I got this error on Android Studio (AS):

I created an
I ran into a similar problem. Looks like my .../src directory for whatever reason moved under my .../lib directory. I moved it out of the /lib directory. Now both /lib and /src are at the same level. After a couple of clean rebuilds and restarts of Android studio everything is back to normal. My emulator started up fine.
You might want to check your directory structure. Compare the directory structure with a working project. You might be able to see the difference.