How to make a Button displaying a drop down list using GWT?

I'm trying to using GWT 2.4 to make a widget just like below: a button, when clicking it can show a drop-down list under it. This picture is from Google's new Blogger system.

Anyone could shed some light on this?

enter image description here

Solution

You could use a MenuBar widget with a single menu item (being the button) having a submenu (the dropdown menu).

Or you could use a Button, and from within a ClickHandler you'd show a PopupPanel containing a vertical MenuBar relative to the button (which you'd set as an auto-hide partner)