项目
11/18/2011

DiscreteObjectKeyFrame Class

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Animates from the Object value of the previous key frame to its own Value using discrete values.

Inheritance Hierarchy

System.Object
  System.Windows.DependencyObject
    System.Windows.Media.Animation.ObjectKeyFrame
      System.Windows.Media.Animation.DiscreteObjectKeyFrame

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

Syntax

'Declaration
Public NotInheritable Class DiscreteObjectKeyFrame _
    Inherits ObjectKeyFrame

public sealed class DiscreteObjectKeyFrame : ObjectKeyFrame

<DiscreteObjectKeyFrame ...>
  <DiscreteObjectKeyFrame.Value>
    objectValue
  </DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame ...>
-or-
</DiscreteObjectKeyFrame Value="objectAsAttribute"...>

XAML Values

objectValue
An object element that declares the value of the object to use for the key frame.
objectAsAttribute
A string attribute value that can be converted to an object value.

The DiscreteObjectKeyFrame type exposes the following members.

Constructors

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

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Properties

	Name	Description
	Dispatcher	Gets the Dispatcher this object is associated with. (Inherited from DependencyObject.)
	KeyTime	Gets or sets the time at which the key frame's target Value should be reached. (Inherited from ObjectKeyFrame.)
	Value	Gets or sets the key frame's target value. (Inherited from ObjectKeyFrame.)

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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.)
	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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Remarks

This class is used as part of a ObjectKeyFrameCollection in conjunction with a ObjectAnimationUsingKeyFrames to animate an Object property value along a set of key frames.

A key frame defines a segment of the ObjectAnimationUsingKeyFrames 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.

Discrete key frames like DiscreteObjectKeyFrame create sudden "jumps" between values (no interpolation). In other words, the animated property does not change until the key frame's key time is reached, at which point the animated property goes suddenly to the target value.

The XAML usage shown is the one most likely to be used for real DiscreteObjectKeyFrame scenarios. Value is a property inherited from the ObjectKeyFrame base class, and for other key frame types (like PointKeyFrame) Value is typically given as an attribute. But DiscreteObjectKeyFrame is specifically meant for objects, which sometimes cannot be expressed in attribute form.

Objects that can be expressed in attribute form include any object that has a native conversion behavior. This includes language primitives, or enumeration values. Other objects may require the property element form in order to be specified as a Value.

One particular scenario for DiscreteObjectKeyFrame is for providing visual state property values for controls, when the control properties take enumerated values or values of common primitives such as Int32, Boolean, or String. For more information, see Creating a New Control by Creating a ControlTemplate.

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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