Graphics Programs Reference
In-Depth Information
6
Subclassing 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 applica-
tion'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
