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Controlling text in a JTextField.

Posted on 2004-03-30
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Last Modified: 2010-03-31
I have 2 books on Java and wouldn't you knon it, neither one gives me the information I want!

How can I control what charactors that can be entered and the number of charactors that can be entered into a JTextField?

Thanks in advance.

David, a.k.a. TrainMan
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Question by:TrainMan
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11 Comments
 
LVL 92

Expert Comment

by:objects
ID: 10719792
use a custom Document.
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LVL 92

Accepted Solution

by:
objects earned 60 total points
ID: 10719800
public class FieldDocument extends PlainDocument
{
     private int limit;

     public FieldDocument(int limit)
     {
          super();
          this.limit = limit;
     }

     public void insertString(int offset, String s, AttributeSet attributeSet)
          throws BadLocationException
     {
          if (limit==0 || getLength() + s.length() < limit)
          {
  // if we haven't reached the limit, insert the string
               super.insertString(offset, s, attributeSet);
          }
          else
          {
                        // otherwise, just lose the string

               Toolkit.getDefaultToolkit().beep();
          }
     
     }
}
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LVL 92

Expert Comment

by:objects
ID: 10719809
You can use a similiar technique to limit what characters can be entered.
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Author Comment

by:TrainMan
ID: 10720235
Thanks for the input.  But while this is an answer, it isn't what I'm looking for.  
So let me clearify my question.

How can I do this for each charactor as it is entered?
I do believe that that is posible using MFC C++ in Windows.

David
0
 
LVL 92

Expert Comment

by:objects
ID: 10720270
the above will handle that, insertString() is called whenever any character(s) are inserted into the text field.
0
 
LVL 9

Expert Comment

by:mmuruganandam
ID: 10720984
http://www.iam.ubc.ca/guides/javatut99/uiswing/components/textfield.html

This might help you in validating each and every character that you enter.


Otherwise, you can add the key listener to your text fields.  So that you will get the event firing for every key you press.
0
 
LVL 9

Expert Comment

by:mmuruganandam
ID: 10721029
http://java.sun.com/developer/JDCTechTips/2001/tt1120.html

This would also help you.  There are more than one way to control your text.
0
 
LVL 30

Expert Comment

by:Mayank S
ID: 10721158
objects' code should help. Have a look at this for more example:

http://www.experts-exchange.com/Programming/Programming_Languages/Java/Q_20910569.html
0
 

Author Comment

by:TrainMan
ID: 10725112
Boy, I asked for help and I sure got it.  Thanks to evaryone.

I'll need a couple of days though to sort through all of the suggestions.

Talk to you then.

TrainMan
0
 

Author Comment

by:TrainMan
ID: 10766569
Sorry everyone.  It  was my intent to split the point to the 3 of you.

TrainMan
0
 
LVL 30

Expert Comment

by:Mayank S
ID: 10767755
You can post a question in Community Support asking them to re-open this question so that you can split between the 3, or you can post points for mmuruganandam and mayankeagle in separate questions, giving links to this one and ask them to post comments on those, so that you can accept them and give the points.
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