Java files have a red circle with J in it (android studio) [duplicate]

Question

I downloaded a project from GitHub, in which me and a friend are working on. Everything was working fine and all of a sudden a red circle with a "J" in it was on the Java files' icons and the run app button become grayed out. Please help me!

Answer 1

I hope you have already found a workaround, but if not/for future reference:
I assume we 're talking about this icon: .
If this answer (or this post) don't seem to be a solution for you, then you should probably go for Configuring Content Roots (docs based on IntelliJ, but this answer should conform the docs to Android-Studio).