I have the following error in my preview window in the latest version of Android Studio (1.2) that stops me from being able to view the layout I am creating
You can also update Gradle to version 1.2.3 as explained here: https://code.google.com/p/android/issues/detail?id=171417
Apparently this was a bug on version 1.2.2 of Gradle and from the next version of Android studio Gradle 1.2.3 will be the default on new projects.
At least it worked for.
While Base.Theme.AppCompat.... is the superclass of Theme.AppCompat.... anyway, I prefer the fix using the new version of Gradle.
Worked for me, hope it works for you.
Also I had to Clean and Rebuild the Project.