17.14. Animating and Moving Views
You want to animate the displacement of views.
Use the animation methods of
UIView while displacing your views.
There are various ways of performing animations in iOS: capabilities are provided at a relatively low level, but also at a higher level. The highest level we can get is through UIKit, which is what we will be discussing in this section. UIKit includes some low-level Core Animation functionalities and presents us with a really clean API to work with.
The starting point for performing animations in UIKit is to call the
context: class method of the
UIView class. Its first parameter is an
optional name that you choose for your animation, and the second is an
optional context that you can retrieve later to pass to delegate methods
of the animations. We will talk about these shortly.
After you start an animation with the
beginAnimations:context: method, it won’t
actually take place until you call the
commitAnimations class method of
UIView class. The calculation you perform on a
view object (such as moving it) between calling
commitAnimations will be animated after the
commitAnimations call. Let’s have a
look at an example.
As we saw in Recipe 17.4, I included in my bundle an image called Xcode.png. This is Xcode’s icon, which I found by searching in Google Images (see Figure 17-14). Now, in my view controller (see Recipe 17.0), I want to place this image in an image view ...