after releasing the long click, the item is getting deselected automatically.
holder.attach_img.setOnLongClickListener(new View.OnLongClickListener() {
@Override
public boolean onLongClick(View v) {
if (lvChatList.isItemChecked(position))
lvChatList.setItemChecked(position, false);
else
lvChatList.setItemChecked(position, true);
notifyDataSetChanged();
return false;
}
});