Android控制自定义列表视图中的按钮

@Override
public View getView(final int position, View convertView, ViewGroup parent) {
    // TODO Auto-generated method stub
    Holder holder=new Holder();
    View rowView;
    rowView = inflater.inflate(R.layout.receiptlistsample, null);
    holder.product=(TextView) rowView.findViewById(R.id.product);
    holder.quantity=(TextView) rowView.findViewById(R.id.quan);
    holder.price=(TextView) rowView.findViewById(R.id.price);
    holder.add = (ImageButton)rowView.findViewById(R.id.plus);
    holder.cancel = (ImageButton)rowView.findViewById(R.id.minus);
    holder.product.setText(pro[position]);
    holder.quantity.setText(quant[position]);
    holder.price.setText(pri[position]);
    holder.add.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View view) {
               Toast.makeText(context, "add ", Toast.LENGTH_LONG).show();
        }
    });
    holder.cancel.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View view) {
            Toast.makeText(context, "cancel ", Toast.LENGTH_LONG).show();
        }
    });

    return rowView;
}}
@Override
public View getView(final int positio