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JTextField Text Validation

Posted on 2001-06-16
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Last Modified: 2007-11-27
I am trying to catch the users input for binary validation.

Example:

1) The user will attempt to edit an existing binary string in a JTextField "00001111"
2) If the user enters any text  other than a '1' or a '0',  I want there input to be rejected and the original string remain in the TextField
3) If the user inputs a '1' or a '0'..it will replace the bit as requested

I have a Document listener on thh Field, limiting the amount of binary bits in my string.

I need help on Java Text Validation??

Thanks
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Question by:Vernstump
  • 2
3 Comments
 
LVL 92

Accepted Solution

by:
objects earned 100 total points
Comment Utility
You need to define your own Document model. For your needs it sounds like you simply need to extend PlainDocument, overriding insertString() something like this:

class BinaryDocumentModel extends PlainDocument
{
  public void insertString(int off, String s, AttributeSet a) throws BadLocationException
{
  if (s is only contains 0's & 1's)
    super.insertString(off, s, a);
  else
    Toolkit.getDefaultToolkit.beep();
}
0
 
LVL 7

Expert Comment

by:Sasha_Mapa
Comment Utility
Check out these 2 classes:

package free.util;

import javax.swing.text.PlainDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.AbstractDocument;
import java.awt.Toolkit;


/**
 * A PlainDocument extension which allows to disallow certain changes,
 * by implementing the isChangeAccepted(String, String) method and returning
 * false. A beep is emitted when an attempt to make an unacceptable change is
 * made.
 */

public abstract class StrictPlainDocument extends PlainDocument{



  public StrictPlainDocument(){
    super();
  }



  protected StrictPlainDocument(AbstractDocument.Content c){
    super(c);
  }



  /**
   * Overrides PlainDocument.insertString(int, String, AttributeSet) to
   * check whether the change is accepted before applying the change.
   */

  public void insertString(int offs, String str, AttributeSet a) throws BadLocationException{
    String oldString = getText(0,getLength());
    String newString = new StringBuffer(oldString).insert(offs,str).toString();

    if (isChangeAccepted(oldString,newString))
      super.insertString(offs,str,a);
    else
      Toolkit.getDefaultToolkit().beep();
  }



  /**
   * Returns true if the change from the old text to the new text is acceptable,
   * returns false otherwise.
   */

  public abstract boolean isChangeAccepted(String oldText, String newText);


}





package free.util;


/**
 * A StrictPlainModel which only allows inputting an integer value in a certain
 * range.
 */

public class IntegerStrictPlainDocument extends StrictPlainDocument{

 
  /**
   * The minimum allowed value.
   */

  private final long minValue;



  /**
   * The maximum allowed value.
   */

  private final long maxValue;



  /**
   * The radix of the input.
   */

  private final int radix;




  /**
   * Creates a new IntegerStrictPlainDocument which will only allow inputting
   * integer values in the given radix in the range [minValue..maxValue].
   *
   * @param minValue The minimum allowed value.
   * @param maxValue The maximum allowed value.
   * @param radix The radix of the input.
   */

  public IntegerStrictPlainDocument(long minValue, long maxValue, int radix){
    this.minValue = minValue;
    this.maxValue = maxValue;
    this.radix = radix;
  }




  /**
   * Creates a new IntegerStrictPlainDocument which will only allow inputting
   * integer values in the range [minValue..maxValue].
   *
   * @param minValue The minimum allowed value.
   * @param maxValue The maximum allowed value.
   */

  public IntegerStrictPlainDocument(long minValue, long maxValue){
    this(minValue, maxValue, 10);
  }




  /**
   * Returns true if the new text represents an integer in the correct range when
   * parsed using the appropriate radix, returns false otherwise.
   */

  public boolean isChangeAccepted(String oldText, String newText){
    try{
      long val = Long.parseLong(newText,getRadix());
      if ((val<getMinValue())||(val>getMaxValue()))
        return false;
      else
        return true;
    } catch (NumberFormatException e){
        return false;
      }
  }




  /**
   * Returns the radix used by this IntegerStrictPlainDocument to parse the text.
   */
 
  public int getRadix(){
    return radix;
  }




  /**
   * Returns the minimal allowed value.
   */

  public long getMinValue(){
    return minValue;
  }



  /**
   * Returns the maximal allowed value.
   */

  public long getMaxValue(){
    return maxValue;
  }

 

}


You can use IntegerStrictPlainDocument with new IntegerStrictPlainDocument(Long.MIN_VALUE,Long.MAX_VALUE,2) for what you want.


Sasha Maryanovsky.
0
 
LVL 92

Expert Comment

by:objects
Comment Utility
Thanks for the points :)
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