Android: UI Recommendations about Exit button in Applications

Question

Are UI recommendations or guidelines somewhere. I am looking for the recommendation from Google but unfortunately I can't find it. I want to see something like "...do not use exit button in your Applications until you really need it...". I'm sure that the exit button in android app is not good idea, in general at least. But I want to prove this idea to customers and designers.

I need links with explanations.

Answer 1

This video will help your customers to understand: https://www.youtube.com/watch?v=631T7B8HOv4

Basically, the back button is an exit button. So, there is already an exit button!

Show it to your customer and ask him if he wants to look stupid with duplicate button that takes precious space on a small screen.

His app will never look professional.

Answer 2

General Design Guidelines: http://developer.android.com/design/get-started/principles.html

Best Practices for User Experience & UI: http://developer.android.com/training/best-ux.html

Providing Proper Back Navigation(Something you were looking for): http://developer.android.com/training/implementing-navigation/temporal.html