Friday, March 12, 2010

Video: Creating a Reusable Animation Library

Creating a Reusable Flash Animation Library, the next episode in the gripping and suspenseful series CodeDependent, is now available from Adobe TV.

This episode is a bit of a departure from my normal shows. Usually, I show graphics and animation techniques in Flex and Flex 4. This time, I talk about Flash Pro, the authoring tool for Flash (not Flex) applications. In particular, I show how to create a reusable library in Flash Pro that you can then link to and use in other Flash Pro projects. The process of creating a library in Flash Pro wasn't obvious to me, so I thought it might be useful to show how it was done. Thanks to Trevor McCauley for helping me figure this out. Trevor's on the Flash player team and is very helpful is figuring out all kinds of things about how Flash works, including this bit about Flash authoring. Check out his blog at

Here's how this relates to Flex and my work for Flex: the library I create is an animation library based on the core facilities underlying the Flex effects. I call the library Flexy.

Flex effects are pretty dependent on the Flex library overall. They use concepts in UIComponent, graphic elements, styles, and other concepts that are found in the core Flex framework. So building a full-on Flex effects library in Flash Pro would necessarily drag in so much of the Flex infrastructure that it wouldn't be worth the effort; you might as well just use Flex directly.

But the underlying animation engine that the new Flex 4 effects depend on, including the Animation class, arbitrary type interpolation, and the new easer interface and classes, are independent of Flex effects and of nearly everything else in Flex. I wanted to see if I could break those animation facilities out into a separable library. There were various niggling dependencies, such as the use of the EffectEvent class, some use of resource bundles for error strings, and other minor issues, but one 50-minute train commute later, I had a 13k library built in Flash Pro that had no Flex dependencies and had all of the underlying animation support that the Flex effects use for running their animations.

Flexy doesn't handle all of the effects functionality, of course, because Flex effects aren't part of the port. Flex effects provide mainly two extra layers of support for animations. First, they handle setting animated values on target objects/properties. The animation infrastructure only handles calculating the animated values, not what to do with those values. Second, effects have extra built-in logic and convenience APIs that makes it easier to declare and run effects than you might otherwise have to do with a more manual approach to animation.

I can't do much about the second bit; that's most of the code in effects, and I was looking for something simple. But for the first part, I've provided a utility class called PropertyAnimator which you can use to automate assigning animated values to properties, just like effects do. It simplifies using Animation and makes very easy property animation possible with this library.

Check out Flexy and see what you can do with it. And come back for the next show to see a simple example of using the library from within Flash Pro.

Here's the video:

There is no demo application this time, because the demo is really just the reusable Flexy library, which isn't very exciting to watch, as demos go, because it just sits there, being reusable.

Here is the demo code. This is a zip file containing the Flash Pro project (Flexy.fla), the Flexy library itself (Flexy.swc), and the source code that Flexy was built with.

Users of the Flex Animation class should be able to start playing with the library pretty easily, but if the API is a bit of a mystery to you, check back for my next show, in which I'll dmeonstrate how to use the library in Flash Pro for a simple example.

Here's where you can find CodeDependent on iTunes.

And here's where you can find CodeDependent on YouTube.



Christian Giordano said...

Definitely interested to see where this is going. Thanks, chr

Tink said...

Hi Chet

Can I ask why you chose to do this in the Flash IDE?

Whats the advantage here over using FB?

Chet Haase said...

@Tink: good question; this obviously could have been done in Flash Builder, which is where I spend most of my life. There were basically 2 reasons I did it in Flash Pro:
1) The "nothing's up my sleeve" equivalent for building a Flex-less library. I wanted to make sure, and make clear, that the library was completely separate from Flex and didn't drag in any hidden framework files. Building the project in Flash Pro, which doesn't have access to any Flex framework files, was a good way to make sure.
2) I do use Flash Pro occasionally, mostly for reproducing bugs for the player team, and I look for opportunities to learn more about it. This was one.
Also, the follow-up show shows how I then use the library in a Flash project. So it made sense to both produce and consume the library in that tool.

Tink said...

Right, I get you, more for examples sake.

Thought it might be worth mentioning that creating library projects in FB is a much quicker way to create SWC's that can be used without the Flex framework (due to its superior code editor, and you don't have to publish to update your SWC).

It's not too difficult to use parts of the Flex framework in Flash Pro (things like collectrions, bindings). Just link in the SWC's and your off an running.

That said I think Flash Pro is much more suited to create graphic assets an annimations which then get used in an FB project (whether Flex or straight AS 3.0).