If you haven't tried already, you might attempt to use the View
flag for hiding navigation, SYSTEM_UI_FLAG_HIDE_NAVIGATION
, documented here.
However it may be important to note this found at the bottom of their description :
There is a limitation: because navigation controls are so important, the least user interaction will cause them to reappear immediately. When this happens, both this flag and SYSTEM_UI_FLAG_FULLSCREEN will be cleared automatically, so that both elements reappear at the same time.
which is probably related to what you're seeing. I find it hard to believe there's a way around this... I just tried and every fullscreen app I have on my S3 behaves this exact same way.
I suspect that if there was a way around it (assuming the above doesn't work, which I don't expect it to), it would be considered to be a bug by the Android team, and I would advise against it.