Question

Are there any requirements/guidelines for an Android device? like numbers of buttons or minimum buttons required.

Also are there any android devices which do not have the menu and back buttons?

( I am aware that no menu/back buttons will kill most of the apps in terms of usability , I just wanted to know more on the topic 🙂 )

Answer 1

Are there any requirements/guidelines
for an Android device? like numbers of
buttons or minimum buttons required.

Yes. These are documented in the Compatibility Definition Document.

Also are there any android devices
which do not have the menu and back
buttons?

That depends on how you define “buttons” and “android devices”. Quoting from the CDD (see above link):

The Home, Menu and Back functions are
essential to the Android navigation
paradigm. Device implementations MUST
make these functions available to the
user at all times, regardless of
application state. These functions
SHOULD be implemented via dedicated
buttons. They MAY be implemented using
software, gestures, touch panel, etc.,
but if so they MUST be always
accessible and not obscure or
interfere with the available
application display area.

There are devices that do not have dedicated off-screen buttons (whether physical or touch-sensitive off-screen spots). The ARCHOS 5 Android tablet is one — it has the HOME and BACK buttons in an expanded title bar. However, it is unclear if Google considered them to have met the CDD, since the ARCHOS does not have the Android Market. Devices lacking the Market may not meet the CDD.

So, it is entirely possible to create devices that do not meet the CDD, but at that point Android is mostly just another embedded OS, IMHO.