@Override
 public void setImageBitmap(Bitmap bm) {
   currentBitmap = bm;
   super.setImageBitmap(currentBitmap);
   if (imageChangeListener != null) imageChangeListener.changed((currentBitmap == null));
 }
 @Override
 public void setImageDrawable(Drawable d) {
   super.setImageDrawable(d);
   if (imageChangeListener != null) imageChangeListener.changed((d == null));
 }
 @Override
 public void setImageBitmap(Bitmap bm) {
   super.setImageBitmap(bm);
   if (imageChangeListener != null) imageChangeListener.changed((bm == null));
 }