public class

UndoManager

extends CompoundEdit
implements UndoableEditListener
java.lang.Object
   ↳ javax.swing.undo.AbstractUndoableEdit
     ↳ javax.swing.undo.CompoundEdit
       ↳ javax.swing.undo.UndoManager

Class Overview

UndoManager manages a list of UndoableEdits, providing a way to undo or redo the appropriate edits. There are two ways to add edits to an UndoManager. Add the edit directly using the addEdit method, or add the UndoManager to a bean that supports UndoableEditListener. The following examples creates an UndoManager and adds it as an UndoableEditListener to a JTextField: 

   UndoManager undoManager = new UndoManager();
   JTextField tf = ...;
   tf.getDocument().addUndoableEditListener(undoManager);

UndoManager maintains an ordered list of edits and the index of the next edit in that list. The index of the next edit is either the size of the current list of edits, or if undo has been invoked it corresponds to the index of the last significant edit that was undone. When undo is invoked all edits from the index of the next edit to the last significant edit are undone, in reverse order. For example, consider an UndoManager consisting of the following edits: A b c D. Edits with a upper-case letter in bold are significant, those in lower-case and italicized are insignificant.

Figure 1

As shown in figure 1, if D was just added, the index of the next edit will be 4. Invoking undo results in invoking undo on D and setting the index of the next edit to 3 (edit c), as shown in the following figure.

Figure 2

The last significant edit is A, so that invoking undo again invokes undo on c, b, and A, in that order, setting the index of the next edit to 0, as shown in the following figure.

Figure 3

Invoking redo results in invoking redo on all edits between the index of the next edit and the next significant edit (or the end of the list). Continuing with the previous example if redo were invoked, redo would in turn be invoked on A, b and c. In addition the index of the next edit is set to 3 (as shown in figure 2).

Adding an edit to an UndoManager results in removing all edits from the index of the next edit to the end of the list. Continuing with the previous example, if a new edit, e, is added the edit D is removed from the list (after having die invoked on it). If c is not incorporated by the next edit (c.addEdit(e) returns true), or replaced by it (e.replaceEdit(c) returns true), the new edit is added after c, as shown in the following figure.

Figure 4

Once end has been invoked on an UndoManager the superclass behavior is used for all UndoableEdit methods. Refer to CompoundEdit for more details on its behavior.

Unlike the rest of Swing, this class is thread safe.

Warning: Serialized objects of this class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. As of 1.4, support for long term storage of all JavaBeansTM has been added to the java.beans package. Please see XMLEncoder.

Summary

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Inherited Constants
From class javax.swing.undo.AbstractUndoableEdit
[Expand]
Inherited Fields
From class javax.swing.undo.CompoundEdit
Public Constructors
UndoManager()
Creates a new UndoManager.
Public Methods
synchronized boolean addEdit(UndoableEdit anEdit)
Adds an UndoableEdit to this UndoManager, if it's possible.
synchronized boolean canRedo()
Returns true if edits may be redone.
synchronized boolean canUndo()
Returns true if edits may be undone.
synchronized boolean canUndoOrRedo()
Returns true if it is possible to invoke undo or redo.
synchronized void discardAllEdits()
Empties the undo manager sending each edit a die message in the process.
synchronized void end()
Turns this UndoManager into a normal CompoundEdit.
synchronized int getLimit()
Returns the maximum number of edits this UndoManager holds.
synchronized String getRedoPresentationName()
Returns a description of the redoable form of this edit.
synchronized String getUndoOrRedoPresentationName()
Convenience method that returns either getUndoPresentationName or getRedoPresentationName.
synchronized String getUndoPresentationName()
Returns a description of the undoable form of this edit.
synchronized void redo()
Redoes the appropriate edits.
synchronized void setLimit(int l)
Sets the maximum number of edits this UndoManager holds.
String toString()
Returns a string that displays and identifies this object's properties.
synchronized void undo()
Undoes the appropriate edits.
synchronized void undoOrRedo()
Convenience method that invokes one of undo or redo.
void undoableEditHappened(UndoableEditEvent e)
An UndoableEditListener method.
Protected Methods
UndoableEdit editToBeRedone()
Returns the the next significant edit to be redone if redo is invoked.
UndoableEdit editToBeUndone()
Returns the the next significant edit to be undone if undo is invoked.
void redoTo(UndoableEdit edit)
Redoes all changes from the index of the next edit to edit, updating the index of the next edit appropriately.
void trimEdits(int from, int to)
Removes edits in the specified range.
void trimForLimit()
Reduces the number of queued edits to a range of size limit, centered on the index of the next edit.
void undoTo(UndoableEdit edit)
Undoes all changes from the index of the next edit to edit, updating the index of the next edit appropriately.
[Expand]
Inherited Methods
From class javax.swing.undo.CompoundEdit
From class javax.swing.undo.AbstractUndoableEdit
From class java.lang.Object
From interface javax.swing.event.UndoableEditListener
From interface javax.swing.undo.UndoableEdit

Public Constructors

public UndoManager ()

Creates a new UndoManager.

Public Methods

public synchronized boolean addEdit (UndoableEdit anEdit)

Adds an UndoableEdit to this UndoManager, if it's possible. This removes all edits from the index of the next edit to the end of the edits list. If end has been invoked the edit is not added and false is returned. If end hasn't been invoked this returns true.

Parameters
anEdit the edit to be added
Returns
  • true if anEdit can be incorporated into this edit
See Also

public synchronized boolean canRedo ()

Returns true if edits may be redone. If end has been invoked, this returns the value from super. Otherwise, this returns true if there are any edits to be redone (editToBeRedone returns non-null).

Returns
  • true if there are edits to be redone
See Also

public synchronized boolean canUndo ()

Returns true if edits may be undone. If end has been invoked, this returns the value from super. Otherwise this returns true if there are any edits to be undone (editToBeUndone returns non-null).

Returns
  • true if there are edits to be undone
See Also

public synchronized boolean canUndoOrRedo ()

Returns true if it is possible to invoke undo or redo.

Returns
  • true if invoking canUndoOrRedo is valid
See Also

public synchronized void discardAllEdits ()

Empties the undo manager sending each edit a die message in the process.

See Also

public synchronized void end ()

Turns this UndoManager into a normal CompoundEdit. This removes all edits that have been undone.

See Also

public synchronized int getLimit ()

Returns the maximum number of edits this UndoManager holds. A value less than 0 indicates the number of edits is not limited.

Returns
  • the maximum number of edits this UndoManager holds
See Also

public synchronized String getRedoPresentationName ()

Returns a description of the redoable form of this edit. If end has been invoked this calls into super. Otherwise if there are edits to be redone, this returns the value from the next significant edit that will be redone. If there are no edits to be redone and end has not been invoked this returns the value from the UIManager property "AbstractUndoableEdit.redoText".

Returns
  • a description of the redoable form of this edit
See Also

public synchronized String getUndoOrRedoPresentationName ()

Convenience method that returns either getUndoPresentationName or getRedoPresentationName. If the index of the next edit equals the size of the edits list, getUndoPresentationName is returned, otherwise getRedoPresentationName is returned.

Returns
  • undo or redo name

public synchronized String getUndoPresentationName ()

Returns a description of the undoable form of this edit. If end has been invoked this calls into super. Otherwise if there are edits to be undone, this returns the value from the next significant edit that will be undone. If there are no edits to be undone and end has not been invoked this returns the value from the UIManager property "AbstractUndoableEdit.undoText".

Returns
  • a description of the undoable form of this edit
See Also

public synchronized void redo ()

Redoes the appropriate edits. If end has been invoked this calls through to the superclass. Otherwise this invokes redo on all edits between the index of the next edit and the next significant edit, updating the index of the next edit appropriately.

Throws
CannotRedoException if one of the edits throws CannotRedoException or there are no edits to be redone
See Also

public synchronized void setLimit (int l)

Sets the maximum number of edits this UndoManager holds. A value less than 0 indicates the number of edits is not limited. If edits need to be discarded to shrink the limit, die will be invoked on them in the reverse order they were added. The default is 100.

Parameters
l the new limit
Throws
RuntimeException if this UndoManager is not in progress (end has been invoked)
See Also

public String toString ()

Returns a string that displays and identifies this object's properties.

Returns
  • a String representation of this object

public synchronized void undo ()

Undoes the appropriate edits. If end has been invoked this calls through to the superclass, otherwise this invokes undo on all edits between the index of the next edit and the last significant edit, updating the index of the next edit appropriately.

Throws
CannotUndoException if one of the edits throws CannotUndoException or there are no edits to be undone
See Also

public synchronized void undoOrRedo ()

Convenience method that invokes one of undo or redo. If any edits have been undone (the index of the next edit is less than the length of the edits list) this invokes redo, otherwise it invokes undo.

Throws
CannotUndoException if one of the edits throws CannotUndoException
CannotRedoException if one of the edits throws CannotRedoException
See Also

public void undoableEditHappened (UndoableEditEvent e)

An UndoableEditListener method. This invokes addEdit with e.getEdit().

Parameters
e the UndoableEditEvent the UndoableEditEvent will be added from
See Also

Protected Methods

protected UndoableEdit editToBeRedone ()

Returns the the next significant edit to be redone if redo is invoked. This returns null if there are no edits to be redone.

Returns
  • the next significant edit to be redone

protected UndoableEdit editToBeUndone ()

Returns the the next significant edit to be undone if undo is invoked. This returns null if there are no edits to be undone.

Returns
  • the next significant edit to be undone

protected void redoTo (UndoableEdit edit)

Redoes all changes from the index of the next edit to edit, updating the index of the next edit appropriately.

Throws
CannotRedoException if one of the edits throws CannotRedoException

protected void trimEdits (int from, int to)

Removes edits in the specified range. All edits in the given range (inclusive, and in reverse order) will have die invoked on them and are removed from the list of edits. This has no effect if from > to.

Parameters
from the minimum index to remove
to the maximum index to remove

protected void trimForLimit ()

Reduces the number of queued edits to a range of size limit, centered on the index of the next edit.

protected void undoTo (UndoableEdit edit)

Undoes all changes from the index of the next edit to edit, updating the index of the next edit appropriately.

Throws
CannotUndoException if one of the edits throws CannotUndoException