JTextPane not triggering UndoableEditListener events

Question

I added an UndoManager to a JTextPane in my application, but I can't get it work:

UndoManager undoManager = new UndoManager();
textpane.getDocument().addUndoableEditListener(undoManager);

When I manually type into the text pane, then try to undo the changes, nothing ever happens undoManager.canUndo() always returns false.

I also tried another way of adding the manager as follows:

textpane.getDocument().addUndoableEditListener(new UndoableEditListener()
{
    @Override
    public void undoableEditHappened( UndoableEditEvent e )
    {
        System.out.println("UndoableEditEvent");
        undoMgr.addEdit(e.getEdit());
    }
});

With the above code I can see in the output window that the undoableEditHappened( UndoableEditEvent e ) is called once at the start (most likely by a read call which loads the test file). When I make changes (via keyword) or insertText(...) calls, there are no further listener calls.

I found some similar questions here in StackOverflow, but the solutions were always alongs the lines that they had custom input methods for the JTextPane , I don't ... not that I know of.

What might I have overlooked?

Answer 1

I found out why the UndoableEditListener wasn't triggering.

I was calling JTextPane.read(Reader reader, Object object) after I had setup the Document listeners - What I didn't know was that calling the read(...) method creates and adds a new Document model to the JTextPane , which basically removed anything I had previously done to the old Document .

Solution

Work with the Document model after calling JTextPane.read(...)