Programming iOS 9

Part I. Views

The things that appear in your app’s interface 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 1 discusses views in their most general aspect — their hierarchy, visibility, and position, including an explanation of autolayout.
• Chapter 2 is about drawing. A view knows how to draw itself; this chapter explains how to tell a view what you want it to draw, from displaying an existing image to constructing a drawing in code.
• Chapter 3 explains about layers. 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 4 tells about animation. An 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, it turns out, resides ultimately in layers.
• Chapter 5 is about touches. A view knows how to sense that the user is touching it. This chapter explains the iOS view-based mechanisms for sensing and responding to touches, with details on how touches are ...