Titanium.UI.ButtonBar.add

There are certain top-level containers that are not intended to be added as the children of other views. These top-level containers include Window, SplitWindow, and TabGroup. Other types of views must be added to a top-level container in order to be displayed on screen.

The special containers NavigationGroup, SplitWindow, Tab, and TabGroup manage windows. These managed windows may be referred to as children of the container, but they are not added using the add method.

Note that although a NavigationGroup manages windows, it is not itself top-level container. It must be added to a Window in order to be displayed.

Tab is another kind of special container: it is not itself a top-level container, but can only be used within a TabGroup. You cannot add a Tab to an arbitrary container.