iPhone “slide to unlock” animation

Question

Any ideas as to how Apple implemented the \"slide to unlock\" (also, \"slide to power off\" is another identical example) animation?

I thought about some sort of ani

Answer 1

Thanks to rpetrich for the clipping gradient recipe. I am a newbie iPhone and Cocoa developer, so I was real happy to find it.

I've implemented a decent-looking Slide to Cancel UIViewController using rpetrich's method. You can download the Xcode project of my implementation from here.

My implementation uses a repeating NSTimer. I was unable to figure out how use Core (or Gore) Animation to have the iPhone's graphics engine continuously move the highlighting. I think that could be done on OS X with CALayer mask layers, but mask layers are not supported on iPhone OS.

When I play with Apple's "Slide to Unlock" slider on my iPhone's home screen, I occasionally see the animation freeze. So I think Apple may be using a timer as well.

If anyone can figure out how to do a non-timer based implementation using CA or OpenGL, I would love to see it.

Thanks for the help!