I have tried to use the example shown here but java showing error message of
"AttributeSet cannot be resolved to a type"
That is why I am trying to use another method of allowing only digits:
txtUsername.addKeyListener(new MyKeyListener());
public class MyKeyListener extends KeyAdapter{
public void keyPressed(KeyEvent ke){
System.out.println("Key pressed code = "+ke.getKeyCode());
if (ke.getKeyCode()>=48 && ke.getKeyCode()<=57)
return true;
else
return false;
}
}
But of course it is not working because keyPressed
method is void
. So, what to do in order to print only digits in textfield?
Here check this code snippet, that's how you allow only digits in JTextField, by using DocumentFilter, as the most effeciive way :
import java.awt.*;
import javax.swing.*;
import javax.swing.text.AbstractDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.DocumentFilter;
import javax.swing.text.DocumentFilter.FilterBypass;
public class InputInteger
{
private JTextField tField;
private MyDocumentFilter documentFilter;
private void displayGUI()
{
JFrame frame = new JFrame("Input Integer Example");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
JPanel contentPane = new JPanel();
contentPane.setBorder(
BorderFactory.createEmptyBorder(5, 5, 5, 5));
tField = new JTextField(10);
((AbstractDocument)tField.getDocument()).setDocumentFilter(
new MyDocumentFilter());
contentPane.add(tField);
frame.setContentPane(contentPane);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args)
{
Runnable runnable = new Runnable()
{
@Override
public void run()
{
new InputInteger().displayGUI();
}
};
EventQueue.invokeLater(runnable);
}
}
class MyDocumentFilter extends DocumentFilter
{
@Override
public void insertString(DocumentFilter.FilterBypass fp
, int offset, String string, AttributeSet aset)
throws BadLocationException
{
int len = string.length();
boolean isValidInteger = true;
for (int i = 0; i < len; i++)
{
if (!Character.isDigit(string.charAt(i)))
{
isValidInteger = false;
break;
}
}
if (isValidInteger)
super.insertString(fp, offset, string, aset);
else
Toolkit.getDefaultToolkit().beep();
}
@Override
public void replace(DocumentFilter.FilterBypass fp, int offset
, int length, String string, AttributeSet aset)
throws BadLocationException
{
int len = string.length();
boolean isValidInteger = true;
for (int i = 0; i < len; i++)
{
if (!Character.isDigit(string.charAt(i)))
{
isValidInteger = false;
break;
}
}
if (isValidInteger)
super.replace(fp, offset, length, string, aset);
else
Toolkit.getDefaultToolkit().beep();
}
}
@Override
public void insertString(FilterBypass fb, int off
, String str, AttributeSet attr)
throws BadLocationException
{
// remove non-digits
fb.insertString(off, str.replaceAll("\\D++", ""), attr);
}
@Override
public void replace(FilterBypass fb, int off
, int len, String str, AttributeSet attr)
throws BadLocationException
{
// remove non-digits
fb.replace(off, len, str.replaceAll("\\D++", ""), attr);
}