Add total in magento custom module grid footer - magento

Question

i have added sales order grid in my custom module.and also get footer total row in the grid. but the problem is when i add 'adult' column in the total it display nothing.for adult,child,total i m using renderer to get row data from order.so how to get total for adult,child,total at the footer.
i have used below code to display footer totals in grid.php
protected $_countTotals = true;
public function getTotals()
{
$totals = new Varien_Object();
$fields = array(
'base_grand_total' => 0,
'adult'=>0,
//actual column index, see _prepareColumns()
);
foreach ($this->getCollection() as $item) {
foreach($fields as $field=>$value){
$fields[$field]+=$item->getData($field);
}
}
//First column in the grid
$fields['increment_id'] = 'Totals';
$totals->setData($fields);
return $totals;
}
Thanks

Answer 1

Add this function to the grid.php
public function getReport($from, $to) {
if ($from == '') {
$from = $this->getFilter('report_from');
}
if ($to == '') {
$to = $this->getFilter('report_to');
}
$totalObj = Mage::getModel('reports/totals');
$totals = $totalObj->countTotals($this, $from, $to);
$this->setTotals($totals);
$this->addGrandTotals($totals);
return $this->getCollection()->getReport($from, $to);
}
and also in adding column add 'total' => 'sum' as below (I think you made this but once verify it properly):
$this->addColumn('item_id', array(
'header' => Mage::helper('mymodule')->__('Item ID'),
'align' => 'right',
'index' => 'item_id',
'type' => 'number',
'total' => 'sum',
));