change the size of JTextField on KeyPress

Question

I have to extend the size of JTextField on KeyPressed event as user enter the text in textfield.please give me some idea how to achieve this?

thanks in advance

Answer 1

The best way I can think of is to add one CaretListener to the JTextField concerned, and with the change in the length of the Document, you Increase/Decrease the columns of the said JTextField by calling it's setColumns(...), which inturn will Increase/Decrease the size of the JTextField

Here is one example to show you, how to achieve this :

import java.awt.*;
import javax.swing.*;
import javax.swing.event.CaretEvent;
import javax.swing.event.CaretListener;

public class JTextFieldColumnExample
{
    private int columns = 1;
    private JTextField tfield;

    private void displayGUI()
    {
        JFrame frame =  new JFrame("JTextField Columns Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        final JPanel contentPane = new JPanel();
        tfield = new JTextField();
        tfield.setColumns(columns);
        tfield.addCaretListener(new CaretListener()
        {
            public void caretUpdate(CaretEvent ce)
            {
                int len = tfield.getDocument().getLength();
                if (len > columns)
                    tfield.setColumns(++columns);
                else
                {
                    if (--columns != 0)
                        tfield.setColumns(columns);
                    else
                    {
                        columns = 1;
                        tfield.setColumns(columns);
                    }   
                }   
                contentPane.revalidate();
                contentPane.repaint();
            }
        });

        contentPane.add(tfield);

        frame.setContentPane(contentPane);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    public static void main(String... args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            public void run()
            {
                new JTextFieldColumnExample().displayGUI();
            }
        });
    }
}