How to implement slurp effect on iPhone?

Question

The iPhone has a private list of effects that Apple uses, such as "genieEffect" and "slurpEffect". I'm wondering how one would go about implementing the slurp effect (this is when you trash a mail message or a note).

I understand how to use Core Animation, but I'm not sure exactly what parts of it they're using to get that animation.

Answer 1

This post talks about using the private API for the effect: link text

Answer 2

It seems to be a complex combination of 2D and 3D transformations. :-\ You'd have to really delve into CoreAnimation to simulate this effect.

Answer 3

I would do it with an affine transformation applied to the view's layer. Linear algebra is not my strong point ;) so I can't specify the exact transformation but my guess would be something like this for the animation:

• Set the alpha to fade to 0.0 or something close to 0
• Apply a transform to squish the two bottom corners close to the center
• Scale down the view to very small
• move the layer's center down to the bottom of the screen (or wherever you want it to genie to.

That's more or less how I think it would work. You might have to animate these things at different times, or all in one block, I'm not quite sure.

Have a look at documentation for CALayer, CABasicAnimation, and CGAffineTransform.