The Android developer website is Google’s official reference for people who are creating apps for Android devices. With a few exceptions, it is not set up as a learning resource, however, there are helpful links and there is tons of information. Primarily, the developer site is meant to be used for looking up specific information as it is needed. In other words, most of the time, it is meant to be searched, not browsed. If you have specific questions for a project this is the place to go to find an answer.
Design – This section of the developer site deals with designing user interfaces for your apps. It has lots of information and resources for getting started and developing good habits.
Training – Here, you will find a plethora of useful resources for learning about how to create apps.