Question

I’ve a mainPanel with VerticalLayout (org.jdesktop.swingx.VerticalLayout). main panel has several sub panels. One of them is a dynamically changing panel according to the user selection. So, I’ve set it’s layout as CardLayout which I think is the easiest (maybe best?) way to achieve that.

I’ll call that panel elasticPanel. As the name says, it should be elastic. Which means, it should be capable of both expanding and contracting. Let’s say it behave like this. If the user select 1, the elasticPanel should display one , say, JComboBox. If the user select 2 then, two JComboBoxs…

Ok, it works perfectly up to now. Now the user select 1 again when the elasticPanel is showing two JComboBoxs. What i need to happen now is the elasticPanel should display one JComboBox with it’s normal size. But since the elasticPanel is already expanded, what happens is it shows the JComboBox stretched to fit it’s size. So it gives a weird look.

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Following screenshots show the problem i’m having with my interface.

Before the selection. NONE is selected.

An element is selected

NONE is selected again

I need the elasticPanel (Location of Fault) in the last screenshot to be as in the first screenshot. This is just a simple case. Imagine the look when going back to NONE after displaying about 5, 6 sub components.

I’ve tried the setSize() method. It doesn’t do anything..So how to fix the issue?

Any help is appreciated. Thanks!

Answer 1

It’s hard to tell you are referring CardLayout to what thingy. Since CardLayout works in a different way. What you can do is simply place one JPanel say basePanel having GridLayout(0, 1) and place this JPanel on top of another JPanel say contentPanel, and now set this as the content pane for the JFrame and calling pack() when you add or remove an element from the view. Here is one example showing you what I mean.

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

public class ElasticPanel
{
    private JFrame frame;
    private JPanel contentPane;
    private JPanel basePanel;
    /*
     * Array to hold the JComboBox
     * elements.
     */
    private JComboBox[] prodCombo;  
    private JComboBox[] temp;
    /* 
     * Counter to keep track
     * of the number of JComboBox 
     * present.
     */
    private int counter;  
    /*
     * Data for each JComboBox
     */
    private String[] data = {
                                "None",
                                "Sub Category"
                            };

    private ActionListener comboAction =
            new ActionListener()
    {
        @Override
        public void actionPerformed(ActionEvent ae)
        {
            JComboBox cbox = (JComboBox) ae.getSource();
            String command = (String) ae.getActionCommand();
            int index = Integer.parseInt(command);
            String selection = (String) cbox.getSelectedItem();

            if (selection.equals("None"))
            {
                /*
                 * i = index + 1, because, we want to
                 * remove all JComboBox after this one.
                 */
                for (int i = (index + 1); i < prodCombo.length; i++)
                {
                    temp = new JComboBox[prodCombo.length];
                    for (int j = 0; j < prodCombo.length; j++)
                        temp[j] = prodCombo[j];
                    basePanel.remove(prodCombo[i]); 
                }
                prodCombo = new JComboBox[index + 1];
                for (int i = 0; i <= index; i++)
                {                   
                    prodCombo[i] = temp[i];
                }
                counter = prodCombo.length;
                System.out.println("Item Removed\nCounter : " + counter);
            }
            else if (selection.equals("Sub Category"))
            {
                counter++;
                temp = new JComboBox[counter];
                for (int i = 0; i < prodCombo.length; i++)
                {
                    temp[i] = prodCombo[i];
                }
                temp[counter - 1] = new JComboBox(data);
                temp[counter - 1].setActionCommand("" + (counter - 1));
                temp[counter - 1].addActionListener(this);
                prodCombo = new JComboBox[counter];
                for (int i = 0; i < counter; i++)
                    prodCombo[i] = temp[i];
                basePanel.add(prodCombo[counter - 1]);  
                System.out.println("Item Added\nCounter : " + counter);
            }

            //basePanel.revalidate();
            //basePanel.repaint();
            frame.pack();
        }
    };

    public ElasticPanel()
    {
        prodCombo = new JComboBox[1];
        counter = 1;
    }

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

        contentPane = new JPanel();

        basePanel = new JPanel(new GridLayout(0, 1, 5, 5));

        prodCombo[counter - 1] = new JComboBox(data);
        prodCombo[counter - 1].setActionCommand("" + (counter - 1));
        prodCombo[counter - 1].addActionListener(comboAction);

        basePanel.add(prodCombo[counter - 1]);
        contentPane.add(basePanel);

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

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

*Latest Update : *

More insight by adding more components and placing the elastic panel at some other location, and not on top of content pane.

import java.awt.*;
import java.awt.event.*;
import java.net.MalformedURLException;
import java.net.URL;
import javax.swing.*;

public class VirtualViewGUI extends JFrame
{
    private JPanel rightPanel;
    private ElasticPanel elasticPanel;

    public VirtualViewGUI()
    {
        super("Virtual View");

        JMenuBar jmenuBar = new JMenuBar();
        JMenu fileMenu = new JMenu("File");
        JMenu helpMenu = new JMenu("Help");
        JMenu feel = new JMenu("Look & Feel");

        JMenu layOutMenu = new JMenu("ConfigureCells");
        JMenuItem add_files = new JMenuItem("Select Directory.."); 
        JMenuItem minCellSize = new JMenuItem("height 260 X  width 260"); 
        JMenuItem moderateCellSize = new JMenuItem("height 320 X  width 320"); 
        JMenuItem maxCellSize = new JMenuItem("height 360 X  width 360"); 
        JMenuItem exit = new JMenuItem("Exit");
        JMenuItem help = new JMenuItem("Help Content");

        fileMenu.add(add_files);
        fileMenu.add(exit);
        layOutMenu.add(minCellSize);
        layOutMenu.add(moderateCellSize);
        layOutMenu.add(maxCellSize);
        helpMenu.add(help);

        jmenuBar.add(fileMenu);
        jmenuBar.add(layOutMenu);
        jmenuBar.add(helpMenu);

        ImageIcon myImage = null;
        try
        {
            myImage = new ImageIcon(
                new URL("http://gagandeepbali.uk.to/" + 
                        "gaganisonline/images/swing/" + 
                        "stackoverflow/cow-cartoon.jpg"));
        }
        catch(MalformedURLException mue)    
        {
            mue.printStackTrace();
        }

        JLabel icon = new JLabel(myImage);
        icon.setIcon(myImage);
        setJMenuBar(jmenuBar); 

        rightPanel = new JPanel();
        elasticPanel = new ElasticPanel(this);
        rightPanel.add(elasticPanel);

        JPanel contentPane = new JPanel();
        contentPane.setLayout(new BorderLayout(5, 5));
        contentPane.add(icon, BorderLayout.CENTER);
        contentPane.add(rightPanel, BorderLayout.LINE_END);

        setContentPane(contentPane);
        pack();
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationByPlatform(true);    
        setVisible(true);
        System.out.println("File Separator is : " + System.getProperty("file.separator"));
    }

    public static void main(String... args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {
                new VirtualViewGUI();
            }
        });
    }
}

class ElasticPanel extends JPanel
{
    private JFrame frame;
    private JPanel contentPane;
    /*
     * Array to hold the JComboBox
     * elements.
     */
    private JComboBox[] prodCombo;  
    private JComboBox[] temp;
    /* 
     * Counter to keep track
     * of the number of JComboBox 
     * present.
     */
    private int counter;  
    /*
     * Data for each JComboBox
     */
    private String[] data = {
                                "None",
                                "Sub Category"
                            };

    private ActionListener comboAction =
            new ActionListener()
    {
        @Override
        public void actionPerformed(ActionEvent ae)
        {
            JComboBox cbox = (JComboBox) ae.getSource();
            String command = (String) ae.getActionCommand();
            int index = Integer.parseInt(command);
            String selection = (String) cbox.getSelectedItem();

            if (selection.equals("None"))
            {
                /*
                 * i = index + 1, because, we want to
                 * remove all JComboBox after this one.
                 */
                for (int i = (index + 1); i < prodCombo.length; i++)
                {
                    temp = new JComboBox[prodCombo.length];
                    for (int j = 0; j < prodCombo.length; j++)
                        temp[j] = prodCombo[j];
                    remove(prodCombo[i]);   
                }
                prodCombo = new JComboBox[index + 1];
                for (int i = 0; i <= index; i++)
                {                   
                    prodCombo[i] = temp[i];
                }
                counter = prodCombo.length;
                System.out.println("Item Removed\nCounter : " + counter);
            }
            else if (selection.equals("Sub Category"))
            {
                counter++;
                temp = new JComboBox[counter];
                for (int i = 0; i < prodCombo.length; i++)
                {
                    temp[i] = prodCombo[i];
                }
                temp[counter - 1] = new JComboBox(data);
                temp[counter - 1].setActionCommand("" + (counter - 1));
                temp[counter - 1].addActionListener(this);
                prodCombo = new JComboBox[counter];
                for (int i = 0; i < counter; i++)
                    prodCombo[i] = temp[i];
                add(prodCombo[counter - 1]);    
                System.out.println("Item Added\nCounter : " + counter);
            }

            //revalidate();
            //repaint();
            frame.pack();
        }
    };

    public ElasticPanel(JFrame frame)
    {
        this.frame = frame;
        prodCombo = new JComboBox[1];
        counter = 1;

        setLayout(new GridLayout(0, 1, 5, 5));

        prodCombo[counter - 1] = new JComboBox(data);
        prodCombo[counter - 1].setActionCommand("" + (counter - 1));
        prodCombo[counter - 1].addActionListener(comboAction);

        add(prodCombo[counter - 1]);        
    }
}