Hey guys, I've just had a nagging question for a while regarding iPhone app user interfaces. For example, consider WeightBot's User Interface. I am wondering, how are most of these user interfaces created? In general, of course.

Is there a way to simply design controls (that is, the images) in a program like Photoshop, then use that 'skin' for controls in UIKit? I realize that there are some controls that are probably created by the programmer (custom controls), but I'm referring to the ready-made ones that come in UIKit.

In other words, is the concept similar to 'splicing' web site designs? Where a designer draws out the design of the website in something like Photoshop, and then it is cut up into pieces which can be applied to form the actual website? I know this can be done for UIButtons, can this also be done for other controls, and is this how it is usually done?

Or perhaps this is done with Core Animation? I've heard this from time to time, so does this mean that the User Interfaces are 'hard-coded'? Or is Core Animation only use for the 'effects', such as applying the glowing effect to the numbers in WeightBot?

If there are any resources you can point me to I would really appreciate it.

Thanks!