Java

undo - redo function in a text editor

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undo - redo function in a text editor

Dec 22nd, 2004

I have a text editor I've been working on, and I'm having some trouble with the undo/redo functions... It doesn't work, and I don't know what's wrong with it. I posted all of my code dealing with the undo function. I know it's a lot, but maybe you wont mind helping me. Any suggestions will help.

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UndoManager undoManager;

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textArea2.getDocument().addUndoableEditListener(this);
	textArea2.addFocusListener(this);
textArea2.getDocument().addUndoableEditListener(this);
	textArea2.addFocusListener(this);

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 Java Syntax (Toggle Plain Text) 
 public void createUndoManager()
 {
	 undoManager = new UndoManager();
 }
 
 public void removeUndoManager()
 {
	 undoManager.end();
 }
  public void focusGained(FocusEvent fe)
 {
	 createUndoManager();
 }
 public void focusLost(FocusEvent fe)
 {
	 removeUndoManager();
 }
 public void undoableEditHappened(UndoableEditEvent uee) 
 {
	 undoManager.addEdit(uee.getEdit());
 }
 public void createUndoManager()
 {
	 undoManager = new UndoManager();
 }

 public void removeUndoManager()
 {
	 undoManager.end();
 }
  public void focusGained(FocusEvent fe)
 {
	 createUndoManager();
 }
 public void focusLost(FocusEvent fe)
 {
	 removeUndoManager();
 }
 public void undoableEditHappened(UndoableEditEvent uee) 
 {
	 undoManager.addEdit(uee.getEdit());
 }

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 Java Syntax (Toggle Plain Text) 
public void undoableEditHappened(UndoableEditEvent uee) 
 {
	 undoManager.addEdit(uee.getEdit());
 }
public void undoableEditHappened(UndoableEditEvent uee) 
 {
	 undoManager.addEdit(uee.getEdit());
 }

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 Java Syntax (Toggle Plain Text) 
if ((ae.getSource() == btnUndo) || ae.getActionCommand().equals("Undo"))
{	
 try
	 {
		 undoManager.undo();
	 }
	 catch (CannotUndoException cue)
	 {
		 Toolkit.getDefaultToolkit().beep();
	 }
 }
}
if ((ae.getSource() == btnUndo) || ae.getActionCommand().equals("Undo"))
{	
 try
	 {
		 undoManager.undo();
	 }
	 catch (CannotUndoException cue)
	 {
		 Toolkit.getDefaultToolkit().beep();
	 }
 }
}

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Join Date: Jun 2004

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Re: undo - redo function in a text editor

Jan 3rd, 2005

Hi everyone,

You are resetting your UndoManager class every time so there is always nothing to undo. Basically remove the createUndoManager() function and create that class once as a global class with a global instance only once.

Don't forget the import stsement for the undo class as well

Richard West