/*
* Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package javax.swing.undo;
import java.io.Serializable;
import javax.swing.UIManager;
/**
* An abstract implementation of UndoableEdit
,
* implementing simple responses to all boolean methods in
* that interface.
*
* @author Ray Ryan
*/
@SuppressWarnings("serial") // Same-version serialization only
public class AbstractUndoableEdit implements UndoableEdit, Serializable {
/**
* String returned by getUndoPresentationName
;
* 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
* AbstractUndoableEdit.undoText
.
*
* @see javax.swing.UIDefaults
*/
protected static final String UndoName = "Undo";
/**
* String returned by getRedoPresentationName
;
* 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
* AbstractUndoableEdit.redoText
.
*
* @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 die
; defaults
* to true
.
*/
boolean alive;
/**
* Creates an AbstractUndoableEdit
which defaults
* hasBeenDone
and alive
to true
.
*/
public AbstractUndoableEdit() {
super();
hasBeenDone = true;
alive = true;
}
/**
* Sets alive
to false. Note that this
* is a one way operation; dead edits cannot be resurrected.
* Sending undo
or redo
to
* a dead edit results in an exception being thrown.
*
*
Typically an edit is killed when it is consolidated by
* another edit's addEdit
or replaceEdit
* method, or when it is dequeued from an UndoManager
.
*/
public void die() {
alive = false;
}
/**
* Throws CannotUndoException
if canUndo
* returns false
. Sets hasBeenDone
* to false
. Subclasses should override to undo the
* operation represented by this edit. Override should begin with
* a call to super.
*
* @exception CannotUndoException if canUndo
* returns false
* @see #canUndo
*/
public void undo() throws CannotUndoException {
if (!canUndo()) {
throw new CannotUndoException();
}
hasBeenDone = false;
}
/**
* Returns true if this edit is alive
* and hasBeenDone
is true
.
*
* @return true if this edit is alive
* and hasBeenDone
is true
*
* @see #die
* @see #undo
* @see #redo
*/
public boolean canUndo() {
return alive && hasBeenDone;
}
/**
* Throws CannotRedoException
if canRedo
* returns false. Sets hasBeenDone
to true
.
* Subclasses should override to redo the operation represented by
* this edit. Override should begin with a call to super.
*
* @exception CannotRedoException if canRedo
* returns false
* @see #canRedo
*/
public void redo() throws CannotRedoException {
if (!canRedo()) {
throw new CannotRedoException();
}
hasBeenDone = true;
}
/**
* Returns true
if this edit is alive
* and hasBeenDone
is false
.
*
* @return true
if this edit is alive
* and hasBeenDone
is false
* @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
* getUndoPresentationName
and
* getRedoPresentationName
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
* AbstractUndoableEdit.undoText
and returns
* that value followed by a space, followed by
* getPresentationName
.
* If getPresentationName
returns "",
* then the defaults value is returned alone.
*
* @return the value from the defaults table with key
* AbstractUndoableEdit.undoText
, followed
* by a space, followed by getPresentationName
* unless getPresentationName
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
* AbstractUndoableEdit.redoText
and returns
* that value followed by a space, followed by
* getPresentationName
.
* If getPresentationName
returns "",
* then the defaults value is returned alone.
*
* @return the value from the defaults table with key
* AbstractUndoableEdit.redoText
, followed
* by a space, followed by getPresentationName
* unless getPresentationName
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;
}
}