Android studio refactoring fail (read-only)
this can be solved go to: on the righ corner find gradle ---> :app ---> other ---> clean
after successful cleaning
dont rebuild the project yet
after cleaning do a refactor rename
start your app again.
Beta 3 was "recalled" due to a bug they found after the release. Check this for reference. You should revert to Android Studio 3 beta 2 and it may fix the problem. Beta 2 can be downloaded from the Android Studio website. The bug itself appears to be affecting both Beta 3 and 4. There isn't much to do about it, and reverting to beta 2 still looks like the best option as of now. Beta 5 may fix it, but there is no way of knowing.
The bug has since been fixed in beta 5, according to the issue tracker.