solve error: cannot access Publisher in Android Studio?

Question

I am getting this error while compilation of my code:

Can anyone help me how to solve this error or what might be causing this error?

Edit1: Gradle

Answer 1

in my case the Publisher class was belong to the RxJava library which was missing from my project so adding these two lines in my app/gradle file fixed the problem:

implementation 'io.reactivex.rxjava2:rxandroid:2.1.1'

implementation 'io.reactivex.rxjava2:rxjava:2.x.x'