After few more months working at nights, while commuting and weekends, I managed to write a book specialised on Android Custom Views.
It covers several topics: first it explains the reasons why we need to build custom views and what are the benefits and drawbacks of using them and then, describes how to start drawing our first shapes, add animations and user interactions and do some more complex rendering or create 3D custom Views in OpenGL ES. Finally, it also shows how to share and publish our custom View and how to optimize it for performance.
It’s available as ebook and printed format and, if you’re interested, you can grab a copy in amazon:
or alternatively:
https://www.packtpub.com/application-development/building-android-uis-custom-views
http://shop.oreilly.com/product/9781785882869.do
https://www.kobo.com/us/en/ebook/building-android-uis-with-custom-views
This is a rather advanced book and requires some basic knowledge of how Android works. If you want to learn how to develop applications for Android I recommend to start with my previous book (maybe no longer in 2021 - look for updated alternatives 😎)