Check out SYSTEM_UI_FLAG_HIDE_NAVIGATION, this flag hides the navigation bar until the user interacts with the device. It was introduced in Android 4.0. You can enable this flag for example like this:
Note that the navigation won't disappear again automatically, you have to set it every time after the user interacted with the device.
Alternatively you can make the navigation less obtrusive by using SYSTEM_UI_FLAG_LOW_PROFILE, this changes the buttons into small dots (e.g. like the camera app).
We've tried this. The ApiDemos for Ice Cream Sandwich have a screen that cycles through the different options for SystemUiVisibility. Nothing happens when we try SYSTEM_UI_FLAG_HIDE_NAVIGATION. Do you think this behaviour may be device dependent? We tried it on an Asus Transformer Prime.
I just tried it in the emulator, it works there as described. I only own a old HTC desire with hardware keys right now, so I can't test it on a real device. Might be device dependend, can't say for sure.
Works but from docs "There is a limitation: because navigation controls are so important, the least user interaction will cause them to reappear immediately." i.e. as soon as user touches screen, they pop back.
you can also change your SDK version, for example, to <uses-sdk android:minSdkVersion="7" android:targetSdkVersion="17"/> and it won't show