John Petitto About Blog

Fragments, Don’t Hurt Me

Here’s a screen I was recently working on for an app at work:

It’s built with a Fragment containing a ViewPager. Each page in the ViewPager is served by a FragmentPagerAdapter. Pretty straight forward stuff.

On first launch it works as expected, but if the enclosing Activity is destroyed, no pages get recreated by the FragmentPagerAdapter.

The Silliness of Nullability and Views

Since Google introduced the support annotations library, there’s been an increase in the application of the @Nullable and @NonNull annotations in APIs. It’s helpful in languages such as Java where optional values are not first class citizens. Static analyzers can infer at compile time if an object has the possibility of being null when passed to (or returned from) a method.

While the benefits of these annotations can certainly be helpful, they may also hinder users of an API. A great case in point would be that of the findViewById method in Android’s ActivityAppCompat class:

Loading Resources from Unit Tests

There are a handful of reasons why you’d want to load in a resource file for a test:

  • Input (or output) data is large and complex
  • Input (or output) data is not easily mockable, such as a File or InputStream
  • Configuration data is preferably externalized

One option would be to place your resources in your app’s /res or /assets directory. This requires instrumenting your tests so that you can access the resources through the app’s Context. This can be undesirable for two reasons:

RxJava for Android Developers (Talk)

Last week I gave a talk on RxJava at the Austin Droids meetup. It marked the group’s fifth year in existence (congrats to the organizers!) and was also the most attended meetup in its history. I was hoping to have the talk recorded but after some technical issues we weren’t able to make it happen. I posted the slides online after the talk but I don’t think they stand too well on their own. So I’ve taken the time to write out my narrative to the slides below.