Programming iOS 13

Chapter 12. Controls and Other Views

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 examples in Part III.

UIActivityIndicatorView

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 hidesWhenStopped is true (the default), it is visible only while spinning.

An activity indicator comes in a style; if it is created in code, you’ll set its style with init(style:). Your choices (UIActivityIndicatorView.Style) are:

• .large

• .medium

(Those styles are new in iOS 13, replacing the older .whiteLarge, .white, and gray.)

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 overrides the default gray color of the spokes. An activity indicator is a UIView, so you can also set its backgroundColor; a nice effect is to give an activity indicator a contrasting background ...