| An abstract adapter class for receiving drop target events. The methods in
this class are empty. This class exists only as a convenience for creating
listener objects.
Extend this class to create a DropTargetEvent listener
and override the methods for the events of interest. (If you implement the
DropTargetListener interface, you have to define all of
the methods in it. This abstract class defines a null implementation for
every method except drop(DropTargetDropEvent), so you only have
to define methods for events you care about.) You must provide an
implementation for at least drop(DropTargetDropEvent). This
method cannot have a null implementation because its specification requires
that you either accept or reject the drop, and, if accepted, indicate
whether the drop was successful.
Create a listener object using the extended class and then register it with
a DropTarget. When the drag enters, moves over, or exits
the operable part of the drop site for that DropTarget, when
the drop action changes, and when the drop occurs, the relevant method in
the listener object is invoked, and the DropTargetEvent is
passed to it.
The operable part of the drop site for the DropTarget is
the part of the associated Component's geometry that is not
obscured by an overlapping top-level window or by another
Component higher in the Z-order that has an associated active
DropTarget.
During the drag, the data associated with the current drag operation can be
retrieved by calling getTransferable() on
DropTargetDragEvent instances passed to the listener's
methods.
Note that getTransferable() on the
DropTargetDragEvent instance should only be called within the
respective listener's method and all the necessary data should be retrieved
from the returned Transferable before that method returns. | 