In order to improve my skills on android development I always search for sample code and valueable apps from which learning new things. Here is my list of android apps I found with source code available. This post has been inspired from this article about great android apps that are also open source.
Philm is a movie collection and information app created for Android by Chris Banes. It uses the Trakt and TMDB APIs.
Very nice and usefull note taking application developed by Federico Iosue.
Implementation of Instagram with Material Design (based on Emmanuel Pacamalan’s concept).
Google I/O App
The Google I/O App is the official app intended to help you navigate the conference, whether you’re attending in-person or remotely. The other primary goal of the app is to serve as a practical example of best practices for Android app design and development.
Wordpress for Android
The power of WordPress.com and self-hosted WordPress.org sites on your hands.