gistfile1.java

public class UpdateAdapter extends ArrayAdapter<ParseObject> {
  // omitted vars
  public List<ParseObject> updates = new ArrayList<ParseObject>();
	public HashMap<String, Bitmap> updateImages = new HashMap<String, Bitmap>();
	
  // omitted constructor + @Overrides
	
		@Override
	public View getView(int position, View convertView, ViewGroup parent) {			
		UpdateHolder holder = null;
		
		if (convertView == null) {
			// omitted inflater setup
      
			holder = new UpdateHolder();
			holder.imageView = (ImageView) convertView.findViewById(R.id.update_image);
			convertView.setTag(holder);
		}
		else {
			holder = (UpdateHolder) convertView.getTag();
		}
		
		ParseObject update = updates.get(position);
		ParseFile imageData = (ParseFile) update.get(Update.IMAGE_KEY);
		if (imageData != null && holder.imageView.getTag() == null) {
			Bitmap bmp = updateImages.get(imageData.getUrl());
			if (bmp != null) {
				holder.imageView.setImageBitmap(bmp);
			}
			else {
				holder.imageView.setImageResource(R.drawable.placeholder_square);
				holder.imageView.setTag(this);
				loadImage(imageData, holder.imageView);
			}
		}
		
		return convertView;
	}
	
	void loadImage(final ParseFile parseFile, final ImageView imageView) {
		parseFile.getDataInBackground(new GetDataCallback() {
			
			@Override
			public void done(byte[] data, ParseException e) {
				if(imageView.getTag() != null && data != null) {
					InputStream is = new ByteArrayInputStream(data);
					Bitmap bmp = BitmapFactory.decodeStream(is);
					imageView.setImageBitmap(bmp);
					updateImages.put(parseFile.getUrl(), bmp);
				}
				
				imageView.setTag(null);
			}
		});
	}
	
	public class UpdateHolder {
    // omitted view vars
		ImageView imageView;
	}
}