Android Development

What the FlatMap?

Understand flatmap in RxJava

3 minute read

The operator flatmap in RxJava is a tough topic if you are not familiar with functional style. After reading all the articles and tutorials and even worked with RxJava for almost a year, I’m still not quite confident about it. I sure know how to and when to use it, but the understanding seems always shallow. Until I read the flatmap in the Structure and Interpretation of Computer Programs.

How to write maintainable RecyclerView

Write maintainable RecyclerView in Android

6 minute read

Google is famous for making complicated things. RecyclerView is not an exception. It is more flexible than the previous ListView I understand, but that also means that us developers need to understand more and do more work. I have seen gigantic adapters that have very complicated logic especially when there are multiple types that the RecyclerView is trying to handle. I think I happen to know one way to organize things a bit better so one can easily find what he/she is looking for.

Customize Android Seekbar Color

How to customize the colors for android seekbar

1 minute read

I was tasked to create a simple media player app for a shop demo, and I’m using the built-in SeekBar for the volume control. All goes well, until I want to change the color of it. The design has it like the thumb of the SeekBar is white, and first half is green and rest half is grey. It took me almost a whole day to find a satisfying anwser, come on Android!

2 minute read

Android Espresso Testing

In previous article, we talked about how to scroll to a certain position in RecyclerView in the test. In this article, we further discuss how to write a custom matcher and use it to scroll the RecyclerView. Let’s say that we want to scroll to certain item in RecyclerView, but we don’t know the position. We can then create a custom Matcher, and use the matcher to determine which item to scroll to.

1 minute read

Android Espresso Testing

In part II, we wrote a test case to verify that the app can create a task and the task will be seen on the screen. In this part III, we will demonstrate one technique on writing tests that involves a RecyclerView. First we repeatly add some tasks, and then we verify that the last added task is on display. Note that since we are using a RecyclerView, the last item might not be seen, so we need to scroll the RecyclerView before checking.