Android Studio “cannot resolve symbol” but project compiles and works

Question

The project compiles fine. However, Android studio 3.0.1 shows reference to one particular library in red and displays \"cannot resolve symbol\". Even single stepping into

Answer 1

This is happen to me when I move my project to other pc or open the project with other pc and with different SDK folder location. Solution: close project, delete folder .gradle and folder .idea inside project folder then open your project to sync gradle.