Screen Controllers

A screen controller is a Java or Groovy class that contains the screen initialization and event handling logic. Normally, the controller is linked to an XML descriptor which defines the screen layout and data containers, but it can also create all visual and non-visual components programmatically.

All screen controllers implement the FrameOwner marker interface. The name of this interface means that it has a reference to a frame, which is a visual component representing the screen when it is shown in the main application window. There are two types of frames:

  • Window - a standalone window that can be displayed inside the main application window in a tab or as a modal dialog.

  • Fragment - a lightweight component that can be added to windows or other fragments.

Controllers are also divided into two distinct categories according to the frames they use:

  • Screen - a base class of window controllers.

  • ScreenFragment - a base class of fragment controllers.

Figure 16. Controllers and Frames

The Screen class provides the most basic functionality for all standalone screens. There are also more specific base classes to use for screens working with entities:

  • StandardEditor - a base class for entity editor screens.

  • StandardLookup - a base class for entity browse and lookup screens.

  • MasterDetailScreen - a combined screen displaying the list of entities on the left and details of the selected entity on the right.

controller base classes
Figure 17. Base Classes of Controllers