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 has happened to me a couple of times, there are a few ways you can resolve this problem;

1. Sync project files with gradle in the File toolbar
2. Use the Invalidate/Restart option in the File toolbar to invalidate the caches.
3. Delete the .idea folder and restart Android Studio

Answer 2

For me problem was that AS suggested I upgrade gradle version, (from 3.5 to 4.4), and then it started doing it.

Solution was to delete the 3.5 folder from .gradle in project

Answer 3

None of the answers worked for me

Fixed it by:

1. Removing & adding all java files via Project window on the left side of Android Studio

2. Commenting/un-commenting & syncing libraries in the gradle file in small groups.

And cleaning all caches before that (as part of other fixes here).

Answer 4

Following has resolved this for me.

1. remove library from gradle cache (in case of linux, it's in ~/.gradle/caches).
2. remove library dependency from the build.gradle and sync
3. restart (maybe invalidate cache)
4. add library dependency to build.gradle and sync
5. clean and rebuild

Answer 5

Tried all of the above but nothing worked.

Got Solution by: 1. Updating Android studio to latest version 2. Updating the Gradle version to latest one

Answer 6

I've tried Invalidate Caches/Restart..., tried manually delete .idea and .build folders and it didn't work for my case. I using VCS (git) and I just commit my changes, removed the whole project, and Checkout from Version Control. It fixed this problem.

Android Studio 3.6.3