1/*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
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24 */
25
26package java.awt.dnd;
27
28/**
29 * An abstract adapter class for receiving drop target events. The methods in
30 * this class are empty. This class exists only as a convenience for creating
31 * listener objects.
32 * <p>
33 * Extend this class to create a {@code DropTargetEvent} listener
34 * and override the methods for the events of interest. (If you implement the
35 * {@code DropTargetListener} interface, you have to define all of
36 * the methods in it. This abstract class defines a null implementation for
37 * every method except {@code drop(DropTargetDropEvent)}, so you only have
38 * to define methods for events you care about.) You must provide an
39 * implementation for at least {@code drop(DropTargetDropEvent)}. This
40 * method cannot have a null implementation because its specification requires
41 * that you either accept or reject the drop, and, if accepted, indicate
42 * whether the drop was successful.
43 * <p>
44 * Create a listener object using the extended class and then register it with
45 * a {@code DropTarget}. When the drag enters, moves over, or exits
46 * the operable part of the drop site for that {@code DropTarget}, when
47 * the drop action changes, and when the drop occurs, the relevant method in
48 * the listener object is invoked, and the {@code DropTargetEvent} is
49 * passed to it.
50 * <p>
51 * The operable part of the drop site for the {@code DropTarget} is
52 * the part of the associated {@code Component}'s geometry that is not
53 * obscured by an overlapping top-level window or by another
54 * {@code Component} higher in the Z-order that has an associated active
55 * {@code DropTarget}.
56 * <p>
57 * During the drag, the data associated with the current drag operation can be
58 * retrieved by calling {@code getTransferable()} on
59 * {@code DropTargetDragEvent} instances passed to the listener's
60 * methods.
61 * <p>
62 * Note that {@code getTransferable()} on the
63 * {@code DropTargetDragEvent} instance should only be called within the
64 * respective listener's method and all the necessary data should be retrieved
65 * from the returned {@code Transferable} before that method returns.
66 *
67 * @see DropTargetEvent
68 * @see DropTargetListener
69 *
70 * @author David Mendenhall
71 * @since 1.4
72 */
73public abstract class DropTargetAdapter implements DropTargetListener {
74
75    /**
76     * Called while a drag operation is ongoing, when the mouse pointer enters
77     * the operable part of the drop site for the {@code DropTarget}
78     * registered with this listener.
79     *
80     * @param dtde the {@code DropTargetDragEvent}
81     */
82    public void dragEnter(DropTargetDragEvent dtde) {}
83
84    /**
85     * Called when a drag operation is ongoing, while the mouse pointer is still
86     * over the operable part of the drop site for the {@code DropTarget}
87     * registered with this listener.
88     *
89     * @param dtde the {@code DropTargetDragEvent}
90     */
91    public void dragOver(DropTargetDragEvent dtde) {}
92
93    /**
94     * Called if the user has modified
95     * the current drop gesture.
96     *
97     * @param dtde the {@code DropTargetDragEvent}
98     */
99    public void dropActionChanged(DropTargetDragEvent dtde) {}
100
101    /**
102     * Called while a drag operation is ongoing, when the mouse pointer has
103     * exited the operable part of the drop site for the
104     * {@code DropTarget} registered with this listener.
105     *
106     * @param dte the {@code DropTargetEvent}
107     */
108    public void dragExit(DropTargetEvent dte) {}
109}
110