How the Activity related to Window in Android?

In And开发者_高级运维roid, the concept Window seems not important anymore.

Until recently devices running Android have generally had small displays that would not be able to present multiple "windows" in a usable way. Android best supports display of a single "window" covering the entire screen at any time - along with dialogs for convenience. That window is typically managed by the system at the command of an Activity. So yes .. in general you should forget about windows and use Activities to manage the UI.