How to fix Red "R" squiggly error in Android studio


You can try this;
To fix the XML errors, do a clean/build to fix the issue.
Make sure in your  AndroidManifest.xml the package name is correct.
That fixed the problem for me when 'R' was marked red!
Some Steps

  1. Click on Build
  2. Goto Rebuild Project and then
  3. Click on Tools
  4. Goto Android and sync project with Grade file.