Programming iOS 4

Part IV. Views

This part of the book is about the things that appear in an app’s interface. All such things are, ultimately, views. A view is a unit of your app that knows how to draw itself. A view also knows how to sense that the user has touched it. Views are what your user sees on the screen, and what your user interacts with by touching the screen. Thus, views are the primary constituent of an app’s visible, touchable manifestation. They are your app’s interface. So it’s going to be crucial to know how views work.

• Chapter 14 discusses views in their most general aspect — their hierarchy, position, and visibility.
• A view knows how to draw itself. Chapter 15 is about drawing; it explains how to tell a view what you want it to draw, from simply displaying an already existing image to constructing a drawing line by line.
• The drawing power of a view comes ultimately from its layer. To put it another way, a layer is effectively the aspect of a view that knows how to draw — with even more power. Chapter 16 explains about layers.
• A iOS app’s interface isn’t generally static; it’s lively. Much of that liveliness comes from animation. iOS gives you great power to animate your interface with remarkable ease; that power resides ultimately in layers. Now that you know about layers, Chapter 17 tells about animation.
• A view knows how to draw itself; it also knows how to sense that the user is touching it. Chapter 18 is about touches. It explains the iOS view-based mechanisms for sensing ...