Java Set Layout

Question

I need to create a JFrame which has three JPanels laid out as shown:

Could anybody please tell me how I can achieve this layout? I have already tried using BorderLayout, but in BorderLayout, if I add the topmost pane at BorderLayout.NORTH, the one in the center at BorderLayout.CENTER, and the one at the bottom to BorderLayout.SOUTH, the topmost pane becomes too small (in height) and the pane in the center becomes too big (in height).

P.S. I have already made the 3 panes and set their preferred sizes properly.

Answer 1

You could use all sorts of things, compound layouts (using two BorderLayouts for example) or other layouts, it will depend on what you ultimately want to achieve.

For simplicity, I'd use a GridBagLayout, for example...

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class TestLayout {

    public static void main(String[] args) {
        new TestLayout();
    }

    public TestLayout() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridwidth = GridBagConstraints.REMAINDER;
            gbc.weightx = 1;
            gbc.weighty = 1;
            gbc.fill = GridBagConstraints.BOTH;

            add(new ABigPanel(), gbc);

            gbc.weighty = 0;
            gbc.fill = GridBagConstraints.HORIZONTAL;

            add(new ASmallPanel(), gbc);
            add(new ASmallerPanel(), gbc);
        }

    }

    public class ABigPanel extends JPanel {

        public ABigPanel() {
            setBackground(Color.RED);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(400, 200);
        }

    }

    public class ASmallPanel extends JPanel {

        public ASmallPanel() {
            setBackground(Color.GREEN);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 180);
        }

    }

    public class ASmallerPanel extends JPanel {

        public ASmallerPanel() {
            setBackground(Color.CYAN);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 40);
        }

    }

}

See How to Use GridBagLayout for more details