JTextField - Setting the column size doesn't work. Help, please.

Question

Hi,
I want to set the column size of a text field from another text field by the input from the user. However, it just doesn't work. The following is my code. Just check out the last anonymous inner class action listener. Somehow i can get the user text, but it just doesn't work.
Thanks for any helpful inputs.
* Introduction to Java Programming: Comprehensive, 6th Ed.
* Excercise 15.11 - Demonstrating JTextField properties, dynamically.
* @Kaka Kaka
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.Border;
import javax.swing.border.LineBorder;
import javax.swing.border.TitledBorder;
public class Ex15_11 extends JFrame{
    // Create two text fields and three radio buttons
    private JTextField jtfUserText = new JTextField(10);
    private JTextField jtfColumnSize = new JTextField(new Integer(10));
    private JRadioButton jrbLeft = new JRadioButton("Left");
    private JRadioButton jrbCenter = new JRadioButton("Center");
    private JRadioButton jrbRight = new JRadioButton("Right");
    public static void main(String[] args){
        Ex15_11 frame = new Ex15_11();
        frame.pack();
        frame.setTitle("Excercise 15.11 - Text Field Property");
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    // Start of Constructor
    public Ex15_11(){
        // Set the the frame layout
        setLayout(new BorderLayout(5, 5));
        // Create three panels and two labels
        JPanel jpText = new JPanel();
        JPanel jpHorizontalAlignment = new JPanel();
        JPanel jpColumn = new JPanel();
        JLabel jlblTextField = new JLabel("Text Field");
        JLabel jlblColumn = new JLabel("Column Size");
        // Create a button group for the radio buttons to be grouped
        ButtonGroup group = new ButtonGroup();
        // Group the radio buttons
        group.add(jrbLeft);
        group.add(jrbCenter);
        group.add(jrbRight);
        // set a titled border for a panel
        jpHorizontalAlignment.setBorder(new TitledBorder("Horizontal Alignment"));
        // Create a line border
        Border lineBorder = new LineBorder(Color.BLACK, 1);
        // the all the components to their corresponding panels
        jpText.add(jlblTextField);
        jpText.add(jtfUserText);
        jpHorizontalAlignment.add(jrbLeft);
        jpHorizontalAlignment.add(jrbCenter);
        jpHorizontalAlignment.add(jrbRight);
        jpColumn.setBorder(lineBorder);
        jpColumn.add(jlblColumn);
        jpColumn.add(jtfColumnSize);
        // add the panels to the frame
        add(jpText, BorderLayout.NORTH);
        add(jpHorizontalAlignment, BorderLayout.WEST);
        add(jpColumn, BorderLayout.EAST);
        jrbLeft.addActionListener(new ActionListener(){
            // Handle event
            public void actionPerformed(ActionEvent e) {
                jtfUserText.setHorizontalAlignment(SwingConstants.LEFT);
        jrbCenter.addActionListener(new ActionListener(){
            // Handle event
            public void actionPerformed(ActionEvent e) {
                jtfUserText.setHorizontalAlignment(SwingConstants.CENTER);
        jrbRight.addActionListener(new ActionListener(){
            // Handle event
            public void actionPerformed(ActionEvent e) {
                jtfUserText.setHorizontalAlignment(SwingConstants.RIGHT);
        // Register the listener for the coloum size
        jtfColumnSize.addActionListener(new ActionListener(){
            // Handle event
            public void actionPerformed(ActionEvent e) {
                System.out.println(Integer.parseInt(jtfColumnSize.getText()));
                jtfUserText.setColumns(Integer.parseInt(jtfColumnSize.getText()));
}Edited by: ChangBroot on Dec 16, 2008 6:13 PM

Answer 1

don't forget to revalidate the JPanel after changing the components it holds:
    jtfColumnSize.addActionListener(new ActionListener()
      // Handle event
      public void actionPerformed(ActionEvent e)
        System.out.println(Integer.parseInt(jtfColumnSize.getText()));
        jtfUserText.setColumns(Integer.parseInt(jtfColumnSize.getText()));
        jpText.revalidate();
    });This will tell the jpText JPanel's layout manager to relayout the components that this JPanel holds. It should resize your JTextField. Note that in order to call this from within the anonymous inner ActionListener jpText will need to be declared "final". Either that or declared as a class field.