In an earlier recipe from this chapter, we stated why combos are generally better than checkboxes when we need to provide the user with an elaborate list of items to choose from. Well, the only drawback to that assertion is that while checkboxes are designed to allow multiple selections, the GXT ComboBox isn't, at least not without some sort of plugin. Thankfully, there are two ways (excluding the plugin approach) to solve this in GXT, the first is to use a ListField and the second is the DualListField, both of which provide multiple selections out-of-the-box.
ListField behaves like HTML SELECT element having the multiple attribute turned on, thus it allows the user to make multiple selections while holding the Ctrl (control) or Shift key. DualListField on the other hand is an implantation of GXT's MultiField, combining two ListField objects into one widget and allowing the user to select from one (source list) into the other (destination list) easily...