RetargetAction


1   /*******************************************************************************
2    * Copyright (c) 2000, 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  package org.eclipse.ui.actions;
12  
13  import org.eclipse.core.commands.IHandlerAttributes;
14  import org.eclipse.jface.action.IAction;
15  import org.eclipse.jface.util.IPropertyChangeListener;
16  import org.eclipse.jface.util.PropertyChangeEvent;
17  import org.eclipse.swt.events.HelpEvent;
18  import org.eclipse.swt.events.HelpListener;
19  import org.eclipse.swt.widgets.Event;
20  import org.eclipse.ui.IActionBars;
21  import org.eclipse.ui.IWorkbenchPart;
22  import org.eclipse.ui.IWorkbenchPartSite;
23  import org.eclipse.ui.SubActionBars;
24  import org.eclipse.ui.internal.PartSite;
25  
26  /**
27   * A <code>RetargetAction</code> tracks the active part in the workbench.  
28   * Each RetargetAction has an ID.  If the active part provides an action 
29   * handler for the ID the enable and check state of the RetargetAction
30   * is determined from the enable and check state of the handler.  If the 
31   * active part does not provide an action handler then this action is 
32   * disabled.
33   * </p>
34   * <p>
35   * <b>Note:</b> instances of this class add themselves as listeners to their
36   * action handler. It is important for the creator of a retarget action to call
37   * dispose when the action is no longer needed. This will ensure that the 
38   * listener is removed.
39   * </p>
40   * <p>
41   * This class may be instantiated. It is not intented to be subclassed.
42   * </p>
43   *
44   * @since 2.0 
45   */
46  public class RetargetAction extends PartEventAction implements
47          ActionFactory.IWorkbenchAction {
48  
49      /**
50       * The help listener assigned to this action, or <code>null</code> if none.
51       */
52      private HelpListener localHelpListener;
53  
54      private boolean enableAccelerator = true;
55  
56      private IAction handler;
57  
58      private IPropertyChangeListener propertyChangeListener = new IPropertyChangeListener() {
59          public void propertyChange(PropertyChangeEvent event) {
60              RetargetAction.this.propagateChange(event);
61          }
62      };
63  
64      /**
65       * Constructs a RetargetAction with the given action id and text.
66       * 
67       * @param actionID the retargetable action id
68       * @param text the action's text, or <code>null</code> if there is no text
69       */
70      public RetargetAction(String   actionID, String   text) {
71          this(actionID, text, IAction.AS_UNSPECIFIED);
72      }
73  
74      /**
75       * Constructs a RetargetAction with the given action id, text and style.
76       * 
77       * @param actionID the retargetable action id
78       * @param text the action's text, or <code>null</code> if there is no text
79       * @param style one of <code>AS_PUSH_BUTTON</code>, <code>AS_CHECK_BOX</code>,
80       *      <code>AS_DROP_DOWN_MENU</code>, <code>AS_RADIO_BUTTON</code>, and
81       *      <code>AS_UNSPECIFIED</code>
82       * @since 3.0
83       */
84      public RetargetAction(String   actionID, String   text, int style) {
85          super(text, style);
86          setId(actionID);
87          setEnabled(false);
88          super.setHelpListener(new HelpListener() {
89              public void helpRequested(HelpEvent e) {
90                  HelpListener listener = null;
91                  if (handler != null) {
92                      // if we have a handler, see if it has a help listener
93                      listener = handler.getHelpListener();
94                      if (listener == null) {
95                          // use our own help listener
96                          listener = localHelpListener;
97                      }
98                  }
99                  if (listener != null) {
100                     // pass on the event
101                     listener.helpRequested(e);
102                 }
103             }
104         });
105     }
106 
107     /**
108      * Disposes of the action and any resources held.
109      */
110     public void dispose() {
111         if (handler != null) {
112             handler.removePropertyChangeListener(propertyChangeListener);
113             handler = null;
114         }
115         IWorkbenchPart part = getActivePart();
116         if (part != null) {
117             IWorkbenchPartSite site = part.getSite();
118             SubActionBars bars = (SubActionBars) ((PartSite) site).getActionBars();
119             bars.removePropertyChangeListener(propertyChangeListener);
120         }
121     }
122 
123     /**
124      * Enables the accelerator for this action. 
125      *
126      * @param b the new enable state
127      */
128     public void enableAccelerator(boolean b) {
129         enableAccelerator = b;
130     }
131 
132     /* (non-Javadoc)
133      * Retaget actions do not have accelerators.  It is up to the
134      * part to hook the accelerator.
135      */
136     public int getAccelerator() {
137         if (enableAccelerator) {
138             return super.getAccelerator();
139         }
140         return 0;
141     }
142 
143     /**
144      * A workbench part has been activated. Try to connect
145      * to it.
146      *
147      * @param part the workbench part that has been activated
148      */
149     public void partActivated(IWorkbenchPart part) {
150         super.partActivated(part);
151         IWorkbenchPartSite site = part.getSite();
152         SubActionBars bars = (SubActionBars) ((PartSite) site).getActionBars();
153         bars.addPropertyChangeListener(propertyChangeListener);
154         setActionHandler(bars.getGlobalActionHandler(getId()));
155     }
156 
157     /**
158      * A workbench part has been closed. 
159      *
160      * @param part the workbench part that has been closed
161      */
162     public void partClosed(IWorkbenchPart part) {
163         IWorkbenchPart activePart = part.getSite().getPage().getActivePart();
164         if (activePart != null) {
165             // We are going to get a part activated message so don't bother setting the 
166             // action handler to null. This prevents enablement flash in the toolbar
167             return;
168         }
169         if (part == getActivePart()) {
170             setActionHandler(null);
171         }
172         super.partClosed(part);
173     }
174 
175     /**
176      * A workbench part has been deactivated. Disconnect from it.
177      *
178      * @param part the workbench part that has been deactivated
179      */
180     public void partDeactivated(IWorkbenchPart part) {
181         super.partDeactivated(part);
182         IWorkbenchPartSite site = part.getSite();
183         SubActionBars bars = (SubActionBars) ((PartSite) site).getActionBars();
184         bars.removePropertyChangeListener(propertyChangeListener);
185 
186         IWorkbenchPart activePart = part.getSite().getPage().getActivePart();
187         if (activePart != null) {
188             // We are going to get a part activated message so don't bother setting the 
189             // action handler to null. This prevents enablement flash in the toolbar
190             return;
191         }
192 
193         setActionHandler(null);
194     }
195 
196     /**
197      * Either the action handler itself has changed, or the configured action
198      * handlers on the action bars have changed. Update self.
199      */
200     protected void propagateChange(PropertyChangeEvent event) {
201         if (event.getProperty().equals(IAction.ENABLED)) {
202             Boolean   bool = (Boolean  ) event.getNewValue();
203             setEnabled(bool.booleanValue());
204         } else if (event.getProperty().equals(IAction.CHECKED)) {
205             Boolean   bool = (Boolean  ) event.getNewValue();
206             setChecked(bool.booleanValue());
207         } else if (event.getProperty().equals(SubActionBars.P_ACTION_HANDLERS)) {
208             if (event.getSource() instanceof IActionBars) {
209                 IActionBars bars = (IActionBars) event.getSource();
210                 setActionHandler(bars.getGlobalActionHandler(getId()));
211             }
212         }
213     }
214 
215     /**
216      * Invoked when an action occurs. 
217      */
218     public void run() {
219         if (handler != null) {
220             handler.run();
221         }
222     }
223 
224     /**
225      * Invoked when an action occurs. 
226      */
227     public void runWithEvent(Event event) {
228         if (handler != null) {
229             handler.runWithEvent(event);
230         }
231     }
232 
233     /**
234      * Returns the action handler. This method was made public in 3.0.
235      * 
236      * @return The current action handling this retargettable action. This
237      *         handler will be <code>null</code> if there is no current
238      *         handler.
239      */
240     public IAction getActionHandler() {
241         return handler;
242     }
243     
244     public final boolean isHandled() {
245         return (handler != null);
246     }
247 
248     /**
249      * Sets the action handler.
250      */
251     protected void setActionHandler(IAction newHandler) {
252         // Optimize.
253         if (newHandler == handler) {
254             return;
255         }
256 
257         // Clear old action.
258         if (handler != null) {
259             handler.removePropertyChangeListener(propertyChangeListener);
260             handler = null;
261         }
262 
263         // Set new action.
264         IAction oldHandler = handler;
265         handler = newHandler;
266         if (handler == null) {
267             setEnabled(false);
268             if (getStyle() == AS_CHECK_BOX || getStyle() == AS_RADIO_BUTTON) {
269                 setChecked(false);
270             }
271         } else {
272             setEnabled(handler.isEnabled());
273             if (getStyle() == AS_CHECK_BOX || getStyle() == AS_RADIO_BUTTON) {
274                 setChecked(handler.isChecked());
275             }
276             handler.addPropertyChangeListener(propertyChangeListener);
277         }
278         
279         // Notify listeners that the handler has changed.
280         firePropertyChange(IHandlerAttributes.ATTRIBUTE_HANDLED, oldHandler,
281                 newHandler);
282     }
283 
284     /* (non-Javadoc)
285      * Method declared on IAction.
286      */
287     public void setChecked(boolean checked) {
288         super.setChecked(checked);
289         // This call may come from the SWT control event handler
290         // itself, so notify the handler action to keep things
291         // in sync.
292         if (handler != null) {
293             handler.setChecked(checked);
294         }
295     }
296 
297     /** 
298      * The <code>RetargetAction</code> implementation of this method declared on
299      * <code>IAction</code> stores the help listener in a local field. The
300      * supplied listener is only used if there is no hanlder.
301      */
302     public void setHelpListener(HelpListener listener) {
303         localHelpListener = listener;
304     }
305 
306     /**
307      * Returns a string representation of this action.
308      * 
309      * @return A string representation of this action.
310      * 
311      * @since 3.2 
312      */
313     public final String   toString() {
314         final StringBuffer   buffer = new StringBuffer  ();
315 
316         buffer.append("RetargetAction("); //$NON-NLS-1$
317         buffer.append(getId());
318         buffer.append(')');
319 
320         return buffer.toString();
321     }
322 }
323
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