How to Create a Fullscreen Window with Transparency in Java

Question

How can I create a fullscreen window with transparency using Java?

// Example Java code to create a transparent fullscreen window
import javax.swing.*;
import java.awt.*;

public class TransparentFullScreen {
    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.setUndecorated(true); // Remove window borders
        frame.setExtendedState(JFrame.MAXIMIZED_BOTH); // Fullscreen

        // Set transparency color
        frame.setBackground(new Color(0, 0, 0, 0)); // Set background to be transparent

        JPanel panel = new JPanel();
        panel.setOpaque(false); // Make JPanel transparent

        frame.add(panel);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

Answer

In Java, creating a fullscreen window with transparency involves several steps: removing window decorations, maximizing the window size, and setting the background color to be transparent. Here’s how to do it effectively using the Swing framework.

// Example Java code to create a transparent fullscreen window
import javax.swing.*;
import java.awt.*;

public class TransparentFullScreen {
    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.setUndecorated(true); // Remove window borders
        frame.setExtendedState(JFrame.MAXIMIZED_BOTH); // Fullscreen

        // Set transparency color
        frame.setBackground(new Color(0, 0, 0, 0)); // Set background to be transparent

        JPanel panel = new JPanel();
        panel.setOpaque(false); // Make JPanel transparent

        frame.add(panel);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

Causes

The default JFrame has decorations (like title bar), which we need to remove for fullscreen mode.
Setting the background color to transparent requires proper configuration of the window and its components.

Solutions

Use JFrame.setUndecorated(true) to remove window decorations.
Maximize the window using JFrame.setExtendedState(JFrame.MAXIMIZED_BOTH).
Set the background color of the JFrame and its components to be transparent by using new Color(0, 0, 0, 0) and setting components to non-opaque.

Common Mistakes

Mistake: Forgot to set the frame as undecorated, resulting in a standard window border.

Solution: Use frame.setUndecorated(true) before setting the frame visible.

Mistake: Not setting the JPanel to non-opaque leads to the window showing a colored background instead of being transparent.

Solution: Use panel.setOpaque(false) to allow transparency.

Helpers

Java fullscreen
transparent window Java
Java Swing transparency
create transparent window Java
fullscreen Java example