Screens in Blackberry

The main component of a BlackBerry device UI is the Screen object.

Screen classes

Screen	You can use the Screen class to create a screen and use a layout manager to lay out the UI components on the screen. You can define a specific type of screen by using the styles that the constants in the Field superclass define.
FullScreen	You can use the FullScreen class to create an empty screen to which you can add UI components in a standard vertical layout. If you want to use another layout style, such as horizontal or diagonal, you can use the Screen class instead and add a layout manager to it.
MainScreen     PopupScreen	You can use the MainScreen class to create a screen with the following standard UI components: default screen title, with a SeparatorField after the title main scrollable section contained in a VerticalFieldManager default menu with a Close menu item default close action that closes the screen when the BlackBerry device user clicks the Close menu item or presses the Escape key You should consider using a MainScreen object for the first screen of your BlackBerry device application to maintain consistency with other BlackBerry device applications. Screen providing features for building dialog and status screens