1 /*
   2  * Copyright (c) 1997, 2004, Oracle and/or its affiliates. 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.  Oracle designates this
   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
  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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.awt.dnd;
  27 
  28 import java.awt.Component;
  29 
  30 import java.awt.datatransfer.DataFlavor;
  31 import java.awt.datatransfer.Transferable;
  32 import java.awt.datatransfer.UnsupportedFlavorException;
  33 
  34 import java.awt.dnd.peer.DropTargetContextPeer;
  35 
  36 import java.io.IOException;
  37 import java.io.Serializable;
  38 
  39 import java.util.Arrays;
  40 import java.util.List;
  41 
  42 
  43 /**
  44  * A <code>DropTargetContext</code> is created
  45  * whenever the logical cursor associated
  46  * with a Drag and Drop operation coincides with the visible geometry of
  47  * a <code>Component</code> associated with a <code>DropTarget</code>.
  48  * The <code>DropTargetContext</code> provides
  49  * the mechanism for a potential receiver
  50  * of a drop operation to both provide the end user with the appropriate
  51  * drag under feedback, but also to effect the subsequent data transfer
  52  * if appropriate.
  53  *
  54  * @since 1.2
  55  */
  56 
  57 public class DropTargetContext implements Serializable {
  58 
  59     private static final long serialVersionUID = -634158968993743371L;
  60 
  61     /**
  62      * Construct a <code>DropTargetContext</code>
  63      * given a specified <code>DropTarget</code>.
  64      *
  65      * @param dt the DropTarget to associate with
  66      */
  67 
  68     DropTargetContext(DropTarget dt) {
  69         super();
  70 
  71         dropTarget = dt;
  72     }
  73 
  74     /**
  75      * This method returns the <code>DropTarget</code> associated with this
  76      * <code>DropTargetContext</code>.
  77      *
  78      * @return the <code>DropTarget</code> associated with this <code>DropTargetContext</code>
  79      */
  80 
  81     public DropTarget getDropTarget() { return dropTarget; }
  82 
  83     /**
  84      * This method returns the <code>Component</code> associated with
  85      * this <code>DropTargetContext</code>.
  86      *
  87      * @return the Component associated with this Context
  88      */
  89 
  90     public Component getComponent() { return dropTarget.getComponent(); }
  91 
  92     /**
  93      * Called when associated with the <code>DropTargetContextPeer</code>.
  94      *
  95      * @param dtcp the <code>DropTargetContextPeer</code>
  96      */
  97 
  98     public void addNotify(DropTargetContextPeer dtcp) {
  99         dropTargetContextPeer = dtcp;
 100     }
 101 
 102     /**
 103      * Called when disassociated with the <code>DropTargetContextPeer</code>.
 104      */
 105 
 106     public void removeNotify() {
 107         dropTargetContextPeer = null;
 108         transferable          = null;
 109     }
 110 
 111     /**
 112      * This method sets the current actions acceptable to
 113      * this <code>DropTarget</code>.
 114      *
 115      * @param actions an <code>int</code> representing the supported action(s)
 116      */
 117 
 118     protected void setTargetActions(int actions) {
 119         DropTargetContextPeer peer = getDropTargetContextPeer();
 120         if (peer != null) {
 121             synchronized (peer) {
 122                 peer.setTargetActions(actions);
 123                 getDropTarget().doSetDefaultActions(actions);
 124             }
 125         } else {
 126             getDropTarget().doSetDefaultActions(actions);
 127         }
 128     }
 129 
 130     /**
 131      * This method returns an <code>int</code> representing the
 132      * current actions this <code>DropTarget</code> will accept.
 133      *
 134      * @return the current actions acceptable to this <code>DropTarget</code>
 135      */
 136 
 137     protected int getTargetActions() {
 138         DropTargetContextPeer peer = getDropTargetContextPeer();
 139         return ((peer != null)
 140                         ? peer.getTargetActions()
 141                         : dropTarget.getDefaultActions()
 142         );
 143     }
 144 
 145     /**
 146      * This method signals that the drop is completed and
 147      * if it was successful or not.
 148      *
 149      * @param success true for success, false if not
 150      *
 151      * @throws InvalidDnDOperationException if a drop is not outstanding/extant
 152      */
 153 
 154     public void dropComplete(boolean success) throws InvalidDnDOperationException{
 155         DropTargetContextPeer peer = getDropTargetContextPeer();
 156         if (peer != null) {
 157             peer.dropComplete(success);
 158         }
 159     }
 160 
 161     /**
 162      * accept the Drag.
 163      *
 164      * @param dragOperation the supported action(s)
 165      */
 166 
 167     protected void acceptDrag(int dragOperation) {
 168         DropTargetContextPeer peer = getDropTargetContextPeer();
 169         if (peer != null) {
 170             peer.acceptDrag(dragOperation);
 171         }
 172     }
 173 
 174     /**
 175      * reject the Drag.
 176      */
 177 
 178     protected void rejectDrag() {
 179         DropTargetContextPeer peer = getDropTargetContextPeer();
 180         if (peer != null) {
 181             peer.rejectDrag();
 182         }
 183     }
 184 
 185     /**
 186      * called to signal that the drop is acceptable
 187      * using the specified operation.
 188      * must be called during DropTargetListener.drop method invocation.
 189      *
 190      * @param dropOperation the supported action(s)
 191      */
 192 
 193     protected void acceptDrop(int dropOperation) {
 194         DropTargetContextPeer peer = getDropTargetContextPeer();
 195         if (peer != null) {
 196             peer.acceptDrop(dropOperation);
 197         }
 198     }
 199 
 200     /**
 201      * called to signal that the drop is unacceptable.
 202      * must be called during DropTargetListener.drop method invocation.
 203      */
 204 
 205     protected void rejectDrop() {
 206         DropTargetContextPeer peer = getDropTargetContextPeer();
 207         if (peer != null) {
 208             peer.rejectDrop();
 209         }
 210     }
 211 
 212     /**
 213      * get the available DataFlavors of the
 214      * <code>Transferable</code> operand of this operation.
 215      *
 216      * @return a <code>DataFlavor[]</code> containing the
 217      * supported <code>DataFlavor</code>s of the
 218      * <code>Transferable</code> operand.
 219      */
 220 
 221     protected DataFlavor[] getCurrentDataFlavors() {
 222         DropTargetContextPeer peer = getDropTargetContextPeer();
 223         return peer != null ? peer.getTransferDataFlavors() : new DataFlavor[0];
 224     }
 225 
 226     /**
 227      * This method returns a the currently available DataFlavors
 228      * of the <code>Transferable</code> operand
 229      * as a <code>java.util.List</code>.
 230      *
 231      * @return the currently available
 232      * DataFlavors as a <code>java.util.List</code>
 233      */
 234 
 235     protected List<DataFlavor> getCurrentDataFlavorsAsList() {
 236         return Arrays.asList(getCurrentDataFlavors());
 237     }
 238 
 239     /**
 240      * This method returns a <code>boolean</code>
 241      * indicating if the given <code>DataFlavor</code> is
 242      * supported by this <code>DropTargetContext</code>.
 243      *
 244      * @param df the <code>DataFlavor</code>
 245      *
 246      * @return if the <code>DataFlavor</code> specified is supported
 247      */
 248 
 249     protected boolean isDataFlavorSupported(DataFlavor df) {
 250         return getCurrentDataFlavorsAsList().contains(df);
 251     }
 252 
 253     /**
 254      * get the Transferable (proxy) operand of this operation
 255      *
 256      * @throws InvalidDnDOperationException if a drag is not outstanding/extant
 257      *
 258      * @return the <code>Transferable</code>
 259      */
 260 
 261     protected Transferable getTransferable() throws InvalidDnDOperationException {
 262         DropTargetContextPeer peer = getDropTargetContextPeer();
 263         if (peer == null) {
 264             throw new InvalidDnDOperationException();
 265         } else {
 266             if (transferable == null) {
 267                 Transferable t = peer.getTransferable();
 268                 boolean isLocal = peer.isTransferableJVMLocal();
 269                 synchronized (this) {
 270                     if (transferable == null) {
 271                         transferable = createTransferableProxy(t, isLocal);
 272                     }
 273                 }
 274             }
 275 
 276             return transferable;
 277         }
 278     }
 279 
 280     /**
 281      * Get the <code>DropTargetContextPeer</code>
 282      *
 283      * @return the platform peer
 284      */
 285 
 286     DropTargetContextPeer getDropTargetContextPeer() {
 287         return dropTargetContextPeer;
 288     }
 289 
 290     /**
 291      * Creates a TransferableProxy to proxy for the specified
 292      * Transferable.
 293      *
 294      * @param t the <tt>Transferable</tt> to be proxied
 295      * @param local <tt>true</tt> if <tt>t</tt> represents
 296      *        the result of a local drag-n-drop operation.
 297      * @return the new <tt>TransferableProxy</tt> instance.
 298      */
 299     protected Transferable createTransferableProxy(Transferable t, boolean local) {
 300         return new TransferableProxy(t, local);
 301     }
 302 
 303 /****************************************************************************/
 304 
 305 
 306     /**
 307      * <code>TransferableProxy</code> is a helper inner class that implements
 308      * <code>Transferable</code> interface and serves as a proxy for another
 309      * <code>Transferable</code> object which represents data transfer for
 310      * a particular drag-n-drop operation.
 311      * <p>
 312      * The proxy forwards all requests to the encapsulated transferable
 313      * and automatically performs additional conversion on the data
 314      * returned by the encapsulated transferable in case of local transfer.
 315      */
 316 
 317     protected class TransferableProxy implements Transferable {
 318 
 319         /**
 320          * Constructs a <code>TransferableProxy</code> given
 321          * a specified <code>Transferable</code> object representing
 322          * data transfer for a particular drag-n-drop operation and
 323          * a <code>boolean</code> which indicates whether the
 324          * drag-n-drop operation is local (within the same JVM).
 325          *
 326          * @param t the <code>Transferable</code> object
 327          * @param local <code>true</code>, if <code>t</code> represents
 328          *        the result of local drag-n-drop operation
 329          */
 330         TransferableProxy(Transferable t, boolean local) {
 331             proxy = new sun.awt.datatransfer.TransferableProxy(t, local);
 332             transferable = t;
 333             isLocal      = local;
 334         }
 335 
 336         /**
 337          * Returns an array of DataFlavor objects indicating the flavors
 338          * the data can be provided in by the encapsulated transferable.
 339          *
 340          * @return an array of data flavors in which the data can be
 341          *         provided by the encapsulated transferable
 342          */
 343         public DataFlavor[] getTransferDataFlavors() {
 344             return proxy.getTransferDataFlavors();
 345         }
 346 
 347         /**
 348          * Returns whether or not the specified data flavor is supported by
 349          * the encapsulated transferable.
 350          * @param flavor the requested flavor for the data
 351          * @return <code>true</code> if the data flavor is supported,
 352          *         <code>false</code> otherwise
 353          */
 354         public boolean isDataFlavorSupported(DataFlavor flavor) {
 355             return proxy.isDataFlavorSupported(flavor);
 356         }
 357 
 358         /**
 359          * Returns an object which represents the data provided by
 360          * the encapsulated transferable for the requested data flavor.
 361          * <p>
 362          * In case of local transfer a serialized copy of the object
 363          * returned by the encapsulated transferable is provided when
 364          * the data is requested in application/x-java-serialized-object
 365          * data flavor.
 366          *
 367          * @param df the requested flavor for the data
 368          * @throws IOException if the data is no longer available
 369          *              in the requested flavor.
 370          * @throws UnsupportedFlavorException if the requested data flavor is
 371          *              not supported.
 372          */
 373         public Object getTransferData(DataFlavor df)
 374             throws UnsupportedFlavorException, IOException
 375         {
 376             return proxy.getTransferData(df);
 377         }
 378 
 379         /*
 380          * fields
 381          */
 382 
 383         // We don't need to worry about client code changing the values of
 384         // these variables. Since TransferableProxy is a protected class, only
 385         // subclasses of DropTargetContext can access it. And DropTargetContext
 386         // cannot be subclassed by client code because it does not have a
 387         // public constructor.
 388 
 389         /**
 390          * The encapsulated <code>Transferable</code> object.
 391          */
 392         protected Transferable  transferable;
 393 
 394         /**
 395          * A <code>boolean</code> indicating if the encapsulated
 396          * <code>Transferable</code> object represents the result
 397          * of local drag-n-drop operation (within the same JVM).
 398          */
 399         protected boolean       isLocal;
 400 
 401         private sun.awt.datatransfer.TransferableProxy proxy;
 402     }
 403 
 404 /****************************************************************************/
 405 
 406     /*
 407      * fields
 408      */
 409 
 410     /**
 411      * The DropTarget associated with this DropTargetContext.
 412      *
 413      * @serial
 414      */
 415     private DropTarget dropTarget;
 416 
 417     private transient DropTargetContextPeer dropTargetContextPeer;
 418 
 419     private transient Transferable transferable;
 420 }