GridBagLayout: Aligning JPanels in one vertical line

Question

Possible Duplicate:
Alignment issue in GridBagLayout

Please have a look at the following code

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

public class TestForm extends JFrame
{
    private JLabel firstLabel, secondLabel, thirdLabel, fourthLabel, fifthLabel;

    private JTextField firstTxt, secondTxt, thirdTxt, fourthTxt, fifthTxt;

    private JPanel centerPanel;
    private JPanel southPanel;
    private JLabel comboLabel;
    private JComboBox percentageCombo;
    private JLabel endTargetLabel;
    private JLabel mustLoseLabel;

    private GridBagLayout mainLayout = new GridBagLayout();
    private GridBagConstraints mainCons = new GridBagConstraints();

      public TestForm()
      {
        //Declaring instance variables  
        firstLabel = new JLabel("First: ");
        secondLabel = new JLabel("Second: ");
        thirdLabel = new JLabel("Third: ");
        fourthLabel = new JLabel("Fourth: ");
        fifthLabel = new JLabel("Fifth: ");        
        comboLabel = new JLabel("Select System Performance: ");

        firstTxt = new JTextField(7);
        secondTxt = new JTextField(7);
        thirdTxt = new JTextField(7);
        fourthTxt = new JTextField(7);
        fifthTxt = new JTextField(7);

        endTargetLabel = new JLabel("Your End Target Performance is: ");
        mustLoseLabel = new JLabel("Sammple Performance You Must Lose: ");  

        percentageCombo = new JComboBox();
        percentageCombo.addItem("No Value is Set");


       this.setLayout(mainLayout);
        mainCons.gridy = 1;
        mainCons.gridx = 1;
        mainCons.anchor = GridBagConstraints.NORTH;
        this.add(createNorthPanel(),mainCons);

        mainCons.anchor = GridBagConstraints.WEST;
        mainCons.gridy = 2;
        mainCons.gridx = 1;
        mainCons.anchor = GridBagConstraints.CENTER;
        mainCons.insets = new Insets(15,0,0,0);
        this.add(createCenterPanel(),mainCons);

        mainCons.anchor = GridBagConstraints.SOUTH;
        mainCons.gridy = 3;
        mainCons.gridx = 1;
        this.add(createSouthPanel(),mainCons);

        this.setTitle("The Test Form");
        this.pack();
        this.setLocationRelativeTo(null);
        this.setVisible(true);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);


    }

    private JPanel createNorthPanel()
    {
        JPanel northPanel = new JPanel();

        northPanel = new JPanel();
        northPanel.setLayout(new FlowLayout());

        JLabel logoLabel = new JLabel();
        logoLabel.setIcon(new ImageIcon(getClass().getResource("/images/TESTING-LOGO.gif")));

        northPanel.add(logoLabel);

        return northPanel;
    }


    private JPanel createCenterPanel()
    {
        centerPanel = new JPanel();

        GridBagLayout gbl = new GridBagLayout();
        GridBagConstraints gbc = new GridBagConstraints();

        centerPanel.setLayout(gbl);

        gbc.gridx = 1;
        gbc.gridy = 1;
        gbc.fill = GridBagConstraints.BOTH;
        gbc.insets = new Insets(15,0,0,0);
        centerPanel.add(firstLabel,gbc);

        gbc.gridx = 2;
        gbc.gridy = 1;
        gbc.fill = GridBagConstraints.BOTH;
        gbc.insets = new Insets(15,0,0,0);
        centerPanel.add(firstTxt,gbc);

        gbc.gridx = 3;
        gbc.gridy = 1;
        gbc.fill = GridBagConstraints.BOTH;
        gbc.insets = new Insets(15,10,0,0);
        centerPanel.add(secondLabel,gbc);

        gbc.gridx = 4;
        gbc.gridy = 1;
        gbc.fill = GridBagConstraints.BOTH;
        gbc.insets = new Insets(15,-10,0,0);
        centerPanel.add(secondTxt,gbc);

        gbc.gridx = 1;
        gbc.gridy = 2;
        gbc.fill = GridBagConstraints.BOTH;
        gbc.insets = new Insets(15,0,0,0);
        centerPanel.add(thirdLabel,gbc);

        gbc.gridx = 2;
        gbc.gridy = 2;
        gbc.fill = GridBagConstraints.BOTH;
        gbc.insets = new Insets(15,0,0,0);
        centerPanel.add(thirdTxt,gbc);

        gbc.gridx = 3;
        gbc.gridy = 2;
        gbc.fill = GridBagConstraints.BOTH;
        gbc.insets = new Insets(15,10,0,0);
        centerPanel.add(fourthLabel,gbc);

        gbc.gridx = 4;
        gbc.gridy = 2;
        gbc.fill = GridBagConstraints.BOTH;
        gbc.insets = new Insets(15,-10,0,0);
        centerPanel.add(fourthTxt,gbc);

        gbc.gridx = 5;
        gbc.gridy = 2;
        gbc.fill = GridBagConstraints.BOTH;
        gbc.insets = new Insets(15,7,0,0);
        centerPanel.add(fifthLabel,gbc);

        gbc.gridx = 6;
        gbc.gridy = 2;
        gbc.fill = GridBagConstraints.BOTH;
        gbc.insets = new Insets(15,5,0,0);
        centerPanel.add(fifthTxt,gbc);

        centerPanel.setBorder(BorderFactory.createTitledBorder("The Testing Form"));
        centerPanel.validate();

        return centerPanel;

    }


     private JPanel createSouthPanel()
    {
        southPanel = new JPanel();

        GridBagLayout gbl = new GridBagLayout();
        GridBagConstraints gbc = new GridBagConstraints();

        southPanel.setLayout(gbl);

        gbc.gridx = 1;
        gbc.gridy = 1;
        gbc.fill = GridBagConstraints.BOTH;
        gbc.insets = new Insets(15,0,0,0);
        southPanel.add(comboLabel,gbc);

        gbc.gridx = 2;
        gbc.gridy = 1;
        gbc.fill = GridBagConstraints.BOTH;
        gbc.insets = new Insets(15,5,0,0);
        southPanel.add(percentageCombo,gbc);

        gbc.gridx = 1;
        gbc.gridy = 2;
        gbc.fill = GridBagConstraints.BOTH;
        gbc.insets = new Insets(10,0,0,0);
        southPanel.add(endTargetLabel,gbc);


        gbc.gridx = 1;
        gbc.gridy = 3;
        gbc.fill = GridBagConstraints.BOTH;
        gbc.insets = new Insets(10,0,0,0);
        southPanel.add(mustLoseLabel,gbc);

        southPanel.setBorder(BorderFactory.createTitledBorder("See Your End Target "));

        return southPanel;
    }

    public static void main(String[]args)
    {
        try
        {
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
            new TestForm();
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
    }
}

This is what I get when I use this code

But, I need the following

1. Both southPanel and centerPanel should appear in a one vertical line. In here, the southPanel is not in the same line as centerPanel, it is bit more aligned to the right
2. Both Panels should move left a bit (showed in image)
3. Both Panels should have the same size
4. The size of the panels are too small. They should be bit large than now, while not changing the spaces and alignments to its components.

If you know the answer for at least one question, please help. I am attaching the logo as well.

Note: Removing more elements from the code will not generate the original issue. That is why this code is bit big.

Answer 1

You need to assign more "weight" to each of the panels, which will force them to align within the given space.

this.setLayout(mainLayout);
mainCons.gridy = 1;
mainCons.gridx = 1;
mainCons.anchor = GridBagConstraints.NORTHWEST;
mainCons.weightx = 1;
this.add(createNorthPanel(), mainCons);

mainCons.anchor = GridBagConstraints.WEST;
mainCons.weightx = 1;
mainCons.gridy = 2;
mainCons.gridx = 1;
mainCons.insets = new Insets(15, 0, 0, 0);
this.add(createCenterPanel(), mainCons);

mainCons.anchor = GridBagConstraints.SOUTHWEST;
mainCons.weightx = 1;
mainCons.gridy = 3;
mainCons.gridx = 1;
this.add(createSouthPanel(), mainCons);

As a side node, you can actually use the same instance of the GridBagConstraints and change only those values you need, which make you code a little easier to read (not to mention reduce the amount you need to type ;))

You might like to take a look at How to use GridBagLayout