If I had my druthers, I'd spend all my time developing mobile apps. I've always been fascinated with pocket-sized computers, and have owned many through the years. Unfortunately, for most of my life such devices have been little more than toys, and so I've had to focus my expertise on writing code for "real computers".
This is true even now, during the explosion of smartphone and tablet usage. I'm one of those dinosaurs who knows how to use C, C++, MFC, ATL, CORBA, UNIX, and other ancient magic, so there are sometimes a few months of old-school development between mobile-development gigs. I write iOS stuff for fun, so I keep those skills sharp, but Android is something I touch only when I'm being paid to do so. Thus, I have to find a way to quickly get back up to speed when the Android work does come.
This is my little refresher for when I arrive back in Android-land. It may not help you at all.
WARNING: The below was written back when I wrote apps that targeted Android 2.x. A lot of it is obsolete with the 4.x API. Someday maybe I'll update this.