I will be teaching a course on Android App development next term at Lane Community College. You will learn how to build apps using both Android Studio and Java (the standard way to make apps) and using the Xamarin framework and C# to make cross-platform apps. The course starts January 8, 2018. Registration is open now. There are both on-campus and online sections of the class. You can read more here: https://birdsbits.wordpress.com/2014/09/09/xamarin-android-course