Monday, October 26, 2009

Video: Custom Type Interpolation in Flex 4 Effects

Custom Type Interpolation in Flex 4 Effects, the next episode in the gripping and suspenseful series CodeDependent, is now available from Adobe TV.

In this show, we see an introduction to the new system of type interpolation in Flex 4 effects. The ability to animate properties of arbitrary type is one of the key new features in the Flex 4 effects system. Previously, in Flex 3, the effects system dealt only with numbers. It was great at animating any properties of components at all ... as long as those properties were numeric. In particular, it knew how to calculate a numeric value during animations, given start and end values. Calculating these values is important, of course, because animations are specified with start and end values only (or, in the case of the new keyframes in Flex 4 effects, a series of intermediate values), and any other value that the property takes on during the animation must be calculated as a product of these start/end values plus the elapsed fraction of the animation.

Flex's ability to deal with only numbers was fine for most of the cases that UI developers would care about because, frankly, most of the properties on components are numbers: x position, y position, width, height, alpha, scaleX, scaleY - all of these are simple Numbers that can easily be tossed into a simple parameteric function to calculate an in-between number for Flex 3 animations.

But what if you want to animate a property that is not a number, like a Rectangle, or a Point, or some object specific to your code that we know nothing about? Or what if it is a number, but you can't calculate a simple interpolation of it numerically (like RGB colors, which we talked about in an earlier episode)? In that case, we need a way to calculate the in-between values for objects of that type. The new IInterpolator interface in Flex 4 exists for that purpose: you can create implementations of that interface and supply them to Flex 4 effects to tell us how to interpolate in-between values for these types and the effects can take it from there, calling your interpolators whenever they need to calculate animated values for properties of those types..

This video shows how we can write a custom interpolator for an arbitrary data structure (in this case, a Rectangle) and supply it to a Flex 4 Animate effect to have it animate our object.

Here's the video:

Here is the demo application:

And here is the source code.

Finally, here's where you can find the CodeDependent videos on iTunes.


1 comment:

polyGeek said...

I really appreciate you using simple examples. All to often people get carried away and pile in unnecessary code that distracts from the topic at hand. You just give us the basics and let us interpolate from there.