error: No resource identifier found for attribute ‘adSize’ in package ‘com.google.example’ main.xml

Replace /res/ with /lib/ in your custom layout nampespace.

xmlns:android="http://schemas.android.com/apk/res/android"

in your case, would be:

xmlns:yourApp="http://schemas.android.com/apk/lib/com.yourAppPackege.yourClass"