I am trying to decide where would be the most appropriate place to place a primary action in the main home screen of an Android app. It's a single action, so a Floating Action Button seems suitable, but I am also considering placing the action in the Bottom Action Bar.
Is it common / good practice to have a Bottom Action Bar containing only a single action?
I think this depends entirely on how you want users to behave, and whether or not they are likely to select the option when navigating through different screens of the app.
If users are likely to only need it on one screen, the floating action button would be nice as they user will be able to see more content. But if the user is navigating through the app, it's probably best to keep it in a bottom bar, as it is a constant in the design. See gmail's new material design app for an example.
http://developer.android.com/design/patterns/pure-android.html
Pure Android design guidelines mention not to use bottom tabs for navigation. Another reason not to prefer use of bottom bars in Android is due to its close proximity to device navigation buttons. It could lead to accidental taps.
For a single primary button I think it is a good idea to use a FAB or a button in Action bar.
