AbstractUndoableEdit


1   /*
2    * @(#)AbstractUndoableEdit.java    1.29 03/12/19
3    *
4    * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6    */
7   
8   package javax.swing.undo;
9   
10  import java.io.Serializable  ;
11  import javax.swing.UIManager  ;
12  
13  /**
14   * An abstract implementation of <code>UndoableEdit</code>,
15   * implementing simple responses to all boolean methods in
16   * that interface. 
17   *
18   * @version 1.29 12/19/03
19   * @author Ray Ryan
20   */
21  public class AbstractUndoableEdit implements UndoableEdit  , Serializable   {
22  
23      /**
24       * String returned by <code>getUndoPresentationName</code>;
25       * as of Java 2 platform v1.3.1 this field is no longer used. This value
26       * is now localized and comes from the defaults table with key
27       * <code>AbstractUndoableEdit.undoText</code>.
28       *
29       * @see javax.swing.UIDefaults
30       */
31      protected static final String   UndoName = "Undo";
32  
33      /**
34       * String returned by <code>getRedoPresentationName</code>;
35       * as of Java 2 platform v1.3.1 this field is no longer used. This value
36       * is now localized and comes from the defaults table with key
37       * <code>AbstractUndoableEdit.redoText</code>.
38       *
39       * @see javax.swing.UIDefaults
40       */
41      protected static final String   RedoName = "Redo";
42  
43      /**
44       * Defaults to true; becomes false if this edit is undone, true
45       * again if it is redone.  
46       */
47      boolean hasBeenDone;
48  
49      /**
50       * True if this edit has not received <code>die</code>; defaults
51       * to <code>true</code>.
52       */
53      boolean alive;
54  
55      /**
56       * Creates an <code>AbstractUndoableEdit</code> which defaults
57       * <code.hasBeenDone</code> and <code>alive</code> to <code>true</code>.
58       */
59      public AbstractUndoableEdit() {
60      super();
61  
62      hasBeenDone = true;
63      alive = true;
64      }
65  
66      /**
67       * Sets <code>alive</code> to false. Note that this
68       * is a one way operation; dead edits cannot be resurrected.
69       * Sending <code>undo</code> or <code>redo</code> to
70       * a dead edit results in an exception being thrown.
71       *
72       * <p>Typically an edit is killed when it is consolidated by 
73       * another edit's <code>addEdit</code> or <code>replaceEdit</code>
74       * method, or when it is dequeued from an <code>UndoManager</code>.
75       */
76      public void die() {
77      alive = false;
78      }
79  
80      /**
81       * Throws <code>CannotUndoException</code> if <code>canUndo</code>
82       * returns <code>false</code>. Sets <code>hasBeenDone</code>
83       * to <code>false</code>. Subclasses should override to undo the
84       * operation represented by this edit. Override should begin with
85       * a call to super.
86       *
87       * @exception CannotUndoException if <code>canUndo</code>
88       *    returns <code>false</code>
89       * @see #canUndo
90       */
91      public void undo() throws CannotUndoException   {
92      if (!canUndo()) {
93          throw new CannotUndoException  ();
94      }
95      hasBeenDone = false;
96      }
97  
98      /**
99       * Returns true if this edit is <code>alive</code>
100      * and <code>hasBeenDone</code> is <code>true</code>.
101      *
102      * @return true if this edit is <code>alive</code>
103      *    and <code>hasBeenDone</code> is <code>true</code>
104      *
105      * @see     #die
106      * @see #undo
107      * @see #redo
108      */
109     public boolean canUndo() {
110     return alive && hasBeenDone;
111     }
112 
113     /**
114      * Throws <code>CannotRedoException</code> if <code>canRedo</code>
115      * returns false. Sets <code>hasBeenDone</code> to <code>true</code>.
116      * Subclasses should override to redo the operation represented by
117      * this edit. Override should begin with a call to super.
118      *
119      * @exception CannotRedoException if <code>canRedo</code>
120      *     returns <code>false</code>
121      * @see #canRedo
122      */
123     public void redo() throws CannotRedoException   {
124     if (!canRedo()) {
125         throw new CannotRedoException  ();
126     }
127     hasBeenDone = true;
128     }
129 
130     /**
131      * Returns <code>true</code> if this edit is <code>alive</code>
132      * and <code>hasBeenDone</code> is <code>false</code>.
133      *
134      * @return <code>true</code> if this edit is <code>alive</code>
135      *   and <code>hasBeenDone</code> is <code>false</code>
136      * @see     #die
137      * @see #undo
138      * @see #redo
139      */
140     public boolean canRedo() {
141     return alive && !hasBeenDone;
142     }
143     
144     /**
145      * This default implementation returns false. 
146      *
147      * @param anEdit the edit to be added
148      * @return false
149      *
150      * @see UndoableEdit#addEdit
151      */
152     public boolean addEdit(UndoableEdit   anEdit) {
153     return false;
154     }
155 
156     /**
157      * This default implementation returns false. 
158      *
159      * @param anEdit the edit to replace
160      * @return false
161      *
162      * @see UndoableEdit#replaceEdit
163      */
164     public boolean replaceEdit(UndoableEdit   anEdit) {
165     return false;
166     }
167 
168     /**
169      * This default implementation returns true. 
170      *
171      * @return true
172      * @see UndoableEdit#isSignificant
173      */
174     public boolean isSignificant() {
175     return true;
176     }
177 
178     /**
179      * This default implementation returns "". Used by
180      * <code>getUndoPresentationName</code> and 
181      * <code>getRedoPresentationName</code> to
182      * construct the strings they return. Subclasses should override to
183      * return an appropriate description of the operation this edit
184      * represents.
185      *
186      * @return the empty string ""
187      *
188      * @see #getUndoPresentationName
189      * @see #getRedoPresentationName
190      */
191     public String   getPresentationName() {
192     return "";
193     }
194 
195     /**
196      * Retreives the value from the defaults table with key
197      * <code>AbstractUndoableEdit.undoText</code> and returns
198      * that value followed by a space, followed by
199      * <code>getPresentationName</code>.
200      * If <code>getPresentationName</code> returns "",
201      * then the defaults value is returned alone.
202      *
203      * @return the value from the defaults table with key
204      *    <code>AbstractUndoableEdit.undoText</code>, followed
205      *    by a space, followed by <code>getPresentationName</code>
206      *    unless <code>getPresentationName</code> is "" in which
207      *    case, the defaults value is returned alone.
208      * @see #getPresentationName
209      */
210     public String   getUndoPresentationName() {
211     String   name = getPresentationName();
212     if (!"".equals(name)) {
213         name = UIManager.getString("AbstractUndoableEdit.undoText") +
214                 " " + name;
215     } else {
216         name = UIManager.getString("AbstractUndoableEdit.undoText");
217     }
218 
219     return name;
220     }
221 
222     /**
223      * Retreives the value from the defaults table with key
224      * <code>AbstractUndoableEdit.redoText</code> and returns
225      * that value followed by a space, followed by
226      * <code>getPresentationName</code>.
227      * If <code>getPresentationName</code> returns "",
228      * then the defaults value is returned alone.
229      *
230      * @return the value from the defaults table with key
231      *    <code>AbstractUndoableEdit.redoText</code>, followed
232      *    by a space, followed by <code>getPresentationName</code>
233      *    unless <code>getPresentationName</code> is "" in which
234      *    case, the defaults value is returned alone.
235      * @see #getPresentationName
236      */
237     public String   getRedoPresentationName() {
238     String   name = getPresentationName();
239     if (!"".equals(name)) {
240         name = UIManager.getString("AbstractUndoableEdit.redoText") +
241                 " " + name;
242     } else {
243         name = UIManager.getString("AbstractUndoableEdit.redoText");
244     }
245 
246     return name;
247     }
248 
249     /**
250      * Returns a string that displays and identifies this
251      * object's properties.
252      *
253      * @return a String representation of this object
254      */
255     public String   toString()
256     {
257     return super.toString()
258         + " hasBeenDone: " + hasBeenDone
259         + " alive: " + alive;
260     }
261 }
262 
263
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