DropTargetDragEvent


1   /*
2    * @(#)DropTargetDragEvent.java 1.24 04/05/05
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  import java.awt.Point  ;
11  
12  import java.awt.datatransfer.DataFlavor  ;
13  import java.awt.datatransfer.Transferable  ;
14  
15  import java.util.List  ;
16  
17  /**
18   * The <code>DropTargetDragEvent</code> is delivered to a 
19   * <code>DropTargetListener</code> via its
20   * dragEnter() and dragOver() methods.
21   * <p>
22   * The <code>DropTargetDragEvent</code> reports the <i>source drop actions</i>
23   * and the <i>user drop action</i> that reflect the current state of 
24   * the drag operation.
25   * <p>
26   * <i>Source drop actions</i> is a bitwise mask of <code>DnDConstants</code>
27   * that represents the set of drop actions supported by the drag source for 
28   * this drag operation.
29   * <p>
30   * <i>User drop action</i> depends on the drop actions supported by the drag
31   * source and the drop action selected by the user. The user can select a drop
32   * action by pressing modifier keys during the drag operation: 
33   * <pre> 
34   *   Ctrl + Shift -> ACTION_LINK
35   *   Ctrl         -> ACTION_COPY
36   *   Shift        -> ACTION_MOVE
37   * </pre> 
38   * If the user selects a drop action, the <i>user drop action</i> is one of 
39   * <code>DnDConstants</code> that represents the selected drop action if this
40   * drop action is supported by the drag source or
41   * <code>DnDConstants.ACTION_NONE</code> if this drop action is not supported 
42   * by the drag source.
43   * <p>
44   * If the user doesn't select a drop action, the set of
45   * <code>DnDConstants</code> that represents the set of drop actions supported
46   * by the drag source is searched for <code>DnDConstants.ACTION_MOVE</code>,
47   * then for <code>DnDConstants.ACTION_COPY</code>, then for
48   * <code>DnDConstants.ACTION_LINK</code> and the <i>user drop action</i> is the
49   * first constant found. If no constant is found the <i>user drop action</i>
50   * is <code>DnDConstants.ACTION_NONE</code>.
51   *
52   * @version     1.24, 05/05/04
53   * @since 1.2
54   */
55  
56  public class DropTargetDragEvent extends DropTargetEvent   {
57  
58      private static final long serialVersionUID = -8422265619058953682L;
59  
60      /**
61       * Construct a <code>DropTargetDragEvent</code> given the
62       * <code>DropTargetContext</code> for this operation,
63       * the location of the "Drag" <code>Cursor</code>'s hotspot 
64       * in the <code>Component</code>'s coordinates, the
65       * user drop action, and the source drop actions.
66       * <P>
67       * @param dtc        The DropTargetContext for this operation
68       * @param cursorLocn The location of the "Drag" Cursor's 
69       * hotspot in Component coordinates
70       * @param dropAction The user drop action
71       * @param srcActions The source drop actions
72       * 
73       * @throws NullPointerException if cursorLocn is null
74       * @throws <code>IllegalArgumentException</code> if dropAction is not one of
75       *         <code>DnDConstants</code>.
76       * @throws <code>IllegalArgumentException</code> if srcActions is not
77       *         a bitwise mask of <code>DnDConstants</code>.
78       * @throws <code>IllegalArgumentException</code> if dtc is <code>null</code>.
79       */
80  
81      public DropTargetDragEvent(DropTargetContext   dtc, Point   cursorLocn, int dropAction, int srcActions)  {
82      super(dtc);
83  
84      if (cursorLocn == null) throw new NullPointerException  ("cursorLocn");
85  
86      if (dropAction != DnDConstants.ACTION_NONE &&
87          dropAction != DnDConstants.ACTION_COPY &&
88          dropAction != DnDConstants.ACTION_MOVE &&
89          dropAction != DnDConstants.ACTION_LINK
90      ) throw new IllegalArgumentException  ("dropAction" + dropAction);
91  
92      if ((srcActions & ~(DnDConstants.ACTION_COPY_OR_MOVE | DnDConstants.ACTION_LINK)) != 0) throw new IllegalArgumentException  ("srcActions");
93  
94      location        = cursorLocn;
95      actions         = srcActions;
96      this.dropAction = dropAction;
97      }
98  
99      /**
100      * This method returns a <code>Point</code>
101      * indicating the <code>Cursor</code>'s current
102      * location within the <code>Component'</code>s
103      * coordinates.
104      * <P>
105      * @return the current cursor location in 
106      * <code>Component</code>'s coords.
107      */
108 
109     public Point   getLocation() {
110     return location;
111     }
112 
113 
114     /**
115      * This method returns the current <code>DataFlavor</code>s from the
116      * <code>DropTargetContext</code>.
117      * <P>
118      * @return current DataFlavors from the DropTargetContext
119      */
120 
121     public DataFlavor  [] getCurrentDataFlavors() {
122     return getDropTargetContext().getCurrentDataFlavors();
123     }
124 
125     /**
126      * This method returns the current <code>DataFlavor</code>s
127      * as a <code>java.util.List</code>
128      * <P>
129      * @return a <code>java.util.List</code> of the Current <code>DataFlavor</code>s
130      */
131 
132     public List  <DataFlavor  > getCurrentDataFlavorsAsList() {
133     return getDropTargetContext().getCurrentDataFlavorsAsList();
134     }
135 
136     /**
137      * This method returns a <code>boolean</code> indicating
138      * if the specified <code>DataFlavor</code> is supported.
139      * <P>
140      * @param df the <code>DataFlavor</code> to test
141      * <P>
142      * @return if a particular DataFlavor is supported
143      */
144 
145     public boolean isDataFlavorSupported(DataFlavor   df) {
146     return getDropTargetContext().isDataFlavorSupported(df);
147     }
148 
149     /**
150      * This method returns the source drop actions.
151      * 
152      * @return the source drop actions
153      */
154     public int getSourceActions() { return actions; }
155 
156     /**
157      * This method returns the user drop action.
158      * 
159      * @return the user drop action
160      */
161     public int getDropAction() { return dropAction; }
162 
163     /**
164      * This method returns the Transferable object that represents
165      * the data associated with the current drag operation.
166      * 
167      * @return the Transferable associated with the drag operation
168      * @throws InvalidDnDOperationException if the data associated with the drag
169      *         operation is not available
170      *
171      * @since 1.5
172      */
173     public Transferable   getTransferable() {
174     return getDropTargetContext().getTransferable();
175     }
176 
177     /**
178      * Accepts the drag.
179      *
180      * This method should be called from a
181      * <code>DropTargetListeners</code> <code>dragEnter</code>,
182      * <code>dragOver</code>, and <code>dropActionChanged</code>
183      * methods if the implementation wishes to accept an operation
184      * from the srcActions other than the one selected by
185      * the user as represented by the <code>dropAction</code>.
186      * 
187      * @param dragOperation the operation accepted by the target
188      */
189     public void acceptDrag(int dragOperation) {
190     getDropTargetContext().acceptDrag(dragOperation);
191     }
192 
193     /**
194      * Rejects the drag as a result of examining either the
195      * <code>dropAction</code> or the available <code>DataFlavor</code>
196      * types.
197      */
198     public void rejectDrag() {
199     getDropTargetContext().rejectDrag();
200     }
201 
202     /*
203      * fields
204      */
205 
206     /**
207      * The location of the drag cursor's hotspot in Component coordinates.
208      *
209      * @serial
210      */
211     private Point         location;
212 
213     /**
214      * The source drop actions.
215      *
216      * @serial
217      */
218     private int         actions;
219 
220     /**
221      * The user drop action.
222      *
223      * @serial
224      */
225     private int         dropAction;
226 }
227
A to Z: JavaDoc & Examples Daily Java News & Articles Open Source Projects Open Source Codes Free Computer Books Remove Frame
Popular Tags