It may be useful for a screen to have access to it's containing display
How the screen should be drawn Drawing of screen components is handled after this method
How the screen should respond to events Is necessary because it is an event handler
What the screen should do every screen update If the renderer is on VSync, update may be called more than once per actual frame Can be treated as the insides of a while(true) loop
All the components that the screen contains; components are handled separately from the screen
The display that contains this screen
An object that represents an Activity or a Screen or a point in time of the display Draws itself to the screen, can handle events, and can contain components which do the same Adding components to an activity ensures that they will automatically get handled as long as the activity is active