Java GUI create three JPanel in one JFrame

Question

I have a problem with Java GUI.

I want to create three JPanel instances which have size different in one JFrame . JFrame size 300x800 and Panel1 300x200, Panel2 300x100 and Panel3 300x500. I want to add this panels under by under.

How to solve this problem?

Answer 1

Use a BorderLayout ¹ .

• Add panel1 to the NORTH
• Add panel2 to the CENTER
• Add panel3 to the SOUTH

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EG

Stretch your imagination that the heights are ten times bigger.

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

class ColoredPanels {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                JPanel gui = new JPanel(new BorderLayout(3,3));
                gui.setBackground(Color.BLUE);
                gui.setBorder(new EmptyBorder(5,5,5,5));

                JPanel panel1 = new JPanel();
                panel1.setPreferredSize(new Dimension(300,20));
                panel1.setBackground(Color.RED);
                gui.add(panel1, BorderLayout.NORTH);

                JPanel panel2 = new JPanel();
                panel2.setPreferredSize(new Dimension(300,10));
                panel2.setBackground(Color.ORANGE);
                gui.add(panel2, BorderLayout.CENTER);

                JPanel panel3 = new JPanel();
                panel3.setPreferredSize(new Dimension(300,50));
                panel3.setBackground(Color.YELLOW);
                gui.add(panel3, BorderLayout.SOUTH);

                // a frame would need pack() etc.
                JOptionPane.showMessageDialog(null, gui);
            }
        });
    }
}

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BTW

1. Use BorderLayout , .. or BoxLayout as mentioned by Shakedown.
2. The panels as described will not fit into the frame at that size. A frame has its own decorations to account for (title bar, menus, borders etc.)
3. Please use camelCase for attribute names.

Answer 2

You can try sizing your panels with setPreferredSize() and company. Then look into using a BoxLayout on your frame, which will put your panels in a row or column.