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I'm using Kotlin for Android development. Interesting question. In Java saving Context in static field is a memory leak. But if I'm storing context in Kotlin companion object, Android Studio doesn't say that it's a memory leak. It's means that in Java bytecode conpanion object is not a static code? For example:

class MyApp : Application() {
    override fun onCreate() {
        super.onCreate()
        appContext = applicationContext
    }

    companion object {
        lateinit var appContext: Context
    }
}

Here is no memory leak? Thanks for answers :)

Vladimir Fisher
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  • If you're concerned about a leak you can always use a [`WeakReference`](https://docs.oracle.com/javase/7/docs/api/java/lang/ref/WeakReference.html), which will prevent object from being garbage collected untill all "strong" references are cleared first. – Pawel Aug 31 '18 at 13:49
  • That wasn't the question. – Vladimir Fisher Aug 31 '18 at 14:07

1 Answers1

6

Your code does in fact store a Context in a static way, it's just that lint can't pick it up and warn you for some reason.

In this specific case, however, you're not really at risk of creating a memory leak. You're storing your Application object itself statically, which will be alive for the entirety of your application's life - just like static variables. You'd be in trouble if this was some other, shorter lived Context, but the application Context should be fine.

For reference about whether it's safe to do this:

zsmb13
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  • Thanks for answers! – Vladimir Fisher Aug 31 '18 at 14:09
  • "Note that, even though the members of companion objects look like static members in other languages, at runtime those are still instance members of real objects" - From the docs at https://kotlinlang.org/docs/reference/object-declarations.html So if you do store context behind companion object, under the hood, it's a garbage collectible instance variable. – Mark Lapasa Jan 16 '19 at 05:25
  • Well, yes, but the companion object instance that it belongs to _is_ stored statically. – zsmb13 Jan 16 '19 at 06:11