I solved with custom code. I added a button for each category that has a vendor with the same name of the category.
This is the code of the view
HikaShop - category / listing_img_title.php:
Code:
<?php
// Get a db connection.
$db = JFactory::getDbo();
// Create a new query object.
$query = $db->getQuery(true);
$query->select('vendor_id');
$query->from($db->quoteName('tbuonapp_hikamarket_vendor'));
$query->where('vendor_name = ' . '"' . $this->row->category_name . '"');
// Reset the query using our newly populated query object.
$db->setQuery($query);
$idVendor = $db->loadResult();
// Get a db connection.
$db = JFactory::getDbo();
// Create a new query object.
$query = $db->getQuery(true);
$query->select('vendor_alias');
$query->from($db->quoteName('tbuonapp_hikamarket_vendor'));
$query->where('vendor_name = ' . '"' . $this->row->category_name . '"');
// Reset the query using our newly populated query object.
$db->setQuery($query);
$aliasVendor = $db->loadResult();
?>
<?php if($idVendor != null and $idVendor != ""){ ?>
<br><br>
<div>
<a class ='hikabtn hikawishlist' href='<?php echo "https://www.buonapp.ch/voti-ristoranti/vendor/show/" . $idVendor . "-" . $aliasVendor; ?>'><span>Vota ristorante</span></a>
</div>
<?php } ?>
