Android Studio 3.0 cannot resolve symbol Theme

Question

As stated in style.xml, there is a weird error, which shows Cannot resolve symbol \'Theme\', which is quite strange.

See pic of the error :-

My Project Spe

Answer 1

Had the same issue after upgrading to Android Studio 3.1 (EDIT: bug still present at v3.1.3). What worked for me was clicking File > Close Project and then reopening the project from Studio's dialog.