public interface UndoableEdit
UndoableEdit represents an edit. The edit may
be undone, or if already undone the edit may be redone.
UndoableEdit is designed to be used with the
UndoManager. As UndoableEdits are generated
by an UndoableEditListener they are typically added to
the UndoManager. When an UndoableEdit
is added to an UndoManager the following occurs (assuming
end has not been called on the UndoManager):
UndoManager contains edits it will call
addEdit on the current edit passing in the new edit
as the argument. If addEdit 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 use addEdit as a way for smaller edits to
be incorporated into a larger edit and treated as a single edit.
addEdit returns false replaceEdit
is called on the new edit with the current edit passed in as the
argument. This is the inverse of addEdit
if the new edit returns true from replaceEdit, the new
edit replaces the current edit.
UndoManager makes use of
isSignificant to determine how many edits should be
undone or redone. The UndoManager will undo or redo
all insignificant edits (isSignificant returns false)
between the current edit and the last or
next significant edit. addEdit and
replaceEdit can be used to treat multiple edits as
a single edit, returning false from isSignificant
allows for treating can be used to
have many smaller edits undone or redone at once. Similar functionality
can also be done using the addEdit method.| Modifier and Type | Method and Description |
|---|---|
boolean |
addEdit(UndoableEdit anEdit)
Adds an
UndoableEdit to this UndoableEdit. |
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 this
UndoableEdit should replace
anEdit. |
void |
undo()
Undo the edit.
|
void undo() throws CannotUndoException
CannotUndoException - if this edit can not be undoneboolean canUndo()
void redo() throws CannotRedoException
CannotRedoException - if this edit can not be redoneboolean canRedo()
void die()
UndoableEdit 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.
CompoundEdit.die()boolean addEdit(UndoableEdit anEdit)
UndoableEdit to this UndoableEdit.
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, the UndoableEdit would
override addEdit 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 indicates anEdit
may not be incorporated into this edit.
Typically the receiver is already in the queue of a
UndoManager (or other UndoableEditListener),
and is being given a chance to incorporate anEdit
rather than letting it be added to the queue in turn.
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.
anEdit - the edit to be addedanEdit may be incorporated into this
editboolean replaceEdit(UndoableEdit anEdit)
UndoableEdit should replace
anEdit. This method is used by CompoundEdit
and the UndoManager; it is called if
anEdit 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().
anEdit - the edit that replaces the current editanEditboolean isSignificant()
UndoManager will undo,
or redo, all insignificant edits to the next significant edit.String getPresentationName()
String getUndoPresentationName()
getPresentationName.String getRedoPresentationName()
getPresentationName. Submit a bug or feature
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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