If you are targeting iOS7 and already have the image split into frames you can use animatedImageNamed:duration:
.
Let's say you are animating a spinner. Copy all of your frames into the project and name them as follows:
spinner-1.png
spinner-2.png
spinner-3.png
Then create the image via:
[UIImage animatedImageNamed:@"spinner-" duration:1.0f];
This method loads a series of files by appending a series of numbers to the base file name provided in the name parameter. For example, if the name parameter had ‘image’ as its contents, this method would attempt to load images from files with the names ‘image0’, ‘image1’ and so on all the way up to ‘image1024’. All images included in the animated image should share the same size and scale.