6Subclassing UIView and UIScrollView

In previous chapters, you’ve created several views: a UIButton, a UILabel, etc. But what exactly is a view?

  • A view is an instance of UIView or one of its subclasses.

  • A view knows how to draw itself on the application’s window, an instance of UIWindow.

  • A view exists within a hierarchy of views. The root of this hierarchy is the application’s window.

  • A view handles events, like touches.

In this chapter, you are going to create your own UIView subclass that fills the screen with concentric circles, as shown in Figure 6.1. You will also learn how to draw text and enable scrolling and zooming.

Figure 6.1  View that draws concentric circles

In Xcode, select FileNewNew Project.... From the iOS section, ...

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