BackEase Class

BackEase Class

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

Represents an easing function that retracts the motion of an animation slightly before it begins to animate in the path indicated.

Namespace:  System.Windows.Media.Animation
Assembly:  System.Windows (in System.Windows.dll)
XMLNS for XAML: Not mapped to an xmlns.

public class BackEase : EasingFunctionBase

The BackEase type exposes the following members.

  NameDescription
Public methodBackEaseInitializes a new instance of the BackEase class.
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  NameDescription
Public propertyAmplitudeGets or sets the amplitude of retraction associated with a BackEase animation.
Public propertyDispatcherGets the Dispatcher this object is associated with. (Inherited from DependencyObject.)
Public propertyEasingModeGets or sets a value that specifies how the animation interpolates. (Inherited from EasingFunctionBase.)
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  NameDescription
Public methodCheckAccessDetermines whether the calling thread has access to this object. (Inherited from DependencyObject.)
Public methodClearValueClears the local value of a dependency property. (Inherited from DependencyObject.)
Public methodEaseTransforms normalized time to control the pace of an animation. (Inherited from EasingFunctionBase.)
Protected methodEaseInCoreProvides 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).)
Public methodEquals(Object)Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
Public methodGetAnimationBaseValueReturns any base value established for a Windows Phone dependency property, which would apply in cases where an animation is not active. (Inherited from DependencyObject.)
Public methodGetHashCodeServes as a hash function for a particular type. (Inherited from Object.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodGetValueReturns the current effective value of a dependency property from a DependencyObject. (Inherited from DependencyObject.)
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodReadLocalValueReturns the local value of a dependency property, if a local value is set. (Inherited from DependencyObject.)
Public methodSetValueSets the local value of a dependency property on a DependencyObject. (Inherited from DependencyObject.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
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  NameDescription
Public fieldStatic memberAmplitudePropertyIdentifies the Amplitude dependency property.
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You can control when the "back up" behavior occurs in an animation by specifying the EasingMode property value on an animation. The following graph demonstrate the different values of EasingMode, where f(t) represents the animation progress and t represents time.

BackEase EasingMode graphs.

The formula used for this function is the following.

BackEase formula.
NoteNote:

Because this animation causes values to retract before progressing, the animation might interpolate into negative numbers unexpectedly. This can cause errors when animating properties that do not allow negative numbers. For example, if you apply this animation to the Height of an object (e.g. from 0 to 200 with an EasingMode of EaseIn), the animation will attempt to interpolate through negative numbers for Height which will throw an error.

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

The following example applies a BackEase easing function to a DoubleAnimation to create an animation that retracts slightly at the beginning and end of the animation.


<StackPanel x:Name="LayoutRoot" Background="Transparent">
    <StackPanel.Resources>
        <Storyboard x:Name="myStoryboard">
            <DoubleAnimation From="1" To="2" Duration="00:00:1" 
                Storyboard.TargetName="myScaleTransform" 
                Storyboard.TargetProperty="ScaleX">
                <DoubleAnimation.EasingFunction>
                    <BackEase Amplitude="0.3" EasingMode="EaseInOut" />
                </DoubleAnimation.EasingFunction>
            </DoubleAnimation>
            <DoubleAnimation From="1" To="2" Duration="00:00:1" 
                Storyboard.TargetName="myScaleTransform" 
                Storyboard.TargetProperty="ScaleY">
                <DoubleAnimation.EasingFunction>
                    <BackEase Amplitude="0.3" EasingMode="EaseInOut" />
                </DoubleAnimation.EasingFunction>
            </DoubleAnimation>
        </Storyboard>
    </StackPanel.Resources>

    <Rectangle Margin="60" x:Name="myRectangle" MouseLeftButtonDown="Mouse_Clicked" 
     Fill="Blue" Width="50" Height="50" >

        <Rectangle.RenderTransform>
            <ScaleTransform x:Name="myScaleTransform" />
        </Rectangle.RenderTransform>

    </Rectangle>
</StackPanel>



// When the user clicks the rectangle, the animation
// begins. 
private void Mouse_Clicked(object sender, MouseEventArgs e)
{
    myStoryboard.Begin();
}


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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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