https://openjdk.java.net/ 
/*
 * Copyright (c) 1997, 2007, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

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} interface
 * is the callback interface used by the
 * {@code DropTarget} class to provide
 * notification of DnD operations that involve
 * the subject {@code DropTarget}. 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}. When the drag enters, moves over, or exits
 * the operable part of the drop site for that {@code DropTarget}, when
 * the drop action changes, and when the drop occurs, the relevant method in
 * the listener object is invoked, and the {@code DropTargetEvent} is
 * passed to it.
 * <p>
 * The operable part of the drop site for the {@code DropTarget} is
 * the part of the associated {@code Component}'s geometry that is not
 * obscured by an overlapping top-level window or by another
 * {@code Component} higher in the Z-order that has an associated active
 * {@code DropTarget}.
 * <p>
 * During the drag, the data associated with the current drag operation can be
 * retrieved by calling {@code getTransferable()} on
 * {@code DropTargetDragEvent} instances passed to the listener's
 * methods.
 * <p>
 * Note that {@code getTransferable()} on the
 * {@code DropTargetDragEvent} instance should only be called within the
 * respective listener's method and all the necessary data should be retrieved
 * from the returned {@code Transferable} 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}
     * registered with this listener.
     *
     * @param dtde the {@code DropTargetDragEvent}
     */

    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}
     * registered with this listener.
     *
     * @param dtde the {@code DropTargetDragEvent}
     */

    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.
     *
     * @param dtde the {@code DropTargetDragEvent}
     */

    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} registered with this listener.
     *
     * @param dte the {@code DropTargetEvent}
     */

    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 transferred.
 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}
     * registered with this listener.
     * <p>
     * This method is responsible for undertaking
     * the transfer of the data associated with the
     * gesture. The {@code DropTargetDropEvent}
     * provides a means to obtain a {@code Transferable}
     * object that represents the data object(s) to
     * be transferred.<P>
     * From this method, the {@code DropTargetListener}
     * shall accept or reject the drop via the
     * acceptDrop(int dropAction) or rejectDrop() methods of the
     * {@code DropTargetDropEvent} parameter.
     * <P>
     * Subsequent to acceptDrop(), but not before,
     * {@code DropTargetDropEvent}'s getTransferable()
     * method may be invoked, and data transfer may be
     * performed via the returned {@code Transferable}'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} to the {@code DropTargetDropEvent}'s
     * dropComplete(boolean success) method.
     * <P>
     * Note: The data transfer should be completed before the call  to the
     * {@code DropTargetDropEvent}'s dropComplete(boolean success) method.
     * After that, a call to the getTransferData() method of the
     * {@code Transferable} returned by
     * {@code DropTargetDropEvent.getTransferable()} is guaranteed to
     * succeed only if the data transfer is local; that is, only if
     * {@code DropTargetDropEvent.isLocalTransfer()} returns
     * {@code true}. Otherwise, the behavior of the call is
     * implementation-dependent.
     *
     * @param dtde the {@code DropTargetDropEvent}
     */

    void drop(DropTargetDropEvent dtde);
}