This chapter discusses all UIView subclasses provided by UIKit that haven’t been discussed already. It’s remarkable how few of them there are; UIKit exhibits a notable economy of means in this regard.
Additional UIView subclasses, as well as UIViewController subclasses that create interface, are provided by other frameworks. There will be lots of examples in Part III. For example, the Map Kit framework provides the MKMapView (Chapter 21); and the MessageUI framework provides MFMailComposeViewController, which supplies a user interface for composing and sending a mail message (Chapter 20).
An activity indicator (UIActivityIndicatorView) appears as the spokes of a small wheel. You set the spokes spinning with
startAnimating, giving the user a sense that some time-consuming process is taking place. You stop the spinning with
stopAnimating. If the activity indicator’s
true (the default), it is visible only while spinning.
An activity indicator comes in a style, its
activityIndicatorViewStyle; if it is created in code, you’ll set its style with
init(activityIndicatorStyle:). Your choices (UIActivityIndicatorViewStyle) are:
An activity indicator has a standard size, which depends on its style. Changing its size in code changes the size of the view, but not the size of the spokes. For bigger spokes, you can resort to a scale transform.
You can assign an activity indicator a
color; this ...