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.swt.dnd.DropTargetEvent;
  14 import org.eclipse.swt.dnd.DropTargetListener;
  15 import org.eclipse.swt.dnd.TransferData;
  16
  17 import org.eclipse.jface.util.Assert;
  18
  19 /**
  20  * A delegating drop adapter negotiates between a set of <code>TransferDropTargetListener</code>s
  21  * On <code>dragEnter</code> the adapter determines the listener to be used for any further
  22  * <code>drag*</code> 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 an array of potential listeners
  34          */
  35         public DelegatingDropAdapter(TransferDropTargetListener[] listeners) {
  36                 fListeners= listeners;
  37                 Assert.isNotNull(listeners);
  38         }
  39
  40         /* non Java-doc
  41          * @see DropTargetListener
  42          */
  43         public void dragEnter(DropTargetEvent event) {
  44                 fChosenListener= null;
  45                 event.currentDataType= selectPreferredListener(event.dataTypes);
  46                 if (fChosenListener != null)
  47                         fChosenListener.dragEnter(event);
  48         }
  49
  50         /* non Java-doc
  51          * @see DropTargetListener
  52          */
  53         public void dragLeave(DropTargetEvent event){
  54                 if (fChosenListener != null)
  55                         fChosenListener.dragLeave(event);
  56         }
  57
  58         /* non Java-doc
  59          * @see DropTargetListener
  60          */
  61         public void dragOperationChanged(DropTargetEvent event){
  62                 if (fChosenListener != null)
  63                         fChosenListener.dragOperationChanged(event);
  64         }
  65
  66         /* non Java-doc
  67          * @see DropTargetListener
  68          */
  69         public void dragOver(DropTargetEvent event){
  70                 if (fChosenListener != null)
  71                         fChosenListener.dragOver(event);
  72         }
  73
  74         /* non Java-doc
  75          * @see DropTargetListener
  76          */
  77         public void drop(DropTargetEvent event){
  78                 if (fChosenListener != null)
  79                         fChosenListener.drop(event);
  80                 fChosenListener= null;
  81         }
  82
  83         /* non Java-doc
  84          * @see DropTargetListener
  85          */
  86         public void dropAccept(DropTargetEvent event){
  87                 if (fChosenListener != null)
  88                         fChosenListener.dropAccept(event);
  89         }
  90
  91         private TransferData selectPreferredListener(TransferData[] dataTypes) {
  92                 for (int i= 0; i < fListeners.length; i++) {
  93                         TransferData data= computeTransferData(dataTypes, fListeners[i]);
  94                         if (data != null)
  95                                 return data;
  96                 }
  97                 return null;
  98         }
  99
 100         private TransferData computeTransferData(TransferData[] dataTypes, TransferDropTargetListener listener) {
 101                 for (int i= 0; i < dataTypes.length; i++) {
 102                         if (listener.getTransfer().isSupportedType(dataTypes[i])) {
 103                                 fChosenListener= listener;
 104                                 return dataTypes[i];
 105                         }
 106                 }
 107                 return null;
 108         }
 109 }