net.sourceforge.phpeclipse.ui/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
  20  * <code>TransferDropTargetListener</code>s On <code>dragEnter</code> the
  21  * adapter determines the listener to be used for any further <code>drag*</code>
  22  * callback.
  23  */
  24 public class DelegatingDropAdapter implements DropTargetListener {
  25
  26         private TransferDropTargetListener[] fListeners;
  27
  28         private TransferDropTargetListener fChosenListener;
  29
  30         /**
  31          * Creates a new delegating drop adapter.
  32          *
  33          * @param listeners
  34          *            an array of potential listeners
  35          */
  36         public DelegatingDropAdapter(TransferDropTargetListener[] listeners) {
  37                 fListeners = listeners;
  38                 Assert.isNotNull(listeners);
  39         }
  40
  41         /*
  42          * non Java-doc
  43          *
  44          * @see DropTargetListener
  45          */
  46         public void dragEnter(DropTargetEvent event) {
  47                 fChosenListener = null;
  48                 event.currentDataType = selectPreferredListener(event.dataTypes);
  49                 if (fChosenListener != null)
  50                         fChosenListener.dragEnter(event);
  51         }
  52
  53         /*
  54          * non Java-doc
  55          *
  56          * @see DropTargetListener
  57          */
  58         public void dragLeave(DropTargetEvent event) {
  59                 if (fChosenListener != null)
  60                         fChosenListener.dragLeave(event);
  61         }
  62
  63         /*
  64          * non Java-doc
  65          *
  66          * @see DropTargetListener
  67          */
  68         public void dragOperationChanged(DropTargetEvent event) {
  69                 if (fChosenListener != null)
  70                         fChosenListener.dragOperationChanged(event);
  71         }
  72
  73         /*
  74          * non Java-doc
  75          *
  76          * @see DropTargetListener
  77          */
  78         public void dragOver(DropTargetEvent event) {
  79                 if (fChosenListener != null)
  80                         fChosenListener.dragOver(event);
  81         }
  82
  83         /*
  84          * non Java-doc
  85          *
  86          * @see DropTargetListener
  87          */
  88         public void drop(DropTargetEvent event) {
  89                 if (fChosenListener != null)
  90                         fChosenListener.drop(event);
  91                 fChosenListener = null;
  92         }
  93
  94         /*
  95          * non Java-doc
  96          *
  97          * @see DropTargetListener
  98          */
  99         public void dropAccept(DropTargetEvent event) {
 100                 if (fChosenListener != null)
 101                         fChosenListener.dropAccept(event);
 102         }
 103
 104         private TransferData selectPreferredListener(TransferData[] dataTypes) {
 105                 for (int i = 0; i < fListeners.length; i++) {
 106                         TransferData data = computeTransferData(dataTypes, fListeners[i]);
 107                         if (data != null)
 108                                 return data;
 109                 }
 110                 return null;
 111         }
 112
 113         private TransferData computeTransferData(TransferData[] dataTypes,
 114                         TransferDropTargetListener listener) {
 115                 for (int i = 0; i < dataTypes.length; i++) {
 116                         if (listener.getTransfer().isSupportedType(dataTypes[i])) {
 117                                 fChosenListener = listener;
 118                                 return dataTypes[i];
 119                         }
 120                 }
 121                 return null;
 122         }
 123 }