Cannot setup floating action buttons as class cannot be found (Android Studio)

Question

So I am pretty new to android and I am trying to setup a floating action button with the Android Design Support Library using this guide in Android Studio.

My Projec

Answer 1

I had the same problem with Android Studio complaining that it couldn't instantiate FloatingActionButton. The "Exception Details" showed this:

java.lang.IllegalArgumentException: You need to use a Theme.AppCompat theme (or descendant) with the design library.
    at android.support.design.widget.ThemeUtils.checkAppCompatTheme(ThemeUtils.java:33)
    at android.support.design.widget.FloatingActionButton.(FloatingActionButton.java:159)
    at android.support.design.widget.FloatingActionButton.(FloatingActionButton.java:153)

Basically, I was using Material.Light as my theme, but I needed to use an AppCompat theme. I switched to AppCompat.Light and the problem was solved!