public class UndoManager extends CompoundEdit implements UndoableEditListener
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 JavaBeans™
has been added to the java.beans
package.
Please see XMLEncoder
.
edits
RedoName, UndoName
Constructor and Description |
---|
UndoManager()
Creates a new
UndoManager . |
Modifier and Type | Method and Description |
---|---|
boolean |
addEdit(UndoableEdit anEdit)
Adds an
UndoableEdit to this
UndoManager , if it's possible. |
boolean |
canRedo()
Returns true if edits may be redone.
|
boolean |
canUndo()
Returns true if edits may be undone.
|
boolean |
canUndoOrRedo()
Returns true if it is possible to invoke
undo or
redo . |
void |
discardAllEdits()
Empties the undo manager sending each edit a
die message
in the process. |
protected UndoableEdit |
editToBeRedone()
Returns the the next significant edit to be redone if
redo
is invoked. |
protected UndoableEdit |
editToBeUndone()
Returns the the next significant edit to be undone if
undo
is invoked. |
void |
end()
Turns this
UndoManager into a normal
CompoundEdit . |
int |
getLimit()
Returns the maximum number of edits this
UndoManager
holds. |
String |
getRedoPresentationName()
Returns a description of the redoable form of this edit.
|
String |
getUndoOrRedoPresentationName()
Convenience method that returns either
getUndoPresentationName or
getRedoPresentationName . |
String |
getUndoPresentationName()
Returns a description of the undoable form of this edit.
|
void |
redo()
Redoes the appropriate edits.
|
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. |
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.
|
protected void |
trimEdits(int from,
int to)
Removes edits in the specified range.
|
protected void |
trimForLimit()
Reduces the number of queued edits to a range of size limit,
centered on the index of the next edit.
|
void |
undo()
Undoes the appropriate edits.
|
void |
undoableEditHappened(UndoableEditEvent e)
An
UndoableEditListener method. |
void |
undoOrRedo()
Convenience method that invokes one of
undo or
redo . |
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. |
die, getPresentationName, isInProgress, isSignificant, lastEdit
replaceEdit
public int getLimit()
UndoManager
holds. A value less than 0 indicates the number of edits is not
limited.UndoManager
holdsaddEdit(javax.swing.undo.UndoableEdit)
,
setLimit(int)
public void discardAllEdits()
die
message
in the process.AbstractUndoableEdit.die()
protected void trimForLimit()
protected void trimEdits(int from, int to)
die
invoked on them and are removed from
the list of edits. This has no effect if
from
> to
.from
- the minimum index to removeto
- the maximum index to removepublic void setLimit(int l)
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.l
- the new limitRuntimeException
- if this UndoManager
is not in progress
(end
has been invoked)CompoundEdit.isInProgress()
,
end()
,
addEdit(javax.swing.undo.UndoableEdit)
,
getLimit()
protected UndoableEdit editToBeUndone()
undo
is invoked. This returns null
if there are no edits
to be undone.protected UndoableEdit editToBeRedone()
redo
is invoked. This returns null
if there are no edits
to be redone.protected void undoTo(UndoableEdit edit) throws CannotUndoException
edit
, updating the index of the next edit appropriately.CannotUndoException
- if one of the edits throws
CannotUndoException
protected void redoTo(UndoableEdit edit) throws CannotRedoException
edit
, updating the index of the next edit appropriately.CannotRedoException
- if one of the edits throws
CannotRedoException
public void undoOrRedo() throws CannotRedoException, CannotUndoException
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
.CannotUndoException
- if one of the edits throws
CannotUndoException
CannotRedoException
- if one of the edits throws
CannotRedoException
canUndoOrRedo()
,
getUndoOrRedoPresentationName()
public boolean canUndoOrRedo()
undo
or
redo
.canUndoOrRedo
is validundoOrRedo()
public void undo() throws CannotUndoException
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.undo
in interface UndoableEdit
undo
in class CompoundEdit
CannotUndoException
- if one of the edits throws
CannotUndoException
or there are no edits
to be undoneCompoundEdit.end()
,
canUndo()
,
editToBeUndone()
public boolean canUndo()
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
).canUndo
in interface UndoableEdit
canUndo
in class CompoundEdit
CompoundEdit.canUndo()
,
editToBeUndone()
public void redo() throws CannotRedoException
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.redo
in interface UndoableEdit
redo
in class CompoundEdit
CannotRedoException
- if one of the edits throws
CannotRedoException
or there are no edits
to be redoneCompoundEdit.end()
,
canRedo()
,
editToBeRedone()
public boolean canRedo()
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
).canRedo
in interface UndoableEdit
canRedo
in class CompoundEdit
CompoundEdit.canRedo()
,
editToBeRedone()
public boolean addEdit(UndoableEdit anEdit)
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
.addEdit
in interface UndoableEdit
addEdit
in class CompoundEdit
anEdit
- the edit to be addedanEdit
can be incorporated into this
editCompoundEdit.end()
,
CompoundEdit.addEdit(javax.swing.undo.UndoableEdit)
public void end()
UndoManager
into a normal
CompoundEdit
. This removes all edits that have
been undone.end
in class CompoundEdit
CompoundEdit.end()
public String getUndoOrRedoPresentationName()
getUndoPresentationName
or
getRedoPresentationName
. If the index of the next
edit equals the size of the edits list,
getUndoPresentationName
is returned, otherwise
getRedoPresentationName
is returned.public String getUndoPresentationName()
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".getUndoPresentationName
in interface UndoableEdit
getUndoPresentationName
in class CompoundEdit
undo()
,
CompoundEdit.getUndoPresentationName()
public String getRedoPresentationName()
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".getRedoPresentationName
in interface UndoableEdit
getRedoPresentationName
in class CompoundEdit
redo()
,
CompoundEdit.getRedoPresentationName()
public void undoableEditHappened(UndoableEditEvent e)
UndoableEditListener
method. This invokes
addEdit
with e.getEdit()
.undoableEditHappened
in interface UndoableEditListener
e
- the UndoableEditEvent
the
UndoableEditEvent
will be added fromaddEdit(javax.swing.undo.UndoableEdit)
public String toString()
toString
in class CompoundEdit
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