Magento, add and set a checkbox on grid and form backend

Question

I've a fully working backend page with a grid and a corresponding form to edit the changes on the corresponding model. I added a new field on the table, bit type, as it will answer to a yes/no configuration option from the user. I added the checkbox on both grid and form.

My problem is that after a couple of hours of searching and trying different approaches I can not set the checkbox checked value both on the grid and the form reading the corresponding field from the database. Also when I click on save on the form the value corresponding to the checkbox is always saved with 1. Everything else on the grid and the form works as it should. I have read here, here, here, here and some more sites and SO questions/answers but still no clue on what I'm doing wrong. Some solutions recommend using a combo box with YES/NO options, but I want a checkbox, can't be so difficult.

Grid code inside the function _prepareColumns():

protected function _prepareColumns() {
    ...
    $this->addColumn('banner_gral', array(
        'header'    => Mage::helper('banners')->__('General'),
        'align'     => 'center',
        'index'     => 'banner_gral',
        'type'      => 'checkbox',
        'values'    => $this->getBannerGral()==1 ? 'true' : 'false',
     ));
    ...
}

public function __construct()
{
    parent::__construct();
    $this->setId('bannersgrid');
    $this->setDefaultSort('bannerid');
    $this->setDefaultDir('asc');
    $this->setSaveParametersInSession(true);
    $this->setUseAjax(true);
}

public function getGridUrl()
{
    return $this->getUrl('*/*/grid', array('_current'=>true));
}

protected function _prepareCollection()
{
    $collection = Mage::getModel('banners/bannersadmin')->getCollection();
    $this->setCollection($collection);
    return parent::_prepareCollection();
}

Form code to add the checkbox inside the function _prepareForm():

protected function _prepareForm()
{
    $id = $this->getRequest()->getParam('id');
    $params = array('id' => $this->getRequest()->getParam('id'));

    if (Mage::registry('banners_data')->getdata())  {
        $data = Mage::registry('banners_data')->getdata();
    }
    elseif (Mage::getSingleton('adminhtml/session')) {
        $data = Mage::getSingleton('adminhtml/session')->getdata();
        Mage::getSingleton('adminhtml/session')->getdata(null);
    }
    else {
        $data = array();
    }

    $form = new Varien_Data_Form(array(
                                    'id' => 'edit_form',
                                    'action' => $this->getUrl('*/*/save', $params),
                                    'method' => 'post',
                                    'enctype' => 'multipart/form-data',
    ));
    ...

    $fieldset->addField('banner_gral', 'checkbox', array(
        'label'    => Mage::helper('banners')->__('Is general'),
        'name'     => 'banner_gral',
        'class'    => 'banner_gral',
        'checked'  => $this->getBannerGral()==1 ? 'true' : 'false',
        'onclick'  => 'this.value == this.checked ? 1 : 0',
        'note'     => Mage::helper('banners')->__('blablablabla'),
        'tabindex'  => 2
    ));
    ...
}

On the saveAction() of my form I have:

$campaign->setbanner_gral(!empty($data['banner_gral']));

Answer 1

In your controller saveAction() when saving the checkbox data do

$banner_gral = isset($your_form_Data['banner_gral']) ? 1 : 0;

For Grid and Form Page

In your controller you should have Mage::register(...)->getData() or Mage::register(...)

public function editAction()
     ....
     Mage::register('example_data', $model);

On your form _prepareForm()

$model = Mage::registry('example_data'); // NOTE registry('example_data'); NOT registry('example_data')->getData();

$fieldset->addField('entire_range', 'checkbox', array(
      ....
      'checked'    => $model->getBannerGral()==1 ? 'true' : 'false',
       ......
))

see http://www.magentocommerce.com/boards/viewthread/20536/

On your grid _prepareColumns()

$this->addColumn('banner_gral', array(
    ....
    'type'     => 'checkbox',
    'index'    => 'banner_gral',
    'values'   => array(1,2),
    'field_name' => 'checkbox_name',
    ....
));