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    3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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    5    * This code is free software; you can redistribute it and/or modify it
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    8    * particular file as subject to the "Classpath" exception as provided
    9    * by Oracle 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
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   19    * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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   23    * questions.
   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</code> listener
   34    * and override the methods for the events of interest. (If you implement the
   35    * <code>DragSourceListener</code> 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</code>. 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</code> is passed to it.
   44    * <p>
   45    * The drop site is <i>associated with the previous <code>dragEnter()</code>
   46    * invocation</i> if the latest invocation of <code>dragEnter()</code> on this
   47    * adapter corresponds to that drop site and is not followed by a
   48    * <code>dragExit()</code> 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        * Called as the cursor's hotspot enters a platform-dependent drop site.
   62        * This method is invoked when all the following conditions are true:
   63        * <UL>
   64        * <LI>The cursor's hotspot enters the operable part of
   65        * a platform-dependent drop site.
   66        * <LI>The drop site is active.
   67        * <LI>The drop site accepts the drag.
   68        * </UL>
   69        *
   70        * @param dsde the <code>DragSourceDragEvent</code>
   71        */
   72       public void dragEnter(DragSourceDragEvent dsde) {}
   73   
   74       /**
   75        * Called as the cursor's hotspot moves over a platform-dependent drop site.
   76        * This method is invoked when all the following conditions are true:
   77        * <UL>
   78        * <LI>The cursor's hotspot has moved, but still intersects the
   79        * operable part of the drop site associated with the previous
   80        * dragEnter() invocation.
   81        * <LI>The drop site is still active.
   82        * <LI>The drop site accepts the drag.
   83        * </UL>
   84        *
   85        * @param dsde the <code>DragSourceDragEvent</code>
   86        */
   87       public void dragOver(DragSourceDragEvent dsde) {}
   88   
   89       /**
   90        * Called whenever the mouse is moved during a drag operation.
   91        *
   92        * @param dsde the <code>DragSourceDragEvent</code>
   93        */
   94       public void dragMouseMoved(DragSourceDragEvent dsde) {}
   95   
   96       /**
   97        * Called when the user has modified the drop gesture.
   98        * This method is invoked when the state of the input
   99        * device(s) that the user is interacting with changes.
  100        * Such devices are typically the mouse buttons or keyboard
  101        * modifiers that the user is interacting with.
  102        *
  103        * @param dsde the <code>DragSourceDragEvent</code>
  104        */
  105       public void dropActionChanged(DragSourceDragEvent dsde) {}
  106   
  107       /**
  108        * Called as the cursor's hotspot exits a platform-dependent drop site.
  109        * This method is invoked when any of the following conditions are true:
  110        * <UL>
  111        * <LI>The cursor's hotspot no longer intersects the operable part
  112        * of the drop site associated with the previous dragEnter() invocation.
  113        * </UL>
  114        * OR
  115        * <UL>
  116        * <LI>The drop site associated with the previous dragEnter() invocation
  117        * is no longer active.
  118        * </UL>
  119        * OR
  120        * <UL>
  121        * <LI> The drop site associated with the previous dragEnter() invocation
  122        * has rejected the drag.
  123        * </UL>
  124        *
  125        * @param dse the <code>DragSourceEvent</code>
  126        */
  127       public void dragExit(DragSourceEvent dse) {}
  128   
  129       /**
  130        * This method is invoked to signify that the Drag and Drop
  131        * operation is complete. The getDropSuccess() method of
  132        * the <code>DragSourceDropEvent</code> can be used to
  133        * determine the termination state. The getDropAction() method
  134        * returns the operation that the drop site selected
  135        * to apply to the Drop operation. Once this method is complete, the
  136        * current <code>DragSourceContext</code> and
  137        * associated resources become invalid.
  138        *
  139        * @param dsde the <code>DragSourceDropEvent</code>
  140        */
  141       public void dragDropEnd(DragSourceDropEvent dsde) {}
  142   }

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