Getting Started with Core Animation

Core Animation (or Quartz Core) is a library of Objective-C classes built directly into the Media layer of iOS and serves as the backbone for all animations. These animations range from the shaking app icons (indicating a user can rearrange the apps on their home screen) to the sliding animation seen when a user navigates their music library. Unlike Core Graphics, which is confined to a two-dimensional plane, Core Animation also allows for three-dimensional transformations. This makes it easy to implement effects such as the 3D card-flip animation seen in the iPhone’s native Weather app, or the unique page-turn effect seen in the popular Flipboard app for iPad.

Many aspects of Core Animation are accessible through APIs available in UIKit. In some cases, Apple has built specific animations into the base operations of UIKit objects that can be invoked with a single method call. For example, Core Animation powers the modal presentation and the modal transition styles found in UIViewController as well as the pushViewController:animated: method found in UINavigationController. UIKit also facilitates the creation of simple custom animations using methods implemented in UIView. This means basic UIView properties like opacity, bounds, and background color can easily be animated using a series of animation blocks and animation delegate methods.