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package java.awt.dnd;
import java.util.EventListener;
import java.awt.dnd.DropTargetDragEvent;
import java.awt.dnd.DropTargetDropEvent;
The DropTargetListener
interface
is the callback interface used by the
DropTarget
class to provide
notification of DnD operations that involve
the subject DropTarget
. Methods of
this interface may be implemented to provide
"drag under" visual feedback to the user throughout
the Drag and Drop operation.
Create a listener object by implementing the interface 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.
Since: 1.2
/**
* The <code>DropTargetListener</code> interface
* is the callback interface used by the
* <code>DropTarget</code> class to provide
* notification of DnD operations that involve
* the subject <code>DropTarget</code>. Methods of
* this interface may be implemented to provide
* "drag under" visual feedback to the user throughout
* the Drag and Drop operation.
* <p>
* Create a listener object by implementing the interface and then register it
* with a <code>DropTarget</code>. When the drag enters, moves over, or exits
* the operable part of the drop site for that <code>DropTarget</code>, when
* the drop action changes, and when the drop occurs, the relevant method in
* the listener object is invoked, and the <code>DropTargetEvent</code> is
* passed to it.
* <p>
* The operable part of the drop site for the <code>DropTarget</code> is
* the part of the associated <code>Component</code>'s geometry that is not
* obscured by an overlapping top-level window or by another
* <code>Component</code> higher in the Z-order that has an associated active
* <code>DropTarget</code>.
* <p>
* During the drag, the data associated with the current drag operation can be
* retrieved by calling <code>getTransferable()</code> on
* <code>DropTargetDragEvent</code> instances passed to the listener's
* methods.
* <p>
* Note that <code>getTransferable()</code> on the
* <code>DropTargetDragEvent</code> instance should only be called within the
* respective listener's method and all the necessary data should be retrieved
* from the returned <code>Transferable</code> before that method returns.
*
* @since 1.2
*/
public interface DropTargetListener extends EventListener {
Called while a drag operation is ongoing, when the mouse pointer enters
the operable part of the drop site for the DropTarget
registered with this listener.
Params: - dtde – the
DropTargetDragEvent
/**
* Called while a drag operation is ongoing, when the mouse pointer enters
* the operable part of the drop site for the <code>DropTarget</code>
* registered with this listener.
*
* @param dtde the <code>DropTargetDragEvent</code>
*/
void dragEnter(DropTargetDragEvent dtde);
Called when a drag operation is ongoing, while the mouse pointer is still
over the operable part of the drop site for the DropTarget
registered with this listener.
Params: - dtde – the
DropTargetDragEvent
/**
* Called when a drag operation is ongoing, while the mouse pointer is still
* over the operable part of the drop site for the <code>DropTarget</code>
* registered with this listener.
*
* @param dtde the <code>DropTargetDragEvent</code>
*/
void dragOver(DropTargetDragEvent dtde);
Called if the user has modified
the current drop gesture.
Params: - dtde – the
DropTargetDragEvent
/**
* Called if the user has modified
* the current drop gesture.
* <P>
* @param dtde the <code>DropTargetDragEvent</code>
*/
void dropActionChanged(DropTargetDragEvent dtde);
Called while a drag operation is ongoing, when the mouse pointer has
exited the operable part of the drop site for the
DropTarget
registered with this listener.
Params: - dte – the
DropTargetEvent
/**
* Called while a drag operation is ongoing, when the mouse pointer has
* exited the operable part of the drop site for the
* <code>DropTarget</code> registered with this listener.
*
* @param dte the <code>DropTargetEvent</code>
*/
void dragExit(DropTargetEvent dte);
Called when the drag operation has terminated with a drop on
the operable part of the drop site for the DropTarget
registered with this listener.
This method is responsible for undertaking
the transfer of the data associated with the
gesture. The DropTargetDropEvent
provides a means to obtain a Transferable
object that represents the data object(s) to
be transfered.
From this method, the DropTargetListener
shall accept or reject the drop via the
acceptDrop(int dropAction) or rejectDrop() methods of the
DropTargetDropEvent
parameter.
Subsequent to acceptDrop(), but not before,
DropTargetDropEvent
's getTransferable()
method may be invoked, and data transfer may be
performed via the returned Transferable
's
getTransferData() method.
At the completion of a drop, an implementation
of this method is required to signal the success/failure
of the drop by passing an appropriate
boolean
to the DropTargetDropEvent
's
dropComplete(boolean success) method.
Note: The data transfer should be completed before the call to the
DropTargetDropEvent
's dropComplete(boolean success) method.
After that, a call to the getTransferData() method of the
Transferable
returned by
DropTargetDropEvent.getTransferable()
is guaranteed to
succeed only if the data transfer is local; that is, only if
DropTargetDropEvent.isLocalTransfer()
returns
true
. Otherwise, the behavior of the call is
implementation-dependent.
Params: - dtde – the
DropTargetDropEvent
/**
* Called when the drag operation has terminated with a drop on
* the operable part of the drop site for the <code>DropTarget</code>
* registered with this listener.
* <p>
* This method is responsible for undertaking
* the transfer of the data associated with the
* gesture. The <code>DropTargetDropEvent</code>
* provides a means to obtain a <code>Transferable</code>
* object that represents the data object(s) to
* be transfered.<P>
* From this method, the <code>DropTargetListener</code>
* shall accept or reject the drop via the
* acceptDrop(int dropAction) or rejectDrop() methods of the
* <code>DropTargetDropEvent</code> parameter.
* <P>
* Subsequent to acceptDrop(), but not before,
* <code>DropTargetDropEvent</code>'s getTransferable()
* method may be invoked, and data transfer may be
* performed via the returned <code>Transferable</code>'s
* getTransferData() method.
* <P>
* At the completion of a drop, an implementation
* of this method is required to signal the success/failure
* of the drop by passing an appropriate
* <code>boolean</code> to the <code>DropTargetDropEvent</code>'s
* dropComplete(boolean success) method.
* <P>
* Note: The data transfer should be completed before the call to the
* <code>DropTargetDropEvent</code>'s dropComplete(boolean success) method.
* After that, a call to the getTransferData() method of the
* <code>Transferable</code> returned by
* <code>DropTargetDropEvent.getTransferable()</code> is guaranteed to
* succeed only if the data transfer is local; that is, only if
* <code>DropTargetDropEvent.isLocalTransfer()</code> returns
* <code>true</code>. Otherwise, the behavior of the call is
* implementation-dependent.
* <P>
* @param dtde the <code>DropTargetDropEvent</code>
*/
void drop(DropTargetDropEvent dtde);
}