The primary feature of the RxAndroid library (https://github.com/ReactiveX/RxAndroid) is that it has Android Schedulers to help your concurrency goals for your Android app. It has a Scheduler for the Android main thread as well as an implementation that can target any message Looper. Striving to be a core library, RxAndroid does not have many other features. You will need specialized reactive binding libraries for Android to do more than that, which we will explore later.
Let's start simple. We will modify TextView in the middle of our MainActivity (which already contains "Hello World!") to change to "Goodbye World!" after 3 seconds. We will do all of this reactively using Observable.delay(). Because this will emit on a computational Scheduler, we will need to leverage observeOn() to safely switch the emission to the Android...
