Peter --
I don't want to exit. I want to make the same action as Android, when you have one activity and press back button.
Typically it's not neccessary to process something - activity becomes background, the app is alive.
In my case sequence is following. Initial activity (A) calls real main activity (B) and dies (I don't need activity A any more, so I execute Activity.Finish).
Problem happends in activity B, when user clicks "Back". When I do not process KeyPress, dead activity A appears. Meanwhile I want to send activity B to sleep. Something like SleepActivity (B). But how ?