This is something almost all of us know about. We use it, we love it and of course we would like to know about it. Actually it's development requires basic knowledge of java and XML for the basic apps but this is not it. You would require to learn after each and every baby step. Your journey to its top knowledge requires huge number of baby steps. Even google developers don't have the total knowledge in this field.
You can have more information regarding it, visit this google link: Android Development -google