DragSourceAdapter


1   /*
2    * @(#)DragSourceAdapter.java   1.6 03/12/19
3    *
4    * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6    */
7   
8   package java.awt.dnd;
9   
10  /**
11   * An abstract adapter class for receiving drag source events. The methods in
12   * this class are empty. This class exists only as a convenience for creating
13   * listener objects.
14   * <p>
15   * Extend this class to create a <code>DragSourceEvent</code> listener 
16   * and override the methods for the events of interest. (If you implement the 
17   * <code>DragSourceListener</code> interface, you have to define all of
18   * the methods in it. This abstract class defines null methods for them
19   * all, so you only have to define methods for events you care about.)
20   * <p>
21   * Create a listener object using the extended class and then register it with 
22   * a <code>DragSource</code>. When the drag enters, moves over, or exits
23   * a drop site, when the drop action changes, and when the drag ends, the
24   * relevant method in the listener object is invoked, and the
25   * <code>DragSourceEvent</code> is passed to it.
26   * <p>
27   * The drop site is <i>associated with the previous <code>dragEnter()</code>
28   * invocation</i> if the latest invocation of <code>dragEnter()</code> on this
29   * adapter corresponds to that drop site and is not followed by a
30   * <code>dragExit()</code> invocation on this adapter.
31   *
32   * @see DragSourceEvent
33   * @see DragSourceListener
34   * @see DragSourceMotionListener
35   *
36   * @author David Mendenhall
37   * @version 1.6, 12/19/03
38   * @since 1.4
39   */
40  public abstract class DragSourceAdapter 
41      implements DragSourceListener  , DragSourceMotionListener   { 
42  
43      /**
44       * Called as the cursor's hotspot enters a platform-dependent drop site.
45       * This method is invoked when all the following conditions are true:
46       * <UL>
47       * <LI>The cursor's hotspot enters the operable part of 
48       * a platform-dependent drop site.
49       * <LI>The drop site is active.
50       * <LI>The drop site accepts the drag.
51       * </UL>
52       *
53       * @param dsde the <code>DragSourceDragEvent</code>
54       */
55      public void dragEnter(DragSourceDragEvent   dsde) {}
56  
57      /**
58       * Called as the cursor's hotspot moves over a platform-dependent drop site.
59       * This method is invoked when all the following conditions are true:
60       * <UL>
61       * <LI>The cursor's hotspot has moved, but still intersects the 
62       * operable part of the drop site associated with the previous
63       * dragEnter() invocation.
64       * <LI>The drop site is still active.
65       * <LI>The drop site accepts the drag.
66       * </UL>
67       *
68       * @param dsde the <code>DragSourceDragEvent</code>
69       */
70      public void dragOver(DragSourceDragEvent   dsde) {}
71  
72      /**
73       * Called whenever the mouse is moved during a drag operation.
74       * 
75       * @param dsde the <code>DragSourceDragEvent</code>
76       */
77      public void dragMouseMoved(DragSourceDragEvent   dsde) {}
78  
79      /**
80       * Called when the user has modified the drop gesture.
81       * This method is invoked when the state of the input
82       * device(s) that the user is interacting with changes.
83       * Such devices are typically the mouse buttons or keyboard
84       * modifiers that the user is interacting with.
85       *
86       * @param dsde the <code>DragSourceDragEvent</code>
87       */
88      public void dropActionChanged(DragSourceDragEvent   dsde) {}
89  
90      /**
91       * Called as the cursor's hotspot exits a platform-dependent drop site.
92       * This method is invoked when any of the following conditions are true:
93       * <UL>
94       * <LI>The cursor's hotspot no longer intersects the operable part
95       * of the drop site associated with the previous dragEnter() invocation.
96       * </UL>
97       * OR
98       * <UL>
99       * <LI>The drop site associated with the previous dragEnter() invocation
100      * is no longer active.
101      * </UL>
102      * OR
103      * <UL>
104      * <LI> The drop site associated with the previous dragEnter() invocation
105      * has rejected the drag. 
106      * </UL>
107      * 
108      * @param dse the <code>DragSourceEvent</code>
109      */
110     public void dragExit(DragSourceEvent   dse) {}
111 
112     /**
113      * This method is invoked to signify that the Drag and Drop
114      * operation is complete. The getDropSuccess() method of
115      * the <code>DragSourceDropEvent</code> can be used to 
116      * determine the termination state. The getDropAction() method
117      * returns the operation that the drop site selected 
118      * to apply to the Drop operation. Once this method is complete, the
119      * current <code>DragSourceContext</code> and
120      * associated resources become invalid.
121      *
122      * @param dsde the <code>DragSourceDropEvent</code>
123      */
124     public void dragDropEnd(DragSourceDropEvent   dsde) {}
125 }
126
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