1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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10 *
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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
26 package java.awt.dnd;
27
28 /**
29 * An abstract adapter class for receiving drag source 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 DragSourceEvent} listener
34 * and override the methods for the events of interest. (If you implement the
35 * {@code DragSourceListener} interface, you have to define all of
36 * the methods in it. This abstract class defines null methods for them
37 * all, so you only have to define methods for events you care about.)
38 * <p>
39 * Create a listener object using the extended class and then register it with
40 * a {@code DragSource}. When the drag enters, moves over, or exits
41 * a drop site, when the drop action changes, and when the drag ends, the
42 * relevant method in the listener object is invoked, and the
43 * {@code DragSourceEvent} is passed to it.
44 * <p>
45 * The drop site is <i>associated with the previous {@code dragEnter()}
46 * invocation</i> if the latest invocation of {@code dragEnter()} on this
47 * adapter corresponds to that drop site and is not followed by a
48 * {@code dragExit()} invocation on this adapter.
49 *
50 * @see DragSourceEvent
51 * @see DragSourceListener
52 * @see DragSourceMotionListener
53 *
54 * @author David Mendenhall
55 * @since 1.4
56 */
57 public abstract class DragSourceAdapter
58 implements DragSourceListener, DragSourceMotionListener {
59
60 /**
61 * Constructs a {@code DragSourceAdapter}.
62 */
63 protected DragSourceAdapter() {}
64
65 /**
66 * Called as the cursor's hotspot enters a platform-dependent drop site.
67 * This method is invoked when all the following conditions are true:
68 * <UL>
69 * <LI>The cursor's hotspot enters the operable part of
70 * a platform-dependent drop site.
71 * <LI>The drop site is active.
72 * <LI>The drop site accepts the drag.
73 * </UL>
74 *
75 * @param dsde the {@code DragSourceDragEvent}
76 */
77 public void dragEnter(DragSourceDragEvent dsde) {}
78
79 /**
80 * Called as the cursor's hotspot moves over a platform-dependent drop site.
81 * This method is invoked when all the following conditions are true:
82 * <UL>
83 * <LI>The cursor's hotspot has moved, but still intersects the
84 * operable part of the drop site associated with the previous
85 * dragEnter() invocation.
86 * <LI>The drop site is still active.
87 * <LI>The drop site accepts the drag.
88 * </UL>
89 *
90 * @param dsde the {@code DragSourceDragEvent}
91 */
92 public void dragOver(DragSourceDragEvent dsde) {}
93
94 /**
95 * Called whenever the mouse is moved during a drag operation.
96 *
97 * @param dsde the {@code DragSourceDragEvent}
98 */
99 public void dragMouseMoved(DragSourceDragEvent dsde) {}
100
101 /**
102 * Called when the user has modified the drop gesture.
103 * This method is invoked when the state of the input
104 * device(s) that the user is interacting with changes.
105 * Such devices are typically the mouse buttons or keyboard
106 * modifiers that the user is interacting with.
107 *
108 * @param dsde the {@code DragSourceDragEvent}
109 */
110 public void dropActionChanged(DragSourceDragEvent dsde) {}
111
112 /**
113 * Called as the cursor's hotspot exits a platform-dependent drop site.
114 * This method is invoked when any of the following conditions are true:
115 * <UL>
116 * <LI>The cursor's hotspot no longer intersects the operable part
117 * of the drop site associated with the previous dragEnter() invocation.
118 * </UL>
119 * OR
120 * <UL>
121 * <LI>The drop site associated with the previous dragEnter() invocation
122 * is no longer active.
123 * </UL>
124 * OR
125 * <UL>
126 * <LI> The drop site associated with the previous dragEnter() invocation
127 * has rejected the drag.
128 * </UL>
129 *
130 * @param dse the {@code DragSourceEvent}
131 */
132 public void dragExit(DragSourceEvent dse) {}
133
134 /**
135 * This method is invoked to signify that the Drag and Drop
136 * operation is complete. The getDropSuccess() method of
137 * the {@code DragSourceDropEvent} can be used to
138 * determine the termination state. The getDropAction() method
139 * returns the operation that the drop site selected
140 * to apply to the Drop operation. Once this method is complete, the
141 * current {@code DragSourceContext} and
142 * associated resources become invalid.
143 *
144 * @param dsde the {@code DragSourceDropEvent}
145 */
146 public void dragDropEnd(DragSourceDropEvent dsde) {}
147 }