Android สอบถามเรื่อง listview เกี่ยวกับ position ครับ เรื่องการเลือก

BHArrayAdapter<PackagePeriodDetailInfo> adapter = new BHArrayAdapter<PackagePeriodDetailInfo>(
							activity, R.layout.list_detailcheck,
							packagepreioddetailinfo) {
						class ViewHolder {
							public TextView textViewNumber, textViewPay;
						}

						@Override
						protected void onViewItem(int position, View view,
								Object holder, PackagePeriodDetailInfo info) {
							// TODO Auto-generated method stub
							ViewHolder vh = (ViewHolder) holder;

					//		float price = getItem(0).PaymentAmount;
					//		float discount = CONTRACT.TradeInDiscount;
					//		float sum = price - discount;

							vh.textViewNumber.setText(""+ info.PaymentPeriodNumber);
							vh.textViewPay.setText(BHUtilities.numericFormat(info.PaymentAmount));
							
							
					//		PAYMENT_FIRST = getItem(0).PaymentAmount;
					//		PAYMENT_SECOND = getItem(1).PaymentAmount;

						}
					};
					listViewInstallment.setAdapter(adapter);