The DragHandler Interface contains the following methods:
dragEnter notifies the recipient when a source object enters the space that is defined by a container, window, or object.
dragLeave notifies the recipient when a source object exits the space that is defined by a container, window, or object.
dragOver notifies the recipient when a source object continues through the space that is defined by a container, window, or object.
drop notifies the recipient when a source object is dropped at a new location.