R cannot be resolved - Android, no import android.R; statement

Question

Ok, I am working on a new app and everything worked fine as long as I used a Relative View. However, I want a tabbed layout so I switched what I had (not much so far since

Answer 1

In my case it was caused since I refactored my project and moved some classes inside a folder structure. Those classes couldnt find the R as usual, since its based on the root source folder.