Is there a source code for the projects in this book (4th edition)?
No, there is no source code available in that edition.
Probably you meant edition 
Yes, there is source code for the projects in the 4th edition book. Here is the download link:
https://www.bignerdranch.com/assets/solutions/AndroidProgramming4e.zip
The link doesn’t work jamie.
Try this one: https://www.bignerdranch.com/solutions/AndroidProgramming4e.zip
The download should start automatically.