/*
* Copyright (c) 1997, 2006, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
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*/
package javax.swing.undo;
import java.io.Serializable;
import javax.swing.UIManager;
/**
* An abstract implementation of <code>UndoableEdit</code>,
* implementing simple responses to all boolean methods in
* that interface.
*
* @author Ray Ryan
*/
public class AbstractUndoableEdit implements UndoableEdit, Serializable {
/**
* String returned by <code>getUndoPresentationName</code>;
* as of Java 2 platform v1.3.1 this field is no longer used. This value
* is now localized and comes from the defaults table with key
* <code>AbstractUndoableEdit.undoText</code>.
*
* @see javax.swing.UIDefaults
*/
protected static final String UndoName = "Undo";
/**
* String returned by <code>getRedoPresentationName</code>;
* as of Java 2 platform v1.3.1 this field is no longer used. This value
* is now localized and comes from the defaults table with key
* <code>AbstractUndoableEdit.redoText</code>.
*
* @see javax.swing.UIDefaults
*/
protected static final String RedoName = "Redo";
/**
* Defaults to true; becomes false if this edit is undone, true
* again if it is redone.
*/
boolean hasBeenDone;
/**
* True if this edit has not received <code>die</code>; defaults
* to <code>true</code>.
*/
boolean alive;
/**
* Creates an <code>AbstractUndoableEdit</code> which defaults
* <code>hasBeenDone</code> and <code>alive</code> to <code>true</code>.
*/
public AbstractUndoableEdit() {
super();
hasBeenDone = true;
alive = true;
}
/**
* Sets <code>alive</code> to false. Note that this
* is a one way operation; dead edits cannot be resurrected.
* Sending <code>undo</code> or <code>redo</code> to
* a dead edit results in an exception being thrown.
*
* <p>Typically an edit is killed when it is consolidated by
* another edit's <code>addEdit</code> or <code>replaceEdit</code>
* method, or when it is dequeued from an <code>UndoManager</code>.
*/
public void die() {
alive = false;
}
/**
* Throws <code>CannotUndoException</code> if <code>canUndo</code>
* returns <code>false</code>. Sets <code>hasBeenDone</code>
* to <code>false</code>. Subclasses should override to undo the
* operation represented by this edit. Override should begin with
* a call to super.
*
* @exception CannotUndoException if <code>canUndo</code>
* returns <code>false</code>
* @see #canUndo
*/
public void undo() throws CannotUndoException {
if (!canUndo()) {
throw new CannotUndoException();
}
hasBeenDone = false;
}
/**
* Returns true if this edit is <code>alive</code>
* and <code>hasBeenDone</code> is <code>true</code>.
*
* @return true if this edit is <code>alive</code>
* and <code>hasBeenDone</code> is <code>true</code>
*
* @see #die
* @see #undo
* @see #redo
*/
public boolean canUndo() {
return alive && hasBeenDone;
}
/**
* Throws <code>CannotRedoException</code> if <code>canRedo</code>
* returns false. Sets <code>hasBeenDone</code> to <code>true</code>.
* Subclasses should override to redo the operation represented by
* this edit. Override should begin with a call to super.
*
* @exception CannotRedoException if <code>canRedo</code>
* returns <code>false</code>
* @see #canRedo
*/
public void redo() throws CannotRedoException {
if (!canRedo()) {
throw new CannotRedoException();
}
hasBeenDone = true;
}
/**
* Returns <code>true</code> if this edit is <code>alive</code>
* and <code>hasBeenDone</code> is <code>false</code>.
*
* @return <code>true</code> if this edit is <code>alive</code>
* and <code>hasBeenDone</code> is <code>false</code>
* @see #die
* @see #undo
* @see #redo
*/
public boolean canRedo() {
return alive && !hasBeenDone;
}
/**
* This default implementation returns false.
*
* @param anEdit the edit to be added
* @return false
*
* @see UndoableEdit#addEdit
*/
public boolean addEdit(UndoableEdit anEdit) {
return false;
}
/**
* This default implementation returns false.
*
* @param anEdit the edit to replace
* @return false
*
* @see UndoableEdit#replaceEdit
*/
public boolean replaceEdit(UndoableEdit anEdit) {
return false;
}
/**
* This default implementation returns true.
*
* @return true
* @see UndoableEdit#isSignificant
*/
public boolean isSignificant() {
return true;
}
/**
* This default implementation returns "". Used by
* <code>getUndoPresentationName</code> and
* <code>getRedoPresentationName</code> to
* construct the strings they return. Subclasses should override to
* return an appropriate description of the operation this edit
* represents.
*
* @return the empty string ""
*
* @see #getUndoPresentationName
* @see #getRedoPresentationName
*/
public String getPresentationName() {
return "";
}
/**
* Retreives the value from the defaults table with key
* <code>AbstractUndoableEdit.undoText</code> and returns
* that value followed by a space, followed by
* <code>getPresentationName</code>.
* If <code>getPresentationName</code> returns "",
* then the defaults value is returned alone.
*
* @return the value from the defaults table with key
* <code>AbstractUndoableEdit.undoText</code>, followed
* by a space, followed by <code>getPresentationName</code>
* unless <code>getPresentationName</code> is "" in which
* case, the defaults value is returned alone.
* @see #getPresentationName
*/
public String getUndoPresentationName() {
String name = getPresentationName();
if (!"".equals(name)) {
name = UIManager.getString("AbstractUndoableEdit.undoText") +
" " + name;
} else {
name = UIManager.getString("AbstractUndoableEdit.undoText");
}
return name;
}
/**
* Retreives the value from the defaults table with key
* <code>AbstractUndoableEdit.redoText</code> and returns
* that value followed by a space, followed by
* <code>getPresentationName</code>.
* If <code>getPresentationName</code> returns "",
* then the defaults value is returned alone.
*
* @return the value from the defaults table with key
* <code>AbstractUndoableEdit.redoText</code>, followed
* by a space, followed by <code>getPresentationName</code>
* unless <code>getPresentationName</code> is "" in which
* case, the defaults value is returned alone.
* @see #getPresentationName
*/
public String getRedoPresentationName() {
String name = getPresentationName();
if (!"".equals(name)) {
name = UIManager.getString("AbstractUndoableEdit.redoText") +
" " + name;
} else {
name = UIManager.getString("AbstractUndoableEdit.redoText");
}
return name;
}
/**
* Returns a string that displays and identifies this
* object's properties.
*
* @return a String representation of this object
*/
public String toString()
{
return super.toString()
+ " hasBeenDone: " + hasBeenDone
+ " alive: " + alive;
}
}