JTextArea only with numbers, but allowing negative values

Question

I have a JTextArea which only has to accept numbers. This is my code:

DocumentFilter onlyNumberFilter = new AxisJTextFilter();
    final JTextArea areaTextoXMin = new JTextArea(String.valueOf(xMin));
    ((AbstractDocument)areaTextoXMin.getDocument()).setDocumentFilter(onlyNumberFilter);

Works OK for positive numbers, but not for negative numbers. How can I fix that?

EDIT: Sorry, the AxisJTextFilter was found over the Internet and I forgot about that. Its code is:

import javax.swing.text.*;
import java.util.regex.*;

public class AxisJTextFilter extends DocumentFilter
{
    public void insertString(DocumentFilter.FilterBypass fb, int offset, String text, AttributeSet attr) throws BadLocationException
    {
        StringBuilder sb = new StringBuilder();
        sb.append(fb.getDocument().getText(0, fb.getDocument().getLength()));
        sb.insert(offset, text);
        if(!containsOnlyNumbers(sb.toString())) return;
        fb.insertString(offset, text, attr);
    }
    public void replace(DocumentFilter.FilterBypass fb, int offset, int length, String text, AttributeSet attr) throws BadLocationException
    {
        StringBuilder sb = new StringBuilder();
        sb.append(fb.getDocument().getText(0, fb.getDocument().getLength()));
        sb.replace(offset, offset + length, text);
        if(!containsOnlyNumbers(sb.toString())) return;
        fb.replace(offset, length, text, attr);
    }
    public boolean containsOnlyNumbers(String text)
    {
        Pattern pattern = Pattern.compile("\\d*(\\.\\d{0,3})?");
        Matcher matcher = pattern.matcher(text);
        boolean isMatch = matcher.matches();
        return isMatch;
    }
}

never see that, check where your Document filtering negative numbers — mKorbel, Oct 03 '11 at 08:14
just a side-node: you might consider to store the pattern instead of recompiling in each call — kleopatra, Oct 03 '11 at 11:55

score 6 · Accepted Answer · answered Oct 03 '11 at 08:38

6

Try modifying the regular expression (int the validation method containsOnlyNumbers).

Pattern pattern = Pattern.compile("^[\\-\\+]?\\d+(\\.\\d+)?$");

This will accept the following numbers:

1234
-1234
+1234
1234.1234

I hope it helps

Udi

answered Oct 03 '11 at 08:38

Udi Cohen

1,259
9
12

Works correctly, but I wanted only 3 decimal digits as before, so I changed to Pattern pattern = Pattern.compile("^[\\-\\+]?\\d+(\\.\\d{0,3}+)?$"); Thanks! – Roman Rdgz Oct 03 '11 at 08:48
The string should be: "^[\\-\\+]?\\d+(\\.\\d{1,3})?$" – Udi Cohen Oct 03 '11 at 08:50
@kleopatra of course, it's strange I forgot to accept this one. Sorry! – Roman Rdgz Oct 05 '11 at 15:10

score 1 · Answer 2 · answered Oct 04 '11 at 00:03

1

This is intended as a comment on Udi's excellent post, but I can't figure out how to do that.

I think his pattern (d+) requires at least 1 digit, and it should be d? to allow 0-N digits. Because, as the user is typing, "-" is legal input. And a decimal point followed by no digits is always legal, especially while typing. It's only at the end (when you lose focus, etc., YMMV) that you can either require at least one digit, or, be accommodating and pragmatic and just treat the string "-" as 0.

And when developing these kinds of regular expressions don't forget that the user might be copying and pasting.

answered Oct 04 '11 at 00:03

user949300

15,364
7
35
66

This is a good comment. The regExp mentioned above is more suitable for the case when the text field loses focus. But it will be incorrect to change the '\d+' to '\d*' because a '-' is not a valid input. Thanks for the input! – Udi Cohen Oct 05 '11 at 13:42
Yes, _strictly_ speaking, you should have two different regExps, one for while the user is typing, and another "final test" when losing focus. Final test would not accept "-" or "", while typing must. Or you can take a looser, pragmatic approach, only use one regExp, and treat a final "-" and "" as 0. – user949300 Oct 08 '11 at 23:42

JTextArea only with numbers, but allowing negative values

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