This class provides the fundamental functionality for all UI components. All the built-in components you can add to a Screen are subclasses of the Field class. You cannot create the Field class directly; you must either use one of the implemented subclasses or extend this class to create your own custom component.

In the sample application, the subclasses of the of the Field class are the CustomButtonField, (which you use to create all the custom buttons except for the button with an image as its background), and the PictureBackgroundButtonField class.