Trouble with onSelect for Listbox on iphone

<div apply="org.zkoss.bind.BindComposer" viewModel="@id('vm') @init('forum.ListboxVM')">
<listbox model="@bind(vm.model)" itemRenderer="@bind(vm.renderer)" onSelect='alert("select event")'>
    <listhead>
        <listheader label="name"></listheader>
    </listhead>
</listbox>
</div>

public class ListboxVM {

	private List<Item> list;
	private ListModelList<Item> listModel;
	private ListitemRenderer<Item> itemRenderer;
	
	public ListModelList<Item> getModel() {
		if(listModel== null) {
			listModel= new ListModelList<Item>(getAllItems());
		}
		return listModel;
	}
	
	public ListitemRenderer<Item> getRenderer() {
		if (itemRenderer == null) {
			itemRenderer = new ListitemRenderer<Item>() {
				@Override
				public void render(Listitem litem, Item item, int index) throws Exception {
					new Listcell(item.getName()).setParent(litem);
				}
			};
		}
		return itemRenderer;
	}
	
	private List<Item> getAllItems() {
		list= new ArrayList<Item>();
		list.add(new Item("David"));
		list.add(new Item("Tom"));
		list.add(new Item("Tim"));
		return list;
	}
	
	public class Item {
		private String name;
		public Item(String name) {
			this.name = name;
		}
		public String getName() { return name; }
		public void setName(String name) { this.name = name; }
	}
}