Just my 2 cents
Just my 2 cents worth.
So in short to answer OP's question. Not difficult if you don't mind spending some time reading up. First thing I would do differently if I were to do it all over, is get a Java language primer book. Then move into the Android API documentation. From there it's smooth sailing. There may be some books dedicated to priming someone with no Java knowledge to jump straight into Android programming but I'm afraid I don't know the title of any such books myself.
I would have to say having looked at someone else's well written and commented code probably helped me to understand what was going on and how to implement things myself.
Hope this was useful. Sorry this was probably more than 2 cents, maybe a half dollar.