NavigatorContentServiceTransfer


1   /*******************************************************************************
2    * Copyright (c) 2006 IBM Corporation and others.
3    * All rights reserved. This program and the accompanying materials
4    * are made available under the terms of the Eclipse Public License v1.0
5    * which accompanies this distribution, and is available at
6    * http://www.eclipse.org/legal/epl-v10.html
7    *
8    * Contributors:
9    *     IBM Corporation - initial API and implementation
10   ******************************************************************************/
11  
12  package org.eclipse.ui.internal.navigator.dnd;
13  
14  import java.lang.ref.WeakReference  ;
15  import java.util.HashSet  ;
16  import java.util.Iterator  ;
17  import java.util.Set  ;
18  
19  import org.eclipse.ui.navigator.INavigatorContentService;
20  
21  /**
22   * Caches instances of {@link INavigatorContentService} to facilitate the
23   * handling of drop operations in other viewers.
24   * 
25   * @since 3.2
26   * 
27   */
28  public class NavigatorContentServiceTransfer {
29      
30      private static final NavigatorContentServiceTransfer instance = new NavigatorContentServiceTransfer(); 
31      
32      /**
33       * 
34       * @return The singleton instance of the transfer service.
35       */
36      public static NavigatorContentServiceTransfer getInstance() {
37          return instance;
38      }
39  
40      private final Set   registeredContentServices = new HashSet  ();
41      
42      /**
43       *  
44       * @param aContentService The Content Service to register.
45       */
46      public synchronized void registerContentService(INavigatorContentService aContentService) { 
47          if(findService(aContentService.getViewerId()) == null) {
48              registeredContentServices.add(new WeakReference  (aContentService));
49          }
50      }
51      
52      /**
53       *  
54       * @param aContentService The Content Service to unregister.
55       */
56      public synchronized void unregisterContentService(INavigatorContentService aContentService) { 
57    
58          for (Iterator   iter = registeredContentServices.iterator(); iter.hasNext();) {
59              WeakReference   ref = (WeakReference  ) iter.next();
60              if(ref.get() == null) {
61                  iter.remove();
62              } else { 
63                  if(ref.get() == aContentService) {
64                      iter.remove(); 
65                      return;
66                  }
67              }
68          } 
69      }
70      
71      /**
72       * 
73       * @param aViewerId A viewer id that should have previously been registered with the service.
74       * @return The registered content service for the given viewer id.
75       */
76      public synchronized INavigatorContentService findService(String   aViewerId) {
77          if(aViewerId == null || aViewerId.length() == 0) {
78              return null;
79          }
80          INavigatorContentService contentService;
81          for (Iterator   iter = registeredContentServices.iterator(); iter.hasNext();) {
82              WeakReference   ref = (WeakReference  ) iter.next();
83              if(ref.get() == null) {
84                  iter.remove();
85              } else {
86                  contentService = (INavigatorContentService)ref.get();
87                  if(aViewerId.equals(contentService.getViewerId())) {
88                      return contentService;
89                  } 
90              }
91          }
92          return null;
93      } 
94      
95  
96  }
97
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