public class ViewportChangeNotifier
extends java.lang.Object
It is sometimes useful to know if a component has changed its position on
screen as a result of scrolling. The component might not be added directly
to the scrolled viewport or it might be part of a component hierarchy that
contains many viewports. This class finds all of the viewports in a
components hierarchy and listens for position changes to them, forwarding their
events to interested ChangeListeners.
To use, create an instance of this class with the component to monitor. The
instance will begin listening to the viewports in the component hierarchy
immediately or whenever the component is first added to the hierarchy.
If the component hierarchy changes at any parent level then this mechanism
reassociates automatically with any new or removed viewports.
When done, dispose() must be called or the references to the viewports and the
component may be retained causing a memory leak.