Android textview with custom fonts

Hi, I am trying to implement custom fonts in a textview. I have been following cheesebaron's customfont example. I have put all the folders and attributes. But when I compile I am getting the following error:

/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Android/Xamarin.Android.Common.targets: Error: Tool   
exited with code: 1. Output: obj/Debug/res/layout/frglayout.xml:1: error: No resource identifier found for 
attribute 'customFont' in package 'packageName'

Could you please have a look at it. Thanks.