How will the typed character in a textField not be printed

Question

Hi all, I want to trap the typed characterfrom the user in a txtField. If
the character is not digit it will not be printed in the componet. I used
keytyped event with the folloing code...
      char typedChar = e.getKeyChar();
      String currText =txtFldMsBdIndxWeight.getText();
      if (!Character.isDigit(typedChar))
         if (currText.length()!=0)
            currText = currText.substring(0, currText.length()-1);
            txtFldMsBdIndxWeight.setText(currText);
        else  txtFldMsBdIndxWeight.setText("");
      the problem is when the text of the componet is empty (currText.length()==0)
the non digit character will be printed in the componet, the code...
txtFldMsBdIndxWeight.setText("");is not working.
What am i doing wrong thank you for advance,
Kostas

Answer 1

Here is the JNumberField implementation for you
Ashish
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.text.*;
* <P>This Class is used to create number Text Field
public class JNumberField extends JTextField {
private boolean isReal=false;
private int digitCount;
private boolean copyPasteSupported=true;
* <P>This is a default constructor.It creates text field with length of 10 , right aligned and
* without decimal point
* @param
* @return
public JNumberField()
this(10,RIGHT,false);
* <P>This constructor creates text field with specified length , right aligned and
* without decimal point
* @param integer digitCount indicates the length of the text field
* @return
public JNumberField(int digitCount)
this(digitCount,RIGHT,false);
* <P>This constructor creates text field with specified length,specified aligned and
* without decimal point
* @param int digitCount indicates the length of the text field
* int alignment indicates the alignment.It can be LEFT or RIGHT
* @return
public JNumberField(int digitCount,int alignment)
this(digitCount,alignment,false);
* <P>This constructor creates text field with specified length,specified aligned and
* flag to assign decimal point
* @param int digitCount indicates the length of the text field
* int alignment indicates the alignment.It can be LEFT orRIGHT
* boolean isReal flag to set decimal point
* @return
public JNumberField(int digitCount,int alignment,boolean isReal)
this(digitCount,alignment,isReal,false);
* <P>This constructor creates text field with specified length,specified aligned and
* flags to assign decimal point and to support copy paste operation
* @param int digitCount indicates the length of the text field
* int alignment indicates the alignment.It can be LEFT or RIGHT
* boolean isReal flag to set decimal point
* boolean copyPasteSupported flag to support copy paste
* @return
public JNumberField(int digitCount,int alignment,boolean isReal,boolean copyPasteSupported)
setDocument(new NumberDocument());
setDigitCount(digitCount);
setHorizontalAlignment(alignment);
setReal(isReal);
setCopyPasteSupported(copyPasteSupported);
addKeyListener(new JNumberFieldKeyAdapter());
* <P>This method sets the flag to support copy paste operation
* @param boolean copyPasteSupported flag to support copy paste
* @return
public void setCopyPasteSupported(boolean copyPasteSupported)
this.copyPasteSupported=copyPasteSupported;
* <P>This method checks the copy paste is supported
* @param
* @ return boolean copyPasteSupported flag
public boolean isCopyPasteSupported()
return copyPasteSupported;
* <P>This method sets the Real Value support flag
* @ param boolean isReal flag to set the Real value
* @ return
public void setReal(boolean isReal)
this.isReal=isReal;
* <P>This method checks whether Real Value is accepted
* @param
* @ return boolean isReal flag
public boolean isReal()
return isReal;
* <P>This method sets the text alignment
* @param int alignment value can be LEFT or RIGHT
* @return
public void setHorizontalAlignment(int alignment)
if(alignment==LEFT || alignment==RIGHT)
super.setHorizontalAlignment(alignment);
* <P>This method gets the no of digits of text field
* @param
* @return int digitCount
public int getDigitCount()
return digitCount;
* <P>This method sets the no of digits of text field
* @param int digitCount of text field
* @return
public void setDigitCount(int digitCount)
this.digitCount=digitCount;
* <P>This is an inner Class which overrides the Document Class
public class NumberDocument extends PlainDocument {
* <P>This method overrides insertString method of PlainDocument Class
* @param int offset - The Location of a String to be inserted
* String String str - The String to be inserted
* AttributeSet a - Attributes of a text Field
* @return
* @Exception throws BadLocationException when the offset value is negative or exceeds the
* length of the text field
public void insertString(int offset, String str, AttributeSet a) throws BadLocationException
if((getLength()+1) >getDigitCount())
return;
if(str.length()==1)
if(Character.isDigit(str.charAt(0)))
super.insertString(offset,str,a);
else
if(str.charAt(0)=='.' && isReal())
if(JNumberField.this.getText().indexOf('.')<0)
super.insertString(offset,str,a);
else
boolean isStringContainsChar=false;
for(int i=0;i<str.length();i++)
if(!Character.isDigit(str.charAt(i)))
isStringContainsChar=true;
break;
if(!isStringContainsChar)
super.insertString(offset,str,a);
* <P>This is an inner Class which listens the Key Events
public class JNumberFieldKeyAdapter extends KeyAdapter {
String textBeforKeyPressed="";
* <P>This method captures the Key Event and prevents the copy paste operation
* if copy paste is not supported
* @param KeyEvent ke - captured Key Event
* @return
public void keyPressed(KeyEvent ke)
char keyChar=ke.getKeyChar();
if(keyChar=='\r' || keyChar=='\n')
System.out.println("EnterPressed ");
String modifire=ke.getKeyModifiersText(ke.getModifiers());
if((modifire.equalsIgnoreCase("Ctrl") || keyChar=='v' || keyChar=='V')&& !isCopyPasteSupported())
ke.consume();