Android GUI architecture - relation between Surface/view/window/canvas

Question

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UPDATE: After several days googling and experiments, I have found the answers for most of those dumb questions. See the answers I submitted.

Answer 1

for the question

What is the relationship between an activity and window? Will each Activity has a window?

disagree with @pierrotlefou ,cause in google doc SurfaceView provides a dedicated surface, rather than Window.

The surface is Z ordered so that it is behind the window holding its SurfaceView; the SurfaceView punches a hole in its window to allow its surface to be displayed.