今さら聞けない | #iOS | #Android ファショ通

... @Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { super.onActivityResult(requestCode, resultCode, data); Fragment fragment = getFragmentManager().findFragmentById(R.id.your_fragment_id); if (fragment != null) { fragment.onActivityResult(requestCode, resultCode, data); } } ...

こんな記事を見かけた.

Why don't you use enum ? // Speaker Deck

...
public class Status {
  public static final int OK = 0;
  public static final int ERROR = 1;
}

public void onSomethingAction(int status) {
  switch (status) {
    case Status.OK:
      Log.d(TAG, “Status : OK”);
      break;
    case Status.ERROR:
      Log.d(TAG, “Status : NG”);
      break;
  }
}
...

より,

...
public enum Status {
  OK,
  ERROR
}

public void onSomethingAction(Status status) {
  Log.d(TAG, “Status : “ + status.name());
}
...

のほうがいいよね, と.

なんとなくここら「enum」についての議論を
よく見かけたような気がしたのですこし調べてみる.

even in the most recent documents android suggests that it's not such a good idea to use enums in an android application. The reason why is because they use up more memory than a static constants variable.

Working with Enums in android - Stack Overflow

Enums often require more than twice as much memory as static constants. You should strictly avoid using enums on Android.

java - Why Android uses Ints instead of Enums - Stack Overflow

Android_Memories____Speaker_Deck

Android Memories // Speaker Deck

公式ドキュメントには,

Be aware of memory overhead
…
Enums often require more than twice as much memory as static constants. You should strictly avoid using enums on Android.
…

Managing Your App's Memory | Android Developers

と書いてる.

他に,

Java enums are tremendously more expensive in code size than simple static final ints; classes and objects have not-insignificant overhead, so if you take a very class-heavy approach to your implementation you can end up with a significantly larger code size and RAM footprint for your app.

I really like this article on the importance of thinking about performance…

これに対して Jake Wharton さんも言及.

If you use integer constants instead of enums in your Android app you are a fool. @mttkay's reply here is spot-on: https://t.co/ByedAuLTi1

— Jake Wharton (@JakeWharton) 2015, 1月 4

他には,

Should I strictly avoid using enums on Android?
No. Strictly means they are so bad, they should not be used at all. Possibly a performance issues might arise in an extreme situation like many many many (thousands or millions of) operations with enums (consecutive on the ui thread). Far more common are the network I/O operations that should strictly happen in a background thread. The most common usage of enums is probably some kind of type check - whether an object is this or that which is so fast you won't be able to notice a difference between a single comparison of enums and a comparison of integers.

java - Should I strictly avoid using enums on Android? - Stack Overflow

the original version of that document was just a bunch of prejudices. it's been rewritten to only contain facts backed up by actual benchmarks, and it's updated as the VM is updated. you can find the various benchmarks

Why was "Avoid Enums Where You Only Need Ints" removed from Android's performance tips? - Stack Overflow

結局,