Choose another theme (other than Holo, for example Theme)
When you create the style incorrectly or from an existing style, this problem usually occurs. So select the “Graphical Layout” select “AppTheme” (The tab with a blue star). And select any of the predefined style. In my case “Light” which should resolve the problem.
Try to ‘Invalidate caches & restart’.
Restart your Android Studio by choosing this option. It may take some time.
Then, if still doesn’t work try to rebuild your project.