Re: Avoiding Running Out Of Memory

Kevin McMurtrie <>
Sun, 06 Mar 2011 10:07:30 -0800
In article <ikvoq9$20t$>,
 Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> wrote:

I???ve implemented a simple picture picker widget in this Android app I???m
working on. Here???s the guts of the code that initializes it:

        final String ExternalStorage =
        final String[] Places =
        for (String Place : Places)
            final ThisDir = new;
            if (ThisDir.isDirectory())
                for ( Item : ThisDir.listFiles())
           ThisImage =
                    if (ThisImage != null)
                        ThePics.AppendItem(ThisImage, Item, Item.getName());
                      } /*if*/
                  } /*for*/
              } /*if*/
          } /*for*/

The first time after the app was launched, bringing up the picker would
work. But on the second time, the app would crash with
???java.lang.OutOfMemoryError: bitmap size exceeds VM budget??? in

Even rotating the phone (which causes the re-creation of the activity)
triggered the crash.

Just to make it clear, the widget does NOT keep a reference to the Bitmap
that is passed; it creates a copy, scaled as necessary so as not to exceed a
maximum thumbnail size (160x160 pixels). So each thumbnail should take no
more than about 100K max, and my phone only has about a dozen pictures on

I went over the ???Avoiding Memory Leaks??? article
looking carefully for unwanted references that might be preventing bitmaps
from being freed.

Finally, one simple change did the trick: after that ThePics.Append call
above, I added


and that fixed it! Now I can bring up the picker multiple times during a
single app invocation, rotate the phone any number of times I like, and it
all works nicely.

So the question is: why was the garbage collector being so tardy in
reclaiming all those loaded full-size images?

Native memory held by Java objects is freed by Finalizer threads or
system graphics threads watching a ReferenceQueue. It's one step behind
collections. Since the JVM can't track native memory, GC may give up on
the belief that additional collection cycles are futile.

If you can access the image as a raster, you may be able to perform
simple 1/n scaling before performing a resample to an exact size. For
example, scale 4368x2912 by 1/10 to 437x291 then resample to 160x107.
It's possible to perform anti-aliased resampling on a raster too but
it's very heavy in floating point math.
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