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
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
UndoManagercontains edits it will call
addEditon the current edit passing in the new edit as the argument. If
addEditreturns 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
addEditas a way for smaller edits to be incorporated into a larger edit and treated as a single edit.
replaceEditis 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.
UndoManagermakes use of
isSignificantto determine how many edits should be undone or redone. The
UndoManagerwill undo or redo all insignificant edits (
isSignificantreturns false) between the current edit and the last or next significant edit.
replaceEditcan be used to treat multiple edits as a single edit, returning false from
isSignificantallows for treating can be used to have many smaller edits undone or redone at once. Similar functionality can also be done using the
void undo() throws CannotUndoException
Undo the edit.
CannotUndoException- if this edit can not be undone
Returns true if this edit may be undone.
void redo() throws CannotRedoException
Re-applies the edit.
CannotRedoException- if this edit can not be redone
Returns true if this edit may be redone.
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.
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
canRedo, and must throw the appropriate exception on
anEdit- the edit to be added
anEditmay be incorporated into this edit
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().
anEdit- the edit that replaces the current edit
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.
Returns a localized, human-readable description of this edit, suitable for use in a change log, for example.
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
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
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