How to Make a Java Panel Fullscreen?

What are the steps to make a Java panel display in fullscreen mode?

public class FullscreenExample extends JFrame {
    public FullscreenExample() {
        // Set up the JFrame
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setUndecorated(true); // Remove title bar
        setExtendedState(JFrame.MAXIMIZED_BOTH); // Maximize window
        // Create panel
        JPanel panel = new JPanel();
        panel.setBackground(Color.BLUE); // Example panel color
        add(panel);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            FullscreenExample example = new FullscreenExample();
            example.setVisible(true);
        });
    }
}

Creating a fullscreen panel in Java using Swing requires a few simple steps. By making your JFrame undecorated and maximizing it, you can achieve a fullscreen effect.

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

public class FullscreenExample extends JFrame {
    public FullscreenExample() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setUndecorated(true);
        setExtendedState(JFrame.MAXIMIZED_BOTH);
        JPanel panel = new JPanel();
        panel.setBackground(Color.BLUE);
        add(panel);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            FullscreenExample example = new FullscreenExample();
            example.setVisible(true);
        });
    }
}

Causes

• The default JFrame settings include a title bar and borders, which are not suitable for fullscreen applications.
• Panels need to be added to a fullscreen JFrame for visibility.

Solutions

• Use `setUndecorated(true)` to remove the title bar and window borders.
• Call `setExtendedState(JFrame.MAXIMIZED_BOTH)` to maximize the window across the entire screen.
• Ensure that the panel component is added to the JFrame before making it visible.

Mistake: Forgetting to call `setUndecorated(true)` before setting the JFrame visible, leading to a normal window appearance.

Solution: Make sure to set the undecorated property before showing the window.

Mistake: Not adding the panel to the JFrame before calling `setVisible(true)`, which results in a blank window.

Solution: Always add the panel to the JFrame within the constructor before making it visible.