One or more DoubleKeyFrame object elements that define the key frames for the animation. These can be any combination of LinearDoubleKeyFrame DiscreteDoubleKeyFrame, and SplineDoubleKeyFrame object elements. Object elements defined here become members of the KeyFrames collection when scripting accesses the KeyFrames property at runtime.
A key frame animation's target values are defined by its KeyFrames property, which contains a collection of DoubleKeyFrame objects. Each DoubleKeyFrame defines a segment of the animation with its own target Value and KeyTime properties. When the animation runs, it progresses from one key value to the next at the specified key times.
There are three types of DoubleKeyFrame classes, one for each supported interpolation method: LinearDoubleKeyFrame, DiscreteDoubleKeyFrame, and SplineDoubleKeyFrame.
When you declare a DoubleAnimationUsingKeyFrames in XAML, the order of the DoubleKeyFrame object elements is not significant, because the KeyTime property 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.
The following example moves a rectangle across a screen. The example uses a DoubleAnimationUsingKeyFrames object to animate the X property of a TranslateTransform object applied to a Rectangle object. This animation, which repeats indefinitely, uses three key frames in the following manner:
During the first three seconds, a LinearDoubleKeyFrame object moves the rectangle along a path at a steady rate from its starting position to the 500 position. Linear key frames, such as LinearDoubleKeyFrame, create a smooth linear transition between values.
At the end of the fourth second, a DiscreteDoubleKeyFrame object suddenly moves the rectangle to the next position. Discrete key frames, such as DiscreteDoubleKeyFrame, create sudden jumps between values. In this example, the rectangle is at the starting position and then suddenly appears at the 500 position.
In the final two seconds, a SplineDoubleKeyFrame object moves the rectangle back to its starting position. Spline key frames, such as SplineDoubleKeyFrame, create a variable transition between values according to the value of the KeySpline property. In this example, the rectangle begins by moving slowly and then speeds up exponentially toward the end of the time segment.
<Canvas xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Width="400" Height="300"> <Rectangle Fill="Blue" Width="50" Height="50"> <Rectangle.RenderTransform> <TranslateTransform x:Name="MyAnimatedTranslateTransform" X="0" Y="0" /> </Rectangle.RenderTransform> <Rectangle.Triggers> <EventTrigger RoutedEvent="Rectangle.Loaded"> <BeginStoryboard> <Storyboard> <!-- Animate the TranslateTransform X property from 0 to 350, then 50, then 200 over 10 seconds. --> <DoubleAnimationUsingKeyFrames Storyboard.TargetName="MyAnimatedTranslateTransform" Storyboard.TargetProperty="X" Duration="0:0:10"> <!-- Using a LinearDoubleKeyFrame, the rectangle moves steadily from its starting position to 500 over the first 3 seconds. --> <LinearDoubleKeyFrame Value="500" KeyTime="0:0:3" /> <!-- Using a DiscreteDoubleKeyFrame, the rectangle suddenly appears at 400 after the fourth second of the animation. --> <DiscreteDoubleKeyFrame Value="400" KeyTime="0:0:4" /> <!-- Using a SplineDoubleKeyFrame, the rectangle moves back to its starting point. The animation starts out slowly at first and then speeds up. This KeyFrame ends after the sixth second. --> <SplineDoubleKeyFrame KeySpline="0.6,0.0 0.9,0.00" Value="0" KeyTime="0:0:6" /> </DoubleAnimationUsingKeyFrames> </Storyboard> </BeginStoryboard> </EventTrigger> </Rectangle.Triggers> </Rectangle> </Canvas>