Try the following:
add to __construct:
add_action('admin_bar_menu', array( &$this, 'add_toolbar_wcmenucart' ), 100);
then add the function:
public function add_toolbar_wcmenucart($admin_bar){
if (!is_admin()) {
$dom = new DOMDocument();
$dom->loadHTML($this->wcmenucart_menu_item());
foreach ($dom->getElementsByTagName('a') as $a) {
$menutitle = $a->nodeValue;
$menuhref = $a->getAttribute('href');
}
$admin_bar->add_menu( array(
'id' => 'wcmenucart',
'title' => '<i class="wcmenucart-icon-shopping-cart-0"></i>'.$menutitle,
'href' => $menuhref,
'meta' => array(
'title' => __('View your shopping cart', 'wcmenucart'),
),
));
}
}
should work