Android WeakReference not behaving as expected

Question

As I know, from the spec (and from the standard non-android) java, If an object is only "Weak Referenced", that is, only reachable by weak references - it will be collected by the garbage collection the next time it runs.

In my android app, for some reason, This is not the case.

A quite heavy object (Activity) stays in the heap every time its created, but when I perform a heap dump and examine it in the Eclipse Memory Analyzer I see that the object remained in the heap, even though it's only weak referenced (as can be seen in merge paths to GC roots option)

When I explicitly clear the weak reference, the object gets cleared.

I run my app on Android 2.3.3. It looks like a some kind of platform bug.

Am I missing something? Has anyone else encountered this issue?

Thanks, Yoav

"I see that the object remained in the heap", what kind of object? Bitmap references? — Blackbelt, Jul 25 '12 at 07:29

score 0 · Answer 1 · answered Jul 25 '12 at 07:04

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it will be collected by the garbage collection the next time it runs.

No, there are no such guarantees. It may be collected. (This holds for all objects, regardless of reference types, and it's the reason why you often read that an object becomes "eligible for collection".)

answered Jul 25 '12 at 07:04

aioobe

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I'm getting an OutOfMemoryError because it is **never** collected – Yoav Schwartz Jul 25 '12 at 07:05
Is it different from what is guaranteed by standard (non-android) java? – Yoav Schwartz Jul 25 '12 at 07:09
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If you get `OutOfMemoryError`s i suggest you use `SoftReference` instead of `WeakReference`. Android tries to clear the `SoftReference`s before throwing `OutOfMemoryException`s and only throws the error if it couldn't clean up enough space. – Adam Monos Jul 25 '12 at 07:34
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Are you saying that android clears SoftReferences **before** WeakReferences? – Yoav Schwartz Jul 25 '12 at 08:17

Android WeakReference not behaving as expected

1 Answers1