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Aug 4th, 2005

For the Swing gurus

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yes, there's an area of Java I'm almost a complete novice in (so far, I'm going full steam ahead :cheesy: ).

I've the following code to filter out non-numeric input from a JTextField (which is meant to contain a timeout interval in minutes, that's why).

Java Syntax (Toggle Plain Text)
    private void dumpNonNumericInput(KeyEvent e) {
        char input = e.getKeyChar();
        String oldText = ((JTextField)e.getSource()).getText();
        if (input != KeyEvent.VK_BACK_SPACE && input != KeyEvent.VK_DELETE &&
            (input < '0' || input > '9')) {
            JOptionPane.showMessageDialog(this, "Numeric input required",
                                          "Input error",
                                          JOptionPane.ERROR_MESSAGE);
            e.consume();
            ((JTextField)e.getSource()).setText(oldText);
 
        }
    }
    private void dumpNonNumericInput(KeyEvent e) {
        char input = e.getKeyChar();
        String oldText = ((JTextField)e.getSource()).getText();
        if (input != KeyEvent.VK_BACK_SPACE && input != KeyEvent.VK_DELETE &&
            (input < '0' || input > '9')) {
            JOptionPane.showMessageDialog(this, "Numeric input required",
                                          "Input error",
                                          JOptionPane.ERROR_MESSAGE);
            e.consume();
            ((JTextField)e.getSource()).setText(oldText);

        }
    }

This method works like a charm, that's not the problem.
The problem is that is I remove the error message popup (just the showMessageDialog command) the method no longer removes the faulty input either.
I THINK it's something to do with Swing thread timing, but I'm not sure.
Neither do I know how to cure this, which is more important at the moment as I'd rather not have that popup appear every time someone makes a typo.

I could probably subclass JTextField but that may be more trouble than it's worth.

jwenting

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duckman

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Aug 5th, 2005

Re: For the Swing gurus

Can you do it with a try catch statement?

ProFreelance

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Newbie Poster

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Aug 5th, 2005

Re: For the Swing gurus

A better alternative would be to disable text input altogether (call setEditable(false) on the text field. This deals with the problem of people putting in garbage input. Then all you need to do is use regular expression on the character that was input. Then use reg exp for input
if(stringvar.matches("\\d")){}

Not sure why removing a showMessageDialog would have any effect on the following code.

Gink

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Light Poster

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Aug 5th, 2005

Re: For the Swing gurus

hi jwenting,

I have attached a Textfield which takes number of columns(maximum number of characters that the textfield can take) as parameter. If you use the usual textfields with keylistener, you can set illegal characters programattically. This textfield(one attached) does not allow illegal characters either by entry or progammatically. You can run the program attached and check out and tell me whether it was useful.

TextFieldDemo is the one with main method.

I am not sure whether this is exactly your requirement

regards
Srinivas

Attached Files

	NumericTextField.java (1.7 KB, 22 views)
	TextFieldDemo.java (280 Bytes, 14 views)

cheenu78

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Aug 5th, 2005

Re: For the Swing gurus

Cheers, I'll give it a look.

Gink, the idea is to allow only certain input. If it were readonly I'd have used a label or something else instead

jwenting

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duckman

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Aug 5th, 2005

Re: For the Swing gurus

Im not suggesting to make it read-only. What im saying is add a keylistener and whenever the user presses a key just update the textfield accordingly. The only reason I said uneditable is to prevent people from typing in characters that the keylistener doesnt respond to. It is still editable by the program, and the user wont know it's uneditable.

Gink

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Aug 5th, 2005

Re: For the Swing gurus

ah.

Found I can't catch shortcut keys (like Alt-T, Alt-X, etc.) using this system so I abandoned it.
Instead I now validate the field when it's value is read out instead of when it's input and give an error then.

jwenting

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duckman

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Aug 5th, 2005

Re: For the Swing gurus

Why not a boolean check method?

Java Syntax (Toggle Plain Text)
public boolean check(String text)
{
   try
   {
        Double.parseDouble(text);
        return true;
   }
   catch
   {
       JOptionPane.showMessageDialog(null,"Numeric crap only");
       return false;
   }
   return false;
}
public boolean check(String text)
{
   try
   {
        Double.parseDouble(text);
        return true;
   }
   catch
   {
       JOptionPane.showMessageDialog(null,"Numeric crap only");
       return false;
   }
   return false;
}

server_crash

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Postaholic

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Aug 5th, 2005

Re: For the Swing gurus

yes, something like that

Thought to be a tad more friendly with my users though :p

Java Syntax (Toggle Plain Text)
        try {
            Integer.parseInt(timeout.getText());
        } catch (NumberFormatException ex) {
            JOptionPane.showMessageDialog(this,
                                          "Timeout interval must be a number",
                                          "Input error",
                                          JOptionPane.ERROR_MESSAGE);
            return;
        }
        try {
            Integer.parseInt(timeout.getText());
        } catch (NumberFormatException ex) {
            JOptionPane.showMessageDialog(this,
                                          "Timeout interval must be a number",
                                          "Input error",
                                          JOptionPane.ERROR_MESSAGE);
            return;
        }

jwenting

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duckman

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Aug 5th, 2005

Re: For the Swing gurus

What do you mean your users? Are you teaching a class or something? Will however see the code?

server_crash

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