JTable Input Verifier

Question

I am trying to create a simple Input Verifier for a JTable. I ended up with overriding the method: editingStopped(). The problem is that the event does not include informations about the cell that has been updated.

This is my "pseudo code":

  If (user finished editing a cell)  {
     Check if cell`s value is "1" or "0" or "-"  (Karnaugh-Veitch)
     If (check = false)
        setValue (cell, "");
   }

The first I tried was this here:

table.getModel().addTableModelListener(new TableModelListener() {
            @Override
            public void tableChanged(TableModelEvent e) {
                inputVerify (e.getColumn(), e.getFirstRow());
            }
});

    public void inputVerify (int column, int row) {
        boolean verified = true;
        String field = table.getValueAt(row, column).toString();

        if (field != null && field.length() == 1) {
            if ( !(field.charAt(0) == '0' || field.charAt(0) == '1' || field.charAt(0) == '-' ))
                verified = false;
        }
        else {
            verified = false;
        }

        if (!verified) {
            table.getModel().setValueAt("", row, column);
            java.awt.Toolkit.getDefaultToolkit().beep();
        }

        System.out.println ("Column = " + column + " Row = " + row + " Value = " + table.getValueAt(row, column) +" Verified = "+verified);
    }

But this ends up with an : StackOverflow Exception. I guess the problem is that: setValueAt(..) fires another tableChanged() event and an endless loop is being generated.

Now, I tried this here:

    table.getDefaultEditor(Object.class).addCellEditorListener(new CellEditorListener() {

        // called when editing stops
        public void editingStopped(ChangeEvent e) {

            // print out the value in the TableCellEditor
            System.out.println(((CellEditor) e.getSource()).getCellEditorValue().toString());

        }

        public void editingCanceled(ChangeEvent e) {
            // whatever
        }
    });

But as you can see I can just retrieve the new value of the cell, not the "coordinates". I need to call: setValueAt( .. ) method, but I dont know how to get the cell`s coordinates.

Or is there a more simple way to create an input verifier??

Best regards Ioannis K.

Answer 1

First: input validation on JTable editing is not well supported. A couple of comments

• tableChanged in a TableModelListener is not a good place to do validation, at that point in time the change already happened (the model notifies its listeners of the fact)
• as a consequence, whatever validation (verify) method hook you choose, never-ever talk back to the model, you'll end up in an infinite loop (as you have seen)
• application-provided CellEditorListeners are rather useless because a) there's no guarantee about sequence of notification (JTable might or not have already updated the model) b) the life-cylce of an editor is ill-defined

After all those (incomplete, unfortunately ;-) no-nos, a little hope: best bet is to implement a custom CellEditor which does the validation in stopCellCellEditing: if the new value isn't valid, return false and optionally provide a visual error feedback. Have a look at JTable.GenericEditor to get an idea of how that might be done