Button redirecting to the grid page

Question

I have a custom module 'banner' and in which I have added a button in its second tab(only two tabs for the module). when click on that button, it is submitting my banner automatically and then go to the grid page(i e it acts as just another save button). But the function of this button is to add an uploading image field.ie whenever the button is clicked, it should add an image form field to my tab file. This is my tab file.

<?php
    class Karaokeshop_Banner_Block_Adminhtml_Banner_Edit_Tab_Image extends Mage_Adminhtml_Block_Widget_Form
    {

        protected function _prepareForm()
        {
            $form = new Varien_Data_Form();
            $this->setForm($form);
            $fieldset = $form->addFieldset('banner_image', array('legend'=>Mage::helper('banner')->__('Banner Image')));
            //declaring a new custom form field and adding
            $fieldset->addType('add_button', 'Karaokeshop_Banner_Block_Adminhtml_Banner_Edit_Tab_Field_Custom'); 
            $fieldset->addField('banner_img_add_button', 'add_button', array(
                'title' => Mage::helper('banner')->__('Add Banner Image'),
                'id' => 'add_banner_img_button',
                'class' => 'scalable save',
                'style' => '',
                'onclick' => 'banner.add(this)',
                'type' => 'button',                    
            ));

             return parent::_prepareForm();                                                    
        }  

}  

this is my button defining file

<?php
    class Karaokeshop_Banner_Block_Adminhtml_Banner_Edit_Tab_Field_Custom extends Varien_Data_Form_Element_Abstract
    {
public function __construct($attributes=array())
{
    parent::__construct($attributes);
}
public function getElementHtml()
{              
    $value = $this->getTitle();
    $onclick=$this->getOnclick();
    $class=$this->getClass();
    $id=$this->getId();
    $style=$this->getStyle();
    $type=$this->getType();
    $html='<button id="'.$id.'" class="'.$class.'" style="'.$style.'" onclick="'.$onclick.'" type="'.$type.'" title="'.$value.'">'.$value.' </button>';
    $html .= '<p id="' . $this->getHtmlId() . '"'. $this->serialize($this->getHtmlAttributes()) .'>
                <script type="text/javascript">
                //<![CDATA[

                    var banner =  
                    {                                                       
                            add : function(obj) 
                            {                                    

                            },

                    };
                //]]>
                </script>
            </p>';
    return $html;
}
}

what should i do to change my button to an add button? what should I do to avoid this submitting functionality of the button. Please help me. Thanks in advance

Answer 1

I got the answer for this. That was a small javascript error. I just need to add retun false; in my banner.add() function. It will prevent submitting the form and hence stay in the same page