Time for a brief but fun post... some time back Tim Heuer posted the Silverlight 3 bouncing plane gratuitous demo. Click an element, and the nearest corner would bounce backwards and forwards as it comes back to rest.
Tim had the code to setup the storyboards, and handle the mouse interaction in code-behind. I look at it, and immediately see a reusable component (even if it is a gratuitous one), or more specifically a behavior, that encapsulates all the logic, and can be attached declaratively in XAML to one or more elements simply without needing any code-behind logic. So I created one such behavior. I used this behavior in my TwitterBug sample at TechEd recently, and thought it could use a dedicated blog post. :-)
Here is a screenshot, which really doesn’t do much justice to something interactive. So go ahead, and click it to run the sample live. Click around on the images. And if you’re wondering how its done, go ahead and download the code. You’ll see a BouncingPlane class that derives from Behavior.
Here is a an example of using the behavior in XAML as applied to one of the images in the application:
<Border Grid.Column="2" Grid.Row="0" Style="{StaticResource borderStyle}">
<fxui:Interaction.Behaviors>
<demo:BouncingPlane />
</fxui:Interaction.Behaviors>
<Image Style="{StaticResource imageStyle}" Source="/Images/Penguins.jpg" />
</Border>
There isn’t anything really new in the specifics of the implementation - I just refactored the code-behind logic into a behavior, but it does show the power of the behavior concept. Here is the sample code for you to download and check out.
I've been quite fond of the behavior concept for a long while now. I first did an implementation of the behaviors concept in asp.net ajax as well as control extender server controls on the server, and then in Silverlight.FX. More recently, I worked with the Blend team on getting this concept into Expression where they’re really becoming popular. I hope they will be in the SDK proper at some point in the future.
I think behaviors are truly useful (and essential) in UI and in declarative programming as a lightweight component mechanism that is based on composition rather than derivation.
Posted on Thursday, 8/27/2009 @ 4:15 PM
| #
Silverlight