Question

I am building a book viewer for Android 3.0 Honeycomb. It has been working fine on the Samsung Galaxy Tab but gets a lot of OutOfMemoryErrors on the Motorola Xoom on 3.0.1. Both devices have 48MB VM heap space.

I have 2 activities:

BookActivity – has a SlowGallery which loads 1280×640 images and a small Gallery which loads 160×80 images.

The SlowGallery is a minor override to make it fling one gallery item at a time instead of scrolling quickly.

BitmapActivity – has a single ImageView which loads an 4488×2244 image and a small Gallery which loads 160×80 images. Reducing the size of the image is not an option because the user is intended to enlarge the image to 100%.

I put this in the Bitmap-loading method to reduce the bitmap to 16-bit:

BitmapFactory.Options o2 = new BitmapFactory.Options();
if (compressColor) o2.inPreferredConfig = Bitmap.Config.RGB_565;
o2.inPurgeable = true;
o2.inInputShareable = true;
o2.inSampleSize = (int) scale;
b = BitmapFactory.decodeStream(fis, null, o2);

When I double-tap the BookActivity’s Gallery, it calls BitmapActivity, passing the respective image number to be opened. I can do this 1-3 times, entering the BitmapActivity, then clicking Back, before it hits an OutOfMemoryError.

On double-tapping the Gallery it calls PageAdapter.purge(), which appears to visually unload the gallery’s images.

This is BookActivity.PageAdapter, which is the adapter for the SlowGallery:

private class PageAdapter extends BaseAdapter {
private final LayoutInflater mInflater;
private Page currentPage;
private boolean purge = false;
private WeakReference<Bitmap> weakReferenceBitmap;
public PageAdapter(Context context) {
    mInflater = LayoutInflater.from(context);
}
public void unpurge() {
    purge = false;
    notifyDataSetChanged();
}   
public void purge() {
    purge = true;
    holder = null;
    notifyDataSetChanged();
}       
@Override
public int getCount() {
    if (listPages==null || purge) return 0;
    return listPages.size();
}
@Override
public Object getItem(int position) {
    return null;
}
@Override
public long getItemId(int position) {
    return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
    if (convertView == null) {
        convertView = mInflater.inflate(R.layout.gallery_pages, null);
        holder = new ViewHolderIssues();
        holder.image = (ImageView) convertView.findViewById(R.id.ImageViewPage);
        convertView.setTag(holder);
    } else {
        holder = (ViewHolderIssues) convertView.getTag();
    }
    if (position < listPages.size()) {
        currentPage = listPages.get(position);
        File f = new File(Engine.PATH + currentPage.getImageMedium());
        if (!purge) {
            if (!f.exists()) {
                holder.image.setImageResource(R.drawable.loading);
                Engine.triggerTrickle(currentPage.getImageMedium(), WeightedAsset.IMAGE_MEDIUM, getApplicationContext());                   
            } else {
                weakReferenceBitmap = new WeakReference<Bitmap>(Engine.loadImageFromBitmap(currentPage.getImageMedium(), screenWidth, 1, true));
                if (weakReferenceBitmap.get()!=null) {
                    holder.image.setImageBitmap(weakReferenceBitmap.get());
                } else {
                    holder.image.setImageDrawable(null);
                }
            }
        } else {
            weakReferenceBitmap.clear();
            holder.image.setImageDrawable(null);
            holder = null;
            System.gc();
        }
        f = null;
    }
    return convertView;
}
}

Looking at the HPROF file, under the Dominator Tree, it appears that the BookActivity.SlowGallery still exists even when I am in BitmapActivity. When in BookActivity, SlowGallery takes up 3.2-6.5MB (1.6MB per image) but in BitmapActivity it takes up 1.6MB (SlowGallery.LinearLayout.ImageView.BitmapDrawable = 1.6MB). How do I get rid of SlowGallery?

Answer 1

Ah, kinda complex chunk of code there. The weak references may help, but in general, if using an ImageView in an adapter, before you set the new bitmap you should fetch the old Bitmap and then call Bitmap.recycle(). You should also do that your BitmapActivity when it is destroyed. That should do most of what you need.