Android Studio 2.1 Cannot resolve symbol 'R'

Question

Android Studio 2.1, Java V8 Update 91, Gradle 2.1.0 .

I know that this questions has been asked many times here, but none of the recommendation solutions works out.

Answer 1

I try to change the Gradle version from 2.1.0 to 2.0.0, even in AS ver 2.1, ignoring the Instant Run performance and its work out. The little R error is now gone. Now, I tried to change back to 2.1.0, the R error also gone..!! Sometime this little thing drive me crazy, a bit.

Shame on me.