"Couldn't resolve resource" in Android Studio's Preview
The only reliable way I've found so far is reloading the project / restarting Android Studio.
Quickest way to do that is File → Invalidate caches / Restart... → Just Restart.
Feel free to post better solutions!
you DO NOT need to close the entire project. It's just way too much for so little problem.
Just refresh the preview (click the "refresh" button)
provided from https://stackoverflow.com/a/34754707/3339597
Right click on project and Synchronize '...Project' worked for me.