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Undoable edit events occur when an operation that can be undone occurs on a component. Currently, only text components fire undoable edit events, and then only indirectly. The text component's document fires the events. For text components, undoable operations include inserting characters, deleting characters, and modifying the style of text. Programs typically listen to undoable edit events to assist in the implementation of undo and redo commands.
Here is the undoable edit event handling code from an application called TextComponentDemo
.
... //where initialization occurs document.addUndoableEditListener(new MyUndoableEditListener()); ... protected class MyUndoableEditListener implements UndoableEditListener { public void undoableEditHappened(UndoableEditEvent e) { //Remember the edit and update the menus undo.addEdit(e.getEdit()); undoAction.updateUndoState(); redoAction.updateRedoState(); } }
You can find a link to the source file for TextComponentDemo
in the
example index for Using Swing Components. For a discussion about the undoable edit listener aspect of the program see
Implementing Undo and Redo
The UndoableEditListener Interface
Because UndoableEditListener
has only one method, it has no corresponding adapter class.
Method | Purpose |
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undoableEditHappened(UndoableEditEvent) | Called when an undoable event occurs on the listened-to component. |
Method | Purpose |
---|---|
(in java.util.EventObject ) |
Return the object that fired the event. |
|
Returns an
UndoableEdit |
The following table lists the examples that use undoable edit listeners.
Example | Where Described | Notes |
---|---|---|
TextComponentDemo |
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Implements undo and redo on a text pane with help from an undoable edit listener. |