Checkbox showing multiple time in grid view holder Pattern

i am showing and hiding checkbox on imageview click in gridview but when i click on one imageView checkbox appear on multiple image view android and as i scroll visible checkbox goes missing when i scroll here is my Adapter

     public class ImageAdapter extends BaseAdapter {
        private LayoutInflater mInflater;

        public ImageAdapter() {
            mInflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        }



        public int getCount() {
            return arrPath.length;
        }

        public Object getItem(int position) {
            return position;
        }

        public long getItemId(int position) {
            return position;
        }

        public View getView(final int position, View convertView, ViewGroup parent) {
            final ViewHolder holder;
            if (convertView == null) {
                holder = new ViewHolder();
                convertView = mInflater.inflate(
                        R.layout.galleryitems, parent,false);
                holder.imageview = (ImageView) convertView.findViewById(R.id.thumbImage);
                holder.checkbox = (CheckBox) convertView.findViewById(R.id.itemCheckBox);
                convertView.setTag(R.id.itemCheckBox, holder.checkbox);
                convertView.setTag(R.id.thumbImage,holder.imageview);
                convertView.setTag(holder);




            } else {
                holder = (ViewHolder) convertView.getTag();
                holder.checkbox = (CheckBox)convertView.getTag();
                holder.imageview = (ImageView)convertView.getTag();
            }
            holder.checkbox.setId(position);
            holder.imageview.setId(position);
            holder.checkbox.setOnClickListener(new View.OnClickListener() {
                public void onClick(View v) {
                    // TODO Auto-generated method stub
                    CheckBox cb = (CheckBox) v;
                    int id = cb.getId();


                    if (thumbnailsselection[id]) {
                        cb.setChecked(false);
                        thumbnailsselection[id] = false;
                    } else {
                        cb.setChecked(true);
                        thumbnailsselection[id] = true;
                    }
                }
            });
            holder.imageview.setOnClickListener(new View.OnClickListener() {

                public void onClick(View v) {
                    // TODO Auto-generated method stub
                    ImageView iv = (ImageView )v;
                    int id = iv.getId();
                    if (holder.checkbox.getVisibility() == View.GONE) {

                            holder.checkbox.getTag();
                            holder.imageview.getTag();
                            holder.imageview.setAlpha(0.22f);
                            holder.checkbox.setVisibility(View.VISIBLE);
                            holder.checkbox.setChecked(true);


                    } else if (holder.checkbox.getVisibility() == View.VISIBLE) {
                        holder.imageview.setAlpha(0.8f);
                        holder.checkbox.setVisibility(View.GONE);
                    }



                }
            });
            holder.checkbox.setTag(position);
            holder.imageview.setImageBitmap(thumbnails[position]);
            holder.checkbox.setChecked(thumbnailsselection[position]);
            holder.id = position;
            return convertView;
        }
 }

    class ViewHolder {
        ImageView imageview;
        CheckBox checkbox;
        int id;
    }
}