JTextField Difficulty

Hi,

        He is the code I am using to enter only numbers

 
    Put a filtering document in you JTextField is best.
  Here is the class that I use to filter out thing basis on the  
  mask string.
 
  In you application, You only need to do:
 
 
      JTextField jtf = new JTextField(();
      //
      // Only allow numeric 0,1,2,3,4,5,6,7,8,9 to be entered
      //
      jtf.setDocument(new MyTextFilter(MyTextFilter.NUMERIC));
 
  Let me know if you need further help.  Have fun!
 
//
// file MyTextFilter.java
//
import com.sun.java.swing.text.AttributeSet;
import com.sun.java.swing.text.BadLocationException;
import com.sun.java.swing.text.PlainDocument;
 
public class MyTextFilter
  extends PlainDocument
{
  public static final String LALPHA        =
"abcdefghijklmnopqrstuvwxyz";
  public static final String UALPHA        =
"ABCDEFGHIJKLMNOPQRSTUVWXYZ";
  public static final String ALPHA         = LALPHA + UALPHA;
  public static final String NUMERIC       = "0123456789";
  public static final String ALPHA_NUMERIC = ALPHA + NUMERIC;
  public MyTextFilter()
  {
    this(ALPHA_NUMERIC);
  }
  public MyTextFilter(String p_charset)
  {
    m_charset = p_charset;
  }
  public void insertString(int          p_offset,
                           String       p_str,
                           AttributeSet p_attr)
    throws BadLocationException
  {
    if (p_str == null)
      return;
 
    for (int i=0; i<p_str.length(); i++)
      if (m_charset.indexOf(p_str.valueOf(p_str.charAt(i))) == -1)
        return;
     
    super.insertString(p_offset, p_str, p_attr);
  }
 
  /**
   * the allow input character set
   */
  protected String m_charset = null;
}

:-)

bye

Mohan

Hi again,


       Here is the code to limit the no. of characters.
---------------------------------

import com.sun.java.swing.text.*;

public class LimitedPlainDocument extends DFPlainDocument
{
        public LimitedPlainDocument (int maxLength)
        {
                this.maxLength = maxLength;
        }

        private int maxLength;
       
        public final int getMaxLength()
                {
                        return maxLength;
                }
       
        public final void setMaxLength (int maxLength)
                {
                        this.maxLength = maxLength;
                }
       
        public void insertString (int offs, String str, AttributeSet a)
throws
BadLocationException
        {
                if (str == null || getLength() + str.length() <= maxLength)
                            super.insertString (offs, str, a);
                else
                {
                        int remainder = maxLength - getLength();
                        if (remainder > 0)
                                super.insertString (offs, str.substring (0,
remainder), a);
                }
        }
}

call jTextField.setDocument(new LimitedPlainDocument(5));

and u won't be able to enter more than 5 chars even using Clipboard operations.

:-)

bye

Mohan

here's my simplified solution:

class DocumentListenerExample extends JPanel implements DocumentListener, KeyListener {

  JTextField Field = null;

  public class DocumentListenerExample() {
    Field = new JTextField();
    getContainer().add(Field);
    Field.getDocument().addDocuementListener(this);
    Field.addKeyListener(this);
  }

  public void changeUpdate(DocumentEvent evt) { }

  public void insertUpdate(DocumentEvent evt) {
    removeUpdate(evt);
  }

  public void removeUpdate(DocumentEvent evt) {
    String error = validate(Field.getText());
    if (error != null) {
      //System.out.println("Error: " + error);
      // show dialog or something...
    }
  }

  protected String validate(String text) {
    int num = -1;
    try {
      num = Integer.parseInt(text);
    }
    catch (NumberFormatException e) {
      return e.getText();
    }

    if (num < 0) return "Number cannot be negative.";

    return null;
  }

  public void keyPressed(KeyEvent e) {}
  public void keyReleased(KeyEvent e) {}

  public void keyTyped(KeyEvent e) {
    if ((int) e.getKeyChar() == KeyEvent.VK_ENTER) {
      //DO SOMETHING...
    }
  }

  public static final void main(String args[]) {
    JFrame f = new JFrame();
    f.getContainer().add(new DocumentListenerExample());
    f.pack();
    f.show()
  }
}


I didnt compile this program but should do the trick...

Hope it helps,
Rob

Hi Mohan & Rob

Thanks for the solutions. The difference between the two solutions are many. As I had specified. I wanted to restrict the user to input only 4 characters ( which Mohan gave me a solution ). The second was to input only numeric
values to the same textfield. this though Mohan has given me the solution. I am not sure how to combine the 1st and the second requirement together because u can setDocument to one class at a time. Also Mohan once u set the textfield to be numeric, u need not write the code for -ve numbers or do we ?.

Rob your solution allows me to enter non-numeric which is validated later. This is not what I wanted.

Mohan can u tell me how to combine the NUMERIC and the MAXLENGTH together in one Document class

Appreciate it.

Bijoy

Mohan,

I could combine the two functionalities within the same class and thanks a lot for your help.

Bijoy.