GridBag Problem (Replacing Component)

[Jerry Crothers]

I have a class (JPanel) thats uses the gridbag layout - its a form.

One of the event handlers needs to remove a textfield and replace it with a another component (JButton). So I am writing code like this to remove the textfield:

this.remove(textfield);
this.repaint();
this.setVisible(true);

thats fine, but it won't let me create a new JButton (or any component) and put it in that cell. So then I tried to put the original textfield back:

add(textfield, gridbagconstraints);

..and it was there. Even just add(textfield) put the textfield back.

Why I can not put another component in the original cell after the textfield is removed??

[Craig Wood]

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
 
public class GridBagTest implements ActionListener
{
    JTextField textField;
    JPanel panel;
    int count = 0;
 
    public void actionPerformed(ActionEvent e)
    {
        Component c = panel.getComponent(2);
        GridBagLayout layout = (GridBagLayout)panel.getLayout();
        GridBagConstraints gbc = layout.getConstraints(c);
        panel.remove(c);
        if(c == textField)
        {
            JButton button = new JButton("button " + ++count);
            layout.setConstraints(button, gbc);
            panel.add(button, 2);
        }
        else
        {
            layout.setConstraints(textField, gbc);
            panel.add(textField, 2);
        }
        panel.revalidate();
        panel.repaint();
    }
 
    private JPanel getContent()
    {
        textField = new JTextField("swap me", 12);
        panel = new JPanel(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.insets = new Insets(2,2,2,2);
        gbc.weightx = 1.0;
        gbc.weighty = 1.0;
        gbc.gridwidth = GridBagConstraints.RELATIVE;
        panel.add(new JLabel("label 1"), gbc);
        gbc.gridwidth = GridBagConstraints.REMAINDER;
        panel.add(new JLabel("another label"), gbc);
        gbc.gridwidth = GridBagConstraints.RELATIVE;
        panel.add(textField, gbc);
        gbc.gridwidth = GridBagConstraints.REMAINDER;
        panel.add(new JButton("another button"), gbc);
        return panel;
    }
 
    private JPanel getControl()
    {
        JButton button = new JButton("swap components");
        button.addActionListener(this);
        JPanel panel = new JPanel();
        panel.add(button);
        return panel;
    }
 
    public static void main(String[] args)
    {
        GridBagTest test = new GridBagTest();
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(test.getContent());
        f.getContentPane().add(test.getControl(), "Last");
        f.setSize(300,200);
        f.setLocation(200,200);
        f.setVisible(true);
    }
}

[Jerry Crothers]

Geez after I added:

panel.revalidate();

it worked. Thats annoying. Thanks for the code sample though.