UI Field showing only integers

Question

Hi all
I need to create a field on a form that only allows the user to input whole numbers (integers).
I've implemented this as follows:
private JFormattedTextField readTimeOut;
protected void createComponents()
        NumberFormatter numberFormatter = new IntegerFormatter();
        readTimeOut = new JFormattedTextField(numberFormatter);
        readTimeOut.setHorizontalAlignment(SwingConstants.RIGHT);
}This works in the sense that it only allows integer values in the field, and along with other code, does just about everything I need.
The only problem I have is changing the number entirely. The numberFormatter will not let me delete the last character in the field.
E.g.
If the initial value is 600,000, and I delete the 6, the field shows 0. I cannot delete this zero so that the field is empty, which I need to do.
If I delete the zeros one after the other, I am left with a 6 that I can't delete.
This is not good, because to update the field from 600,000 to 12 (for example), I have to do the following:
1. Delete all the zeros, leaving the 6.
2. Enter 12, meaning the value in the field is now 612, or 126 depending on how the initial value was modified by the user.
3. Delete the 6.
I've looked at the NumberFormatter and IntegerFormatter classes and documentation but can't see anything that allows the field to contain blank values.
Is there an option to allow an IntegerFormatter to have a blank field?
If not, can anyone suggest another way of doing this?
Thanks

Answer 1

Kleopatra wrote:
what is IntegerFormatter, custom class? Or did you mean:
NumberFormatter numberFormatter = new NumberFormatter(NumberFormat.getIntegerInstance());    Anyway, what happens is that
- NumberFormat doesn't accept null, throws a parse exception
- JFormattedTextField doesn't accept values if the format objects
That leaves 2 locations to tackle
a) implement a custom format which does handle the null (as does SwingX NumberFormatExt)
b) subclass JFormattedTextField and manually null the value in commitEdit if the text is empty
CU
Jeanette
BTW: the Swing folks hang out in .. the Swing forum :-)
BTW2: folks here seem to like wild guessing games <g>
Edited by: Kleopatra on Apr 6, 2011 2:50 PMThanks for all the replies. I've got it working with a DocumentListener, but that loses the thousands formatting. Not a disaster, but something to consider.
Jeanette, you're right, the IntegerFormatter is a custom class that extends NumberFormatter. I didn't realise this. I'm still fairly new to Java, and am still learning using existing code in the product I'm developing.
Of the two options above, I think I prefer using a custom format. I'd assumed the IntegerFormatter class was a standard class, so hadn't thought of changing it. As that's already custom I can either change that or create my own version.
Thanks for the help.
Alex
BTW: The Swing forum is well hidden. I've only now found it because you pointed out that it existed. ;-)