How do I add a library project (such as Sherlock ABS) to Android Studio?
(Not to the old ADT Eclipse-based bundle, but to the new Android Studio.)
I also encountered the same problem then I did following things.
I import the library project into my AndroidStudio IDE as a module using menu File -> Import module menus
Then I went to my main module in which I want the library project as a dependent project
Right click on the main module (in my case its name is app) -> open module setting -> go into dependencies tab -> click on + button (you will get it on right side of window) -> click on module dependency -> select your library project from list
Apply the changes and click the OK button.
It worked for me. I hope it will help others too.