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javax.swing.undo
public interface: UndoableEdit [javadoc | source]

All Known Implementing Classes:
    InsertUndo, UndoableRemoveEntry, RemoveUndo, UndoManager, UndoableFieldChange, RemoveUndo, UndoableMoveString, UndoableStringChange, DefaultDocumentEvent, InsertUndo, CountingUndoManager, AttributeUndoableEdit, CompoundEdit, UndoableInsertEntry, StateEdit, UndoableAddOrRemoveGroup, UndoableInsertString, AbstractUndoableEdit, UndoableRemoveString, ElementEdit, UndoableModifyGroup, UndoablePreambleChange, NamedCompound, StyleChangeUndoableEdit

An 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):

  1. If the 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.
  2. If 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.
The 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.
Method from javax.swing.undo.UndoableEdit Summary:
addEdit,   canRedo,   canUndo,   die,   getPresentationName,   getRedoPresentationName,   getUndoPresentationName,   isSignificant,   redo,   replaceEdit,   undo
Method from javax.swing.undo.UndoableEdit Detail:
 public boolean addEdit(UndoableEdit anEdit)
    Adds an 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.
 public boolean canRedo()
    Returns true if this edit may be redone.
 public boolean canUndo()
    Returns true if this edit may be undone.
 public  void die()
    Informs the edit that it should no longer be used. Once an
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.
 public String getPresentationName()
    Returns a localized, human-readable description of this edit, suitable
for use in a change log, for example.
 public 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 from getPresentationName.
 public 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 from getPresentationName.
 public 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. The UndoManager will undo,
or redo, all insignificant edits to the next significant edit.
 public  void redo() throws CannotRedoException
    Re-applies the edit.
 public boolean replaceEdit(UndoableEdit anEdit)
    Returns true if this 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().
 public  void undo() throws CannotUndoException
    Undo the edit.