Bappo.net » Java swing: 'undo' e 'redo' in una JTextArea

Martedì, Agosto 18, 2009

Java swing: ‘undo’ e ‘redo’ in una JTextArea

Il seguente metodo statico prende una JTextArea e le aggiunge un UndoManager, in modo che si possano usare i tasti Ctrl-Z e Ctrl-Y per annullare e ripetere le modifiche rispettivamente (undo e redo).

/**
 * Method adds the undo/redo (Ctrl-Z/Ctrl-Y) capabilities to given JTextArea.
 * @param area JTextArea to modify.
 */
public static void addUndoRedo(JTextArea area){
	final UndoManager undoman = new UndoManager();
	// add listener
	area.getDocument().addUndoableEditListener(new UndoableEditListener(){
		public void undoableEditHappened(UndoableEditEvent evt){
			undoman.addEdit(evt.getEdit());
		}
	});
	//actions for the undo/redo commands
	AbstractAction undo_action = new AbstractAction(){
		public void actionPerformed(ActionEvent evt){
			try{
				if(undoman.canUndo()){
					undoman.undo();
				}
			} 
			catch(CannotUndoException e){ e.printStackTrace(); }
		}
	};
	
	AbstractAction redo_action = new AbstractAction(){
		public void actionPerformed(ActionEvent evt){
			try{
				if(undoman.canRedo()){
					undoman.redo();
				}
			} 
			catch(CannotRedoException e){ e.printStackTrace(); }
		}
	};
	//create and bind the undo/redo actions
	area.getActionMap().put("Undo", undo_action);
	area.getActionMap().put("Redo", redo_action);
	
	area.getInputMap().put(KeyStroke.getKeyStroke("control Z"), "Undo");
	area.getInputMap().put(KeyStroke.getKeyStroke("control Y"), "Redo");
}