instance of the LinearPointKeyFrame class.

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Properties

  Name Description
Public propertySupported by Silverlight for Windows Phone Dispatcher Gets the Dispatcher this object is associated with. (Inherited from DependencyObject.)
Public propertySupported by Silverlight for Windows Phone KeyTime Gets or sets the time at which the key frame's target Value should be reached. (Inherited from PointKeyFrame.)
Public propertySupported by Silverlight for Windows Phone Value Gets or sets the key frame's target value. (Inherited from PointKeyFrame.)

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Methods

  Name Description
Public methodSupported by Silverlight for Windows Phone CheckAccess Determines whether the calling thread has access to this object. (Inherited from DependencyObject.)
Public methodSupported by Silverlight for Windows Phone ClearValue Clears the local value of a dependency property. (Inherited from DependencyObject.)
Public methodSupported by Silverlight for Windows Phone Equals(Object) Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected methodSupported by Silverlight for Windows Phone 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.)
Public methodSupported by Silverlight for Windows Phone 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.)
Public methodSupported by Silverlight for Windows Phone GetHashCode Serves as a hash function for a particular type. (Inherited from Object.)
Public methodSupported by Silverlight for Windows Phone GetType Gets the Type of the current instance. (Inherited from Object.)
Public methodSupported by Silverlight for Windows Phone GetValue Returns the current effective value of a dependency property from a DependencyObject. (Inherited from DependencyObject.)
Protected methodSupported by Silverlight for Windows Phone MemberwiseClone Creates a shallow copy of the current Object. (Inherited from Object.)
Public methodSupported by Silverlight for Windows Phone ReadLocalValue Returns the local value of a dependency property, if a local value is set. (Inherited from DependencyObject.)
Public methodSupported by Silverlight for Windows Phone SetValue Sets the local value of a dependency property on a DependencyObject. (Inherited from DependencyObject.)
Public methodSupported by Silverlight for Windows Phone ToString Returns a string that represents the current object. (Inherited from Object.)

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Remarks

This class is used as part of a PointKeyFrameCollection in conjunction with a PointAnimationUsingKeyFrames to animate a Point property value along a set of key frames.

A key frame defines a segment of the PointAnimationUsingKeyFrames to which it belongs. Each key frame has a target Value and a KeyTime. The KeyTime specifies the time at which the key frame's Value should be reached. A key frame animates from the target value of the previous key frame to its own target value. It starts when the previous key frame ends and ends when its own key time is reached.

Linear key frames like LinearPointKeyFrame create a smooth, linear interpolation between values.

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:

  1. 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.

  2. 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.

  3. 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.