Cannot resolve symbol DrawerLayout

I'm trying to implement the Navigation Drawer as shown here: http://developer.android.com/training/implementing-navigation/nav-drawer.html#top

My code seems to be ok, and My minimum and target levels in my manifest match the example, but it's telling me it can't find the following three references

import android.support.v4.app.ActionBarDrawerToggle;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;