net.sourceforge.phpeclipse/src/net/sourceforge/phpdt/internal/ui/dnd/DelegatingDropAdapter.java

   1 /*******************************************************************************
   2  * Copyright (c) 2000, 2003 IBM Corporation and others.
   3  * All rights reserved. This program and the accompanying materials
   4  * are made available under the terms of the Common Public License v1.0
   5  * which accompanies this distribution, and is available at
   6  * http://www.eclipse.org/legal/cpl-v10.html
   7  *
   8  * Contributors:
   9  *     IBM Corporation - initial API and implementation
  10  *******************************************************************************/
  11 package net.sourceforge.phpdt.internal.ui.dnd;
  12
  13 import org.eclipse.jface.util.Assert;
  14 import org.eclipse.swt.dnd.DropTargetEvent;
  15 import org.eclipse.swt.dnd.DropTargetListener;
  16 import org.eclipse.swt.dnd.TransferData;
  17
  18 /**
  19  * A delegating drop adapter negotiates between a set of <code>TransferDropTargetListener</code>s
  20  * On <code>dragEnter</code> the adapter determines the listener to be used for any further
  21  * <code>drag*</code> callback.
  22  */
  23 public class DelegatingDropAdapter implements DropTargetListener {
  24
  25         private TransferDropTargetListener[] fListeners;
  26
  27         private TransferDropTargetListener fChosenListener;
  28
  29         /**
  30          * Creates a new delegating drop adapter.
  31          *
  32          * @param listeners an array of potential listeners
  33          */
  34         public DelegatingDropAdapter(TransferDropTargetListener[] listeners) {
  35                 fListeners= listeners;
  36                 Assert.isNotNull(listeners);
  37         }
  38
  39         /* non Java-doc
  40          * @see DropTargetListener
  41          */
  42         public void dragEnter(DropTargetEvent event) {
  43                 fChosenListener= null;
  44                 event.currentDataType= selectPreferredListener(event.dataTypes);
  45                 if (fChosenListener != null)
  46                         fChosenListener.dragEnter(event);
  47         }
  48
  49         /* non Java-doc
  50          * @see DropTargetListener
  51          */
  52         public void dragLeave(DropTargetEvent event){
  53                 if (fChosenListener != null)
  54                         fChosenListener.dragLeave(event);
  55         }
  56
  57         /* non Java-doc
  58          * @see DropTargetListener
  59          */
  60         public void dragOperationChanged(DropTargetEvent event){
  61                 if (fChosenListener != null)
  62                         fChosenListener.dragOperationChanged(event);
  63         }
  64
  65         /* non Java-doc
  66          * @see DropTargetListener
  67          */
  68         public void dragOver(DropTargetEvent event){
  69                 if (fChosenListener != null)
  70                         fChosenListener.dragOver(event);
  71         }
  72
  73         /* non Java-doc
  74          * @see DropTargetListener
  75          */
  76         public void drop(DropTargetEvent event){
  77                 if (fChosenListener != null)
  78                         fChosenListener.drop(event);
  79                 fChosenListener= null;
  80         }
  81
  82         /* non Java-doc
  83          * @see DropTargetListener
  84          */
  85         public void dropAccept(DropTargetEvent event){
  86                 if (fChosenListener != null)
  87                         fChosenListener.dropAccept(event);
  88         }
  89
  90         private TransferData selectPreferredListener(TransferData[] dataTypes) {
  91                 for (int i= 0; i < fListeners.length; i++) {
  92                         TransferData data= computeTransferData(dataTypes, fListeners[i]);
  93                         if (data != null)
  94                                 return data;
  95                 }
  96                 return null;
  97         }
  98
  99         private TransferData computeTransferData(TransferData[] dataTypes, TransferDropTargetListener listener) {
 100                 for (int i= 0; i < dataTypes.length; i++) {
 101                         if (listener.getTransfer().isSupportedType(dataTypes[i])) {
 102                                 fChosenListener= listener;
 103                                 return dataTypes[i];
 104                         }
 105                 }
 106                 return null;
 107         }
 108 }