1 /*
2 * Copyright 1997-2007 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun in the LICENSE file that accompanied this code.
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).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package java.awt.dnd;
27
28 import java.util.EventListener;
29
30 import java.awt.dnd.DropTargetDragEvent;
31 import java.awt.dnd.DropTargetDropEvent;
32
33 /**
34 * The <code>DropTargetListener</code> interface
35 * is the callback interface used by the
36 * <code>DropTarget</code> class to provide
37 * notification of DnD operations that involve
38 * the subject <code>DropTarget</code>. Methods of
39 * this interface may be implemented to provide
40 * "drag under" visual feedback to the user throughout
41 * the Drag and Drop operation.
42 * <p>
43 * Create a listener object by implementing the interface and then register it
44 * with a <code>DropTarget</code>. When the drag enters, moves over, or exits
45 * the operable part of the drop site for that <code>DropTarget</code>, when
46 * the drop action changes, and when the drop occurs, the relevant method in
47 * the listener object is invoked, and the <code>DropTargetEvent</code> is
48 * passed to it.
49 * <p>
50 * The operable part of the drop site for the <code>DropTarget</code> is
51 * the part of the associated <code>Component</code>'s geometry that is not
52 * obscured by an overlapping top-level window or by another
53 * <code>Component</code> higher in the Z-order that has an associated active
54 * <code>DropTarget</code>.
55 * <p>
56 * During the drag, the data associated with the current drag operation can be
57 * retrieved by calling <code>getTransferable()</code> on
58 * <code>DropTargetDragEvent</code> instances passed to the listener's
59 * methods.
60 * <p>
61 * Note that <code>getTransferable()</code> on the
62 * <code>DropTargetDragEvent</code> instance should only be called within the
63 * respective listener's method and all the necessary data should be retrieved
64 * from the returned <code>Transferable</code> before that method returns.
65 *
66 * @since 1.2
67 */
68
69 public interface DropTargetListener extends EventListener {
70
71 /**
72 * Called while a drag operation is ongoing, when the mouse pointer enters
73 * the operable part of the drop site for the <code>DropTarget</code>
74 * registered with this listener.
75 *
76 * @param dtde the <code>DropTargetDragEvent</code>
77 */
78
79 void dragEnter(DropTargetDragEvent dtde);
80
81 /**
82 * Called when a drag operation is ongoing, while the mouse pointer is still
83 * over the operable part of the drop site for the <code>DropTarget</code>
84 * registered with this listener.
85 *
86 * @param dtde the <code>DropTargetDragEvent</code>
87 */
88
89 void dragOver(DropTargetDragEvent dtde);
90
91 /**
92 * Called if the user has modified
93 * the current drop gesture.
94 * <P>
95 * @param dtde the <code>DropTargetDragEvent</code>
96 */
97
98 void dropActionChanged(DropTargetDragEvent dtde);
99
100 /**
101 * Called while a drag operation is ongoing, when the mouse pointer has
102 * exited the operable part of the drop site for the
103 * <code>DropTarget</code> registered with this listener.
104 *
105 * @param dte the <code>DropTargetEvent</code>
106 */
107
108 void dragExit(DropTargetEvent dte);
109
110 /**
111 * Called when the drag operation has terminated with a drop on
112 * the operable part of the drop site for the <code>DropTarget</code>
113 * registered with this listener.
114 * <p>
115 * This method is responsible for undertaking
116 * the transfer of the data associated with the
117 * gesture. The <code>DropTargetDropEvent</code>
118 * provides a means to obtain a <code>Transferable</code>
119 * object that represents the data object(s) to
120 * be transfered.<P>
121 * From this method, the <code>DropTargetListener</code>
122 * shall accept or reject the drop via the
123 * acceptDrop(int dropAction) or rejectDrop() methods of the
124 * <code>DropTargetDropEvent</code> parameter.
125 * <P>
126 * Subsequent to acceptDrop(), but not before,
127 * <code>DropTargetDropEvent</code>'s getTransferable()
128 * method may be invoked, and data transfer may be
129 * performed via the returned <code>Transferable</code>'s
130 * getTransferData() method.
131 * <P>
132 * At the completion of a drop, an implementation
133 * of this method is required to signal the success/failure
134 * of the drop by passing an appropriate
135 * <code>boolean</code> to the <code>DropTargetDropEvent</code>'s
136 * dropComplete(boolean success) method.
137 * <P>
138 * Note: The data transfer should be completed before the call to the
139 * <code>DropTargetDropEvent</code>'s dropComplete(boolean success) method.
140 * After that, a call to the getTransferData() method of the
141 * <code>Transferable</code> returned by
142 * <code>DropTargetDropEvent.getTransferable()</code> is guaranteed to
143 * succeed only if the data transfer is local; that is, only if
144 * <code>DropTargetDropEvent.isLocalTransfer()</code> returns
145 * <code>true</code>. Otherwise, the behavior of the call is
146 * implementation-dependent.
147 * <P>
148 * @param dtde the <code>DropTargetDropEvent</code>
149 */
150
151 void drop(DropTargetDropEvent dtde);
152 }
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