I have been fairly frustrated with a gap in the Android documentation recently - the file formats for creating Drawables from XML. Drawables XML has been pretty useful to me in the past in creating gradients; I'd rather use it than create 9-patches all the time. However, the Android documentation is strangely silent about the format; they provide a few samples, but as far as I know there's nothing beyond that.
I've taken it upon myself to study the source code and create a missing manual for all the possibilities for Drawable XMLs. The data was gathered from the Android source code, from the android.graphics.drawables package. I was surprised to find a lot of really useful code I wish I'd known about a long time ago; regardless, I was able to figure out all of how Drawables XML works.
Without further ado, here it is: the missing manual on Android Drawables via XML. I hope this lessens the pain someone else has slightly.