Preventing Focus Lost

Question

I am trying to stop a focus lost on a JTextField. I was not able to find anything on this in the Forum or searching.
Basically, I want to prevent a user from leaving a text field when the data is invalid, so focus lost should only be granted when valid.
I tried overriding .transferFocus(), but of course you can just click on another component.
I did find something that works at times, but is very dangerous. I added a focus listener and did something like this:
            public void focusLost(FocusEvent e)
                try
                {                    Toolkit.getDefaultToolkit().getSystemEventQueue().getNextEvent();
                catch (InterruptedException ex){}
                requestFocus();
            }Calling this will remove the focus gained event after the focus lost and .requestFocus() can be called to regain focus.
Anyone have any ideas?

Answer 1

Check out the InputVerifier class.
Or, you can also use a [url http://java.sun.com/docs/books/tutorial/uiswing/components/generaltext.html#filter]Document Filter to prevent invalid character from being entered the the text field.
Or, you can use a JFormattedTextField.