CODEWITHSUNDEEP
androidmemory-managementgarbage-collection
Aurelius Schnitzler
Aurelius Schnitzler

Reputation: 531

Does android have a garbage collection and how quick is it?

Does Android have a Garbage Collection? Is it efficient or should you set objects to null when not needed?

For example, I have an ImageView iv. I set an image bitmap with

iv.setImageBitmap(some_function_that_returns_a_bitmap_that_is_newly_created())

and after some time I run the same function

iv.setImageBitmap(some_function_that_returns_a_bitmap_that_is_newly_created())

What happens to the Bitmap that was created by the first function some_function_that_returns_a_bitmap_that_is_newly_created()? Does the garbage collection remove it? Does it make a difference, to do this

Bitmap temp =some_function_that_returns_a_bitmap_that_is_newly_created();
iv.setImageBitmap(temp);
temp = null;
...
temp =some_function_that_returns_a_bitmap_that_is_newly_created();

instead?

Does it make a difference, to do this

Bitmap temp =some_function_that_returns_a_bitmap_that_is_newly_created();
...
temp = null;
...
temp =some_function_that_returns_a_bitmap_that_is_newly_created();

instead of this

Bitmap temp = some_function_that_returns_a_bitmap_that_is_newly_created();
...
temp = some_function_that_returns_a_bitmap_that_is_newly_created();

?

Upvotes: 1

Views: 420

Answers (1)

G. Blake Meike
G. Blake Meike

Reputation: 6715

Yes, Android's VM does garbage collection. There are very, very few places where nulling the reference to an object is an effective way to save space... but you've hit one of them.

Bitmaps are large and it, very definitely, can be helpful to null a reference to one that you no longer need.

In the code that you show in the second example, your intuition is correct, the reference to the old bitmap will keep it from being recycled until the reference to the new bitmap is assigned to temp. That means that at some point, both are in memory.

The first version of your code does not have that problem.

Edited to add: btw, standard practice in Java is camelCasing, not under_scoring ;-P

Upvotes: 1

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