What are the UX design considerations when placing all navigation and action controls of an Android app in the Main Action Bar?

Question

Google's Android design guidelines include detailed information regarding Layout Considerations for Split Action Bars. While it doesn't seem to go aligned with the guidelines, some apps have ALL their controls (navigation and action buttons) placed in the Main Action Bar. See for example the UI of Twitter for Android and Dropbox.

What's the rationale behind following such approach? Obviously you earn more screen space by doing so, but is it considered a good practice in terms of navigation and app's actions layout?

Answer 1

This question made me think and revisit some of the apps using this pattern to look specifically for any Usability issues. Some more include - Facebook Messenger, Tumblr, Swarm by Foursquare.

When I had first seen these apps they seemed odd to me as an Android UX designer who is aware of Android guidelines. But I don't think they pose any major usability concerns (though a heuristic that it could violate is consistency).

While taking this design approach (of using Action bar for navigation) an important point to consider would be to define place for contextual actions. One way is to use a Floating Action Button on that page (As in Tumblr). But then there can be only one such button on a screen. Another approach is as in Facebook Messenger that uses a bottom bar for contextual buttons.

Also it might be useful to use the Action bar to describe each screen as in Facebook's primary app.

I think going forward as more apps are released with emphasis on content first approach instead of deep navigations, the Action Bar would become less specific. In fact Google Fit does not have an Action Bar and most of the functionality is available through Action Overflow.

Answer 2

When releasing our company's app, we had a Google consultant coming in and talk to us about exactly this issue - the app was designed BEFORE material design.

We were asked to consider the following questions/thoughts:

• Do the action bar items open a drawer or a side pane? If yes: Do not place them in the action bar.
• Is the action of the item you want to put in the action bar primary or secondary? If secondary: Move it to the drawer.
• If you are designing a multi-device-app, so for tablets and mobiles, make sure the room you plan for your nav items is sufficient. If the device is not capable of taking all items in a row, the native behavior is to break them to the footer bar. This is hardly controllable behavior and will have a major influence on usage of primary actions. Make sure to understand the positioning of the nav items caused by different device usage.
• Are the nav items of the same priority weight? E.g. a cart and a "show previous orders" item are uneven: The cart is more important for the app structure. Remove the "previous order" item then.
• If the item is a primary action: Do not put it in the drawer. This will have an implication on which items can be placed in the drawer after this decision, because then it will be en pair in terms of priority with other items.
• Are the main navigation items separate functionalities, or is there a nested dependency? E.g. "Category overview" and "Category 1" should not be in the action bar together, since this would mix hierarchy levels.
• User account information, logout, terms of service, data security information, help desk, etc. Google asked us to put that in the drawer.

I think you get the point. For us, it mostly broke down to the "prioritization" question.