In AndroidManifest.xml fix analyzer warning by specifying targetSdkVersion.
In NotesDataSource.java fix Analyzer warning possible NullPointerException. If notePrefs.getAll() returns null, set notesMap to an empty map.
In strings.xml add action_create.
Add res/menu/menu.xml and in NotesActivity.java override onCreateOptionsMenu() to inflate menu.

Now "+" icon shows in action bar, but tapping it doesn't do anything yet.