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I'm struggling with conceptualizing animations with a CALayer as opposed to UIView's own animation methods. Throw "Core Animation" into this and, well, maybe someone can articulate these concepts from a high level so I can better visualize what's happening and why I'd want to migrate UIView animations (which I'm quite familiar with now) to CALayer animations on the iPhone. Every view in Cocoa-Touch automatically gets a layer. And, it seems, you can animate one and/or the other?!? Even mix them together?!? But why? Where's the line? What's the pro/con to each?
The Core Animation Programming Guide immediately jumps into Layer & Timing Classes and I think need to take a step back and understand why these varied pieces exist and how relate to each other.
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Working with UIViews happens on the main thread, it means it is using CPU power. CALayer: Layers on other hand have simpler hierarchy. That means they are faster to resolve and quicker to draw on the screen. There is no responder chain overhead unlike with views.
The contents of your block are performed on the main thread regardless of where you call [UIView animateWithDuration:animations:] . It's best to let the OS run your animations; the animation thread does not block the main thread -- only the animation block itself.
UIView. animate runs on the main thread and is asynchronous.
On iOS, views always have an underlying layer. There is a very strong relationship between the view and its layer, and the view derives most of its data from the layer object directly.
Use views for control and layers for eye candy. Layers don't receive events so it's easier to use a view for those cases, but when you want to animate a sprite or backgrounds, etc., layers make sense. Events pass right through layers to the backing view so you can have a pretty visual representation without messing up your events. Try to overlay a view that you're just using for visual representation and you'll have to pass tap events through to the underlying view yourself.
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