Nov 13, 2015
Nov 14, 2015 (Retired)
py - Pierre Yves Ricau (pyricau)
py - Pierre Yves Ricau (pyricau)
Evelio Tarazona (eveliotc)
Michael Prentice (Splaktar)
Source code
APK file



An enum based library to replace fragments, because #perfmatters.

“Frag your app complexity today!” - Zach K.

We all know that Fragments suck, and that #enumsmatter. What if we could replace Fragments with Enums?

What's Fragnums?

Fragnums is the smallest, simplest and most performant Android backstack library:

  • No reflection, unlike Fragments which are recreated through reflection.
  • Each enum value is both a screen and a presenter. This means only one instance of each value is created, ever. No useless garbage collection!
  • Synchronous transitions coz ain't nobody got time for Async Fragment Transactions.
  • Handles configuration changes, for all the landscape nut lovers out there.

Show me the code

Creating a new screen is as simple as adding an enum value:

  MY_SCREEN(R.layout.my_screen_layout, R.string.my_screen_title) {
    @Override protected void onBind() {
      View button = findViewById(;
      button.setOnClickListener(new View.OnClickListener() {
        @Override public void onClick(View view) {
          // Do something.

Then you can just do goTo(MY_SCREEN).

Getting started

  • Copy the three classes from the example.
  • You're good to go! You can now focus on writing new screens and features, just by adding new enum values.

Why should I use Fragnums?

  • Ultra small footprint: no dependency. In fact, it's not even a library, just three classes to copy.
  • It's really hard to test, so test zealots can't force you to write tests. You can therefore focus on writing more features.
  • All your business logic is in one place, so it's really easy to have a 30,000 feet picture of your code. We suggest you start using a smaller font size in your IDE.

How does it work?

Is this serious?

No. The core principles are good, but this is a satire library. Read the code and see for yourself.

More details

  • The suggestion that we should stop using enums because #perfmatters is a fallacy. An enum is essentially a class. Every new class makes our binary a bit bigger and our runtime a bit slower. Should we stop using classes? Or should we instead focus on the perf problems that actually matter?
  • This library shows how to implement a very basic backstack. You don't need enums for that, you could have a Screen class instead.
  • It's cool to know that one could make an enum centric app. However just because you can, doesn't mean you should.
  • If you're into trolling at conferences, you can get the #enumsmatter T-Shirt here. I am not affiliated with this T-Shirt campaign.