项目
11/18/2011

PowerEase Class

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Represents an easing function that creates an animation that accelerates and/or decelerates using the formula f(t) = tp where p is equal to the Power property.

Inheritance Hierarchy

System.Object
  System.Windows.DependencyObject
    System.Windows.Media.Animation.EasingFunctionBase
      System.Windows.Media.Animation.PowerEase

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

Syntax

'Declaration
Public Class PowerEase _
    Inherits EasingFunctionBase

public class PowerEase : EasingFunctionBase

<PowerEase .../>

The PowerEase type exposes the following members.

Constructors

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

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Properties

	Name	Description
	Dispatcher	Gets the Dispatcher this object is associated with. (Inherited from DependencyObject.)
	EasingMode	Gets or sets a value that specifies how the animation interpolates. (Inherited from EasingFunctionBase.)
	Power	Gets or sets the exponential power of the animation interpolation. For example, a value of 7 creates an animation interpolation curve that follows the formula f(t) = t7.

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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.)
	Ease	Transforms normalized time to control the pace of an animation. (Inherited from EasingFunctionBase.)
	EaseInCore	Provides the logic portion of the easing function that you can override to produce the EaseIn mode of the custom easing function. (Overrides EasingFunctionBase.EaseInCore(Double).)
	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.)

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Fields

	Name	Description
	PowerProperty	Identifies the Power dependency property.

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Remarks

You can control whether the animation accelerates, decelerates, or both by specifying the EasingMode. The following graph demonstrates the different values of EasingMode, where f(t) represents the animation progress and t represents time.

CubicEase EasingMode graphs.

By using the PowerEase function, you can specify how quickly acceleration/deceleration takes place by specifying the Power property:

f(t) = tp where p is equal to the Power property.

Because of this, the PowerEase function can be substituted for QuadraticEase (f(t) = t2), CubicEase (f(t) = t3), QuarticEase (f(t) = t4), and QuinticEase (f(t) = t5). For example, if you wanted to use a PowerEase function to create the same behavior as a QuadraticEase function (f(t) = t2), you would specify a Power property value of 2.

There are several other easing functions besides PowerEase which you can explore using the following sample.

Run this sample

In addition to using the easing functions included in the run-time, you can create your own custom easing functions by inheriting from EasingFunctionBase.

Examples

The following example applies a PowerEase easing function with a Power property value of 20 to a DoubleAnimation to create a decelerating animation. Because the Power value is so high, the deceleration is sudden compared to if you used a lower value.

Run this sample

<StackPanel x:Name="LayoutRoot" Background="White">
    <StackPanel.Resources>
        <Storyboard x:Name="myStoryboard">
            <DoubleAnimation From="30" To="200" Duration="00:00:3" 
                Storyboard.TargetName="myRectangle" 
                Storyboard.TargetProperty="Height">
                <DoubleAnimation.EasingFunction>
                    <PowerEase Power="20" EasingMode="EaseOut"/>
                </DoubleAnimation.EasingFunction>
            </DoubleAnimation>
        </Storyboard>
    </StackPanel.Resources>

    <Rectangle x:Name="myRectangle" MouseLeftButtonDown="Mouse_Clicked" 
     Fill="Blue" Width="200" Height="30" />

</StackPanel>

' When the user clicks the rectangle, the animation
' begins. 
Private Sub Mouse_Clicked(ByVal sender As Object, ByVal e As MouseEventArgs)
    myStoryboard.Begin()
End Sub

// When the user clicks the rectangle, the animation
// begins. 
private void Mouse_Clicked(object sender, MouseEventArgs 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.

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