How would I be able to achieve this expandable layout in Java? Flexible BoxLayout etc

Question

I would like to be able to have three JPanels p1 p2 and p3, and have them lay out like so:

I hav

Answer 1

not my favorite LayoutManager, example by using GridBagLayout, easiest could be to use MigLayout, maybe ...

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

public class BorderPanels extends JFrame {

    private static final long serialVersionUID = 1L;

    public BorderPanels() {
        setLayout(new GridBagLayout());// set LayoutManager
        GridBagConstraints gbc = new GridBagConstraints();
        JPanel panel1 = new JPanel();
        Border eBorder = BorderFactory.createEtchedBorder();

        panel1.setBorder(BorderFactory.createTitledBorder(eBorder, "70pct"));
        gbc.gridx = gbc.gridy = 0;
        gbc.gridwidth = gbc.gridheight = 1;
        gbc.fill = GridBagConstraints.BOTH;
        gbc.anchor = GridBagConstraints.NORTHWEST;
        gbc.weightx = gbc.weighty = 70;
        add(panel1, gbc); // add compoenet to the COntentPane

        JPanel panel2 = new JPanel();
        panel2.setBorder(BorderFactory.createTitledBorder(eBorder, "30pct"));
        gbc.gridy = 1;
        gbc.weightx = gbc.weighty = 30;
        gbc.insets = new Insets(2, 2, 2, 2);
        add(panel2, gbc); // add component to the COntentPane

        JPanel panel3 = new JPanel();
        panel3.setBorder(BorderFactory.createTitledBorder(eBorder, "20pct"));
        gbc.gridx =1;
        gbc.gridy = 0;
        gbc.gridwidth = /*gbc.gridheight = */1;
        gbc.gridheight = 2;
        gbc.weightx = /*gbc.weighty = */20;
        gbc.insets = new Insets(2, 2, 2, 2);
        add(panel3, gbc);

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); // important
        pack();
        setVisible(true); // important
    }

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() { // important

            public void run() {
                BorderPanels borderPanels = new BorderPanels();
            }
        });
    }
}

Answer 2

One word: MigLayout. As you have seen, it is possible with the standard layout managers. But I can guarantee you, the layout code would be reduced to 4 lines with MigLayout... (Although it would take you some time to get into MigLayout as it works a bit different than the usual layout managers).