javax.swing.undo
Class StateEdit
- Serializable, UndoableEdit
A helper class, making it easy to support undo and redo.
The following example shows how to use this class.
Foo foo; // class Foo implements StateEditable
StateEdit edit;
edit = new StateEdit(foo, "Name Change");
foo.setName("Jane Doe");
edit.end();
undoManager.addEdit(edit);
If
Foo’s implementation of
StateEditable considers the name as part of the editable state,
the user can now choose “Undo Name Change” or
“Redo Name Change” from the respective menu. No
further undo support is needed from the application.
The following explains what happens in the example.
- When a
StateEdit is created, the associated
StateEditable gets asked to store its state into a hash
table, StateEdit. - The application will now perform some changes to the edited
object. This typically happens by invoking methods on the edited
object.
- The editing phase is terminated by invoking the
end()
method of the StateEdit. The end() method
does two things.
- The edited object receives a second request for storing
its state. This time, it will use a different hash table,
StateEdit. - To increase efficiency, the
StateEdit now removes
any entries from StateEdit and StateEdit that have
the same key, and whose values are equal. Equality is determined
by invoking the equals method inherited from
Object. - When the user later chooses to undo the
StateEdit,
the edited object is asked to restore its state from the StateEdit table. Similarly,
when the user chooses to redo the StateEdit,
the edited object gets asked to restore its state from the StateEdit.
protected Hashtable | Object>postState- The state of
object at the time when end()
was called.
|
protected Hashtable | Object>preState- The state of
object at the time of constructing
this StateEdit.
|
protected static String | RCSID- The ID of the Java source file in Sun’s Revision Control
System (RCS).
|
protected StateEditable | object- The object which is being edited by this
StateEdit.
|
protected String | undoRedoName- A human-readable name for this edit action.
|
void | end()- Informs this
StateEdit that all edits are finished.
|
String | getPresentationName()- Returns a human-readable, localized name that describes this
editing action and can be displayed to the user.
|
protected void | init(StateEditable obj, String name)- Initializes this
StateEdit.
|
void | redo()- Redoes this edit operation.
|
protected void | removeRedundantState()- Removes all redundant entries from the pre- and post-edit state
hash tables.
|
void | undo()- Undoes this edit operation.
|
addEdit, canRedo, canUndo, die, getPresentationName, getRedoPresentationName, getUndoPresentationName, isSignificant, redo, replaceEdit, toString, undo |
clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait |
Object>postState
protected HashtableObject>postState
The state of
object at the time when
end()
was called.
Object>preState
protected HashtableObject>preState
The state of object at the time of constructing
this StateEdit.
RCSID
protected static final String RCSID
The ID of the Java source file in Sun’s Revision Control
System (RCS). This certainly should not be part of the API
specification. But in order to be API-compatible with
Sun’s reference implementation, GNU Classpath also has to
provide this field and match its value. The value used here has
been in every JDK release at least from 1.2 to 1.5.
- "$Id: StateEdit.java,v 1.6 1997/10/01 20:05:51 sandipc Exp $"
StateEdit
public StateEdit(StateEditable obj)
Constructs a StateEdit, specifying the object whose
state is being edited.
obj - the object whose state is being edited by this
StateEdit.
StateEdit
public StateEdit(StateEditable obj,
String name) Constructs a StateEdit, specifying the object whose
state is being edited.
obj - the object whose state is being edited by this
StateEdit.name - the human-readable name of the editing action.
end
public void end()
Informs this StateEdit that all edits are finished.
The edited object will be asked to store its state into StateEdit, and any redundant entries will get removed from
StateEdit and StateEdit.
init
protected void init(StateEditable obj,
String name) Initializes this StateEdit. The edited object will
be asked to store its current state into StateEdit.
obj - the object being edited.name - the human-readable name of the editing action.
removeRedundantState
protected void removeRedundantState()
Removes all redundant entries from the pre- and post-edit state
hash tables. An entry is considered redundant if it is present
both before and after the edit, and if the two values are equal.
StateEdit.java -- UndoableEdit for StateEditable implementations.
Copyright (C) 2002, 2003 Free Software Foundation, Inc.
This file is part of GNU Classpath.
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