class screen.Screen(Widget)Screen is an abstract base class for widgets to be uses as screens by a Shell.
- Constructs a Screen associated with the given shell.
- Called from the timer_event() method of the Shell when this screen is the current screen. The default implementation returns true so that a display update is performed.
- Called from the Shell before switching away from this screen to another screen.
- Called from the Shell after switching to this screen from another screen.