Set layout with JPanels

Question

I haven't really worked with Swing at all in Java. I'm experimenting with it. I want to make a set layout that the size can't be changed. I've seen alot of things suggesting to use Layout managers to add multiple JPanels into a JFrame.

However, all the tutorials I've seen involving layout managers say it allows for the user to resize the screen. The layout I want has a rectangle going along the left hand side, a thin rectangle going along the bottom, and a third rectangle taking up the rest of the space. I attempting it using an Absolute layout but it just doesn't want to work for me.

import java.awt.Color;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;


public class Test extends JFrame {

    public Test() {
        JPanel rect1 = new JPanel();
        rect1.setBounds(101, 650, 900, 50);
        rect1.setBackground(Color.RED);
        getContentPane().add(rect1);

        JPanel rect2 = new JPanel();
        rect2.setBounds(0, 650, 100, 1000);
        rect2.setBackground(Color.BLUE);
        getContentPane().add(rect2);

        JPanel rect3 = new JPanel();
        rect3.setBounds(101, 700, 900, 950);
        rect3.setBackground(Color.GREEN);
        getContentPane().add(rect3);

       setTitle("TEST");
       setSize(1000, 700);

       setLocationRelativeTo(null);
       setDefaultCloseOperation(EXIT_ON_CLOSE);        
    }


    public static void main(String[] args) {

        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                Test ex = new Test();
                ex.setVisible(true);
            }
        });
    }
}

Can someone help me properly make three Jpanels in a Jframe in this layout (all with different colors)?

Answer 1

You might be able to achieve the same thing using a BorderLayout as the bases or even a GridBagLayout.

The main piece you are missing is the fact that layout managers use (or can use depending on the layout manager) the component's preferred/minimum/maximum size

Basically, what you would do is define a custom component (extending from something like JPanel) and override it's getPreferredSize method and return the required value you need. Depending on the layout manager, you may also need to override the getMaximumSize and getMinimumSize methods as well.

For example...

Basically, this shows the "default" size and what happens when the screen is resized...

import java.awt.BorderLayout;
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 FixedSizeLayout {

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

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

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                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.gridx = 0;
            gbc.gridy = 0;

            add(new ContentPane(), gbc);
            gbc.gridx++;
            add(new LeftPane(), gbc);
            gbc.gridwidth = 2;
            gbc.gridx = 0;
            gbc.gridy = 1;
            add(new BottomPane(), gbc);

        }

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

    }

    public class ContentPane extends JPanel {

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

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(150, 150);
        }

        @Override
        public Dimension getMinimumSize() {
            return getPreferredSize();
        }

        @Override
        public Dimension getMaximumSize() {
            return getPreferredSize();
        }

    }

    public class BottomPane extends JPanel {

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

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 50);
        }

        @Override
        public Dimension getMinimumSize() {
            return getPreferredSize();
        }

        @Override
        public Dimension getMaximumSize() {
            return getPreferredSize();
        }

    }

    public class LeftPane extends JPanel {

        public LeftPane() {
            setBackground(Color.BLUE);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(50, 150);
        }

        @Override
        public Dimension getMinimumSize() {
            return getPreferredSize();
        }

        @Override
        public Dimension getMaximumSize() {
            return getPreferredSize();
        }

    }
}

Now, if you prefer, you can make the screen non-resizable, but I for one won't like you. I prefer to use the power of the layout managers and allow users to make decisions about how they want to view the content ... where I can ... but that's just me (I don't like non-resizable windows except in the case of some dialogs)