为什么数量不会随着magento 1.9.2中购物车页面的总价格而更新？

Question

I have used the follow code in checkout/cart page in my theme:
<?php foreach($this->getItems() as $_item): ?>
                   <hr>
              </hr> <?php echo $this->getItemHtml($_item) ?>

                <?php endforeach ?>

<?php echo $this->getMessagesBlock()->toHtml() ?>
    <?php echo $this->getChildHtml('form_before') ?>
     <form action="<?php echo $this->getUrl('checkout/cart/updatePost') ?>" method="post">

        <?php echo $this->getBlockHtml('formkey'); ?>
      <fieldset>
<input type="hidden" name="form_key" value="<?php echo Mage::getSingleton('core/session')->getFormKey(); ?>"/>

  <button type="submit" name="update_cart_action"  value="update_qty" title="<?php echo Mage::helper('core')->quoteEscape($this->__('Update Shopping Cart')); ?>" class="btnn4"><span><span><?php echo $this->__('Update Shopping Cart'); ?></span></span></button>

<script type="text/javascript">decorateTable('shopping-cart-table')</script>
        </fieldset> 
    </form>

checkout / cart / item / default.phtml与基地保持一致。当我在购物车页面中添加一些数量时..点击更新按钮后页面正在重新加载，但是数字的倍数值未显示并且数量保持不变。