What is the difference between DBAdapter and DAO relevant to Android Apps?

I' m trying to learn what are the patterns that is used to data access in android applications. While reading several source codes in GitHub, tutorials and cookbooks I have found many Android applications use a class called DBAdapter to data operations like CRUD. DBAdapter is similar to DAO(Data Access Object) but DBAdapter don't use an interface to define the methods that is to be implemented. DBAdapter have implemented CRUD related methods as in a class of DAO pattern too. In addition DBAdapter has inner class that is used to create tables of SQLite Database. Is DAO pattern and DBAdapter is same ? If DAO is different how it is different and why Android applications haven’t used DAO pattern ?