/* * Copyright (c) 2001, 2003, 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; /** * 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. * <p> * Extend this class to create a <code>DropTargetEvent</code> listener * and override the methods for the events of interest. (If you implement the * <code>DropTargetListener</code> interface, you have to define all of * the methods in it. This abstract class defines a null implementation for * every method except <code>drop(DropTargetDropEvent)</code>, so you only have * to define methods for events you care about.) You must provide an * implementation for at least <code>drop(DropTargetDropEvent)</code>. 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. * <p> * Create a listener object using the extended class 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. * * @see DropTargetEvent * @see DropTargetListener * * @author David Mendenhall * @since 1.4 */public abstract class DropTargetAdapter implements DropTargetListener {     /**     * 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>     */    public 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 <code>DropTarget</code>     * registered with this listener.     *     * @param dtde the <code>DropTargetDragEvent</code>     */    public void dragOver(DropTargetDragEvent dtde) {}     /**     * Called if the user has modified     * the current drop gesture.     *     * @param dtde the <code>DropTargetDragEvent</code>     */    public 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     * <code>DropTarget</code> registered with this listener.     *     * @param dte the <code>DropTargetEvent</code>     */    public void dragExit(DropTargetEvent dte) {}}