Question

Memory Issues

So I am writing an app that should be able to page through detail views that have one large 640 x 480 image on top and 3 images that are part of a gallery that is being lazy loaded. Following Google design guidelines this is what they suggest doing. I can page through maybe 12 – 13 fragments before it crashes because of being out of memory. I think that there are a couple of culprits in this problem.

1.) I am using the FragmentStatePager. Shouldn’t this be destroying the fragments that are not being viewed when memory becomes an issue? This is not happening. I thought it was automatic. What do I have to do to make this happen? Could it have something to do with how I have my Fragment implemented? I do all of my Activity config in onCreateView. For the sake of thoroughness I’ve included the source for this. Plain Vanilla here:

public static class MyAdapter extends FragmentStatePagerAdapter {


        public MyAdapter(FragmentManager fm) {
            super(fm);              
        }

        @Override
        public int getCount() {
            return NUM_ITEMS;
        }

        @Override
        public Fragment getItem(int position) {
            return InventoryDetailFragment.newInstance(position);
        }
    }

2.) I have a method that is trying to figure out the size of the image that needs to be downloaded without placing it in memory. Then compresses the image while downloading it to the required size. This is not successfully implemented. But I’m not sure what is going wrong.

private Bitmap downloadBitmap(String url, int width, int height) {
    Bitmap bitmap = null;
    int scale = 1;
    try {
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;  
        bitmap = BitmapFactory.decodeStream((InputStream)new URL (url).getContent(), null, options);

        if (options.outHeight > height || options.outWidth > width) {
            scale = (int) Math.max(((options.outHeight)/ height), ((options.outWidth)/ width));             }

        BitmapFactory.Options o2 = new BitmapFactory.Options();
        o2.inSampleSize = scale;
        bitmap = BitmapFactory.decodeStream((InputStream)new URL (url).getContent(), null, o2); 
        cache.put(url, new SoftReference<Bitmap>(bitmap));


    } catch (MalformedURLException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (Error e){
        Log.d("TEST", "Garbage Collector called!");
        System.gc();
    }
    return bitmap;
}

I have tried everything that I know how to do but it’s beyond my meager grasp of Android/Java. Please help! Thanks!

Answer 1

There are a few things that you need to change:

1. This is a horrible idea: BitmapFactory.decodeStream((InputStream)new URL (url).getContent(), null, options); You’re getting the image from the web each time this is executed (so twice in the code you posted). Instead, you need to download the image and cache it locally.

2. Add logic to your fragments to call recycle() on the bitmaps as soon as the fragment is detached. Add logic to always reload the image (from the cache) whenever the fragment is attached.

3. Lastly, your inSampleSize calculation is wrong. inSampleSize should be a value that’s a power of two, e.g. 1,2,4,8. You can use logarithms or simple binary logic to get the right one, this is what I use, which will always downsample using at least 2 (only call this if you know that the image is too big):

–

int ratio =  (int) Math.max((height/options.outHeight), ( width/options.outWidth); //notice that they're flipped     
  for (int powerOfTwo = 64; powerOfTwo >=2; powerOfTwo = powerOfTwo >> 1 ) { //find the biggest power of two that represents the ratio
    if ((ratio & powerOfTwo) > 0) {
      return powerOfTwo;
    }
  }