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- All Known Implementing Classes:
- AbstractDocument.DefaultDocumentEvent, AbstractDocument.ElementEdit, AbstractUndoableEdit, CompoundEdit, DefaultStyledDocument.AttributeUndoableEdit, StateEdit, UndoManager
public interface UndoableEdit
AnUndoableEdit
represents an edit. The edit may be undone, or if already undone the edit may be redone.UndoableEdit
is designed to be used with theUndoManager
. AsUndoableEdit
s are generated by anUndoableEditListener
they are typically added to theUndoManager
. When anUndoableEdit
is added to anUndoManager
the following occurs (assumingend
has not been called on theUndoManager
):- If the
UndoManager
contains edits it will calladdEdit
on the current edit passing in the new edit as the argument. IfaddEdit
returns true the new edit is assumed to have been incorporated into the current edit and the new edit will not be added to the list of current edits. Edits can useaddEdit
as a way for smaller edits to be incorporated into a larger edit and treated as a single edit. - If
addEdit
returns falsereplaceEdit
is called on the new edit with the current edit passed in as the argument. This is the inverse ofaddEdit
if the new edit returns true fromreplaceEdit
, the new edit replaces the current edit.
UndoManager
makes use ofisSignificant
to determine how many edits should be undone or redone. TheUndoManager
will undo or redo all insignificant edits (isSignificant
returns false) between the current edit and the last or next significant edit.addEdit
andreplaceEdit
can be used to treat multiple edits as a single edit, returning false fromisSignificant
allows for treating can be used to have many smaller edits undone or redone at once. Similar functionality can also be done using theaddEdit
method.
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Method Summary
Methods Modifier and Type Method and Description boolean
addEdit(UndoableEdit anEdit)
Adds anUndoableEdit
to thisUndoableEdit
.boolean
canRedo()
Returns true if this edit may be redone.boolean
canUndo()
Returns true if this edit may be undone.void
die()
Informs the edit that it should no longer be used.String
getPresentationName()
Returns a localized, human-readable description of this edit, suitable for use in a change log, for example.String
getRedoPresentationName()
Returns a localized, human-readable description of the redoable form of this edit, suitable for use as a Redo menu item, for example.String
getUndoPresentationName()
Returns a localized, human-readable description of the undoable form of this edit, suitable for use as an Undo menu item, for example.boolean
isSignificant()
Returns true if this edit is considered significant.void
redo()
Re-applies the edit.boolean
replaceEdit(UndoableEdit anEdit)
Returns true if thisUndoableEdit
should replaceanEdit
.void
undo()
Undo the edit.
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Method Detail
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undo
void undo() throws CannotUndoException
Undo the edit.- Throws:
CannotUndoException
- if this edit can not be undone
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canUndo
boolean canUndo()
Returns true if this edit may be undone.- Returns:
- true if this edit may be undone
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redo
void redo() throws CannotRedoException
Re-applies the edit.- Throws:
CannotRedoException
- if this edit can not be redone
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canRedo
boolean canRedo()
Returns true if this edit may be redone.- Returns:
- true if this edit may be redone
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die
void die()
Informs the edit that it should no longer be used. Once anUndoableEdit
has been marked as dead it can no longer be undone or redone.This is a useful hook for cleaning up state no longer needed once undoing or redoing is impossible--for example, deleting file resources used by objects that can no longer be undeleted.
UndoManager
calls this before it dequeues edits.Note that this is a one-way operation. There is no "un-die" method.
- See Also:
CompoundEdit.die()
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addEdit
boolean addEdit(UndoableEdit anEdit)
Adds anUndoableEdit
to thisUndoableEdit
. This method can be used to coalesce smaller edits into a larger compound edit. For example, text editors typically allow undo operations to apply to words or sentences. The text editor may choose to generate edits on each key event, but allow those edits to be coalesced into a more user-friendly unit, such as a word. In this case, theUndoableEdit
would overrideaddEdit
to return true when the edits may be coalesced.A return value of true indicates
anEdit
was incorporated into this edit. A return value of false indicatesanEdit
may not be incorporated into this edit.Typically the receiver is already in the queue of a
UndoManager
(or otherUndoableEditListener
), and is being given a chance to incorporateanEdit
rather than letting it be added to the queue in turn.If true is returned, from now on
anEdit
must return false fromcanUndo
andcanRedo
, and must throw the appropriate exception onundo
orredo
.- Parameters:
anEdit
- the edit to be added- Returns:
- true if
anEdit
may be incorporated into this edit
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replaceEdit
boolean replaceEdit(UndoableEdit anEdit)
Returns true if thisUndoableEdit
should replaceanEdit
. This method is used byCompoundEdit
and theUndoManager
; it is called ifanEdit
could not be added to the current edit (addEdit
returns false).This method provides a way for an edit to replace an existing edit.
This message is the opposite of addEdit--anEdit has typically already been queued in an
UndoManager
(or other UndoableEditListener), and the receiver is being given a chance to take its place.If true is returned, from now on anEdit must return false from canUndo() and canRedo(), and must throw the appropriate exception on undo() or redo().
- Parameters:
anEdit
- the edit that replaces the current edit- Returns:
- true if this edit should replace
anEdit
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isSignificant
boolean isSignificant()
Returns true if this edit is considered significant. A significant edit is typically an edit that should be presented to the user, perhaps on a menu item or tooltip. TheUndoManager
will undo, or redo, all insignificant edits to the next significant edit.- Returns:
- true if this edit is significant
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getPresentationName
String getPresentationName()
Returns a localized, human-readable description of this edit, suitable for use in a change log, for example.- Returns:
- description of this edit
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getUndoPresentationName
String getUndoPresentationName()
Returns a localized, human-readable description of the undoable form of this edit, suitable for use as an Undo menu item, for example. This is typically derived fromgetPresentationName
.- Returns:
- a description of the undoable form of this edit
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getRedoPresentationName
String getRedoPresentationName()
Returns a localized, human-readable description of the redoable form of this edit, suitable for use as a Redo menu item, for example. This is typically derived fromgetPresentationName
.- Returns:
- a description of the redoable form of this edit
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