How to set a background image in Java Swing?

In Java Swing, you can set a background image for a window by following these steps:

1. Create a custom class that extends JPanel to display a background image, such as creating a class named BackgroundPanel.

import java.awt.Graphics;
import java.awt.Image;
import javax.swing.ImageIcon;
import javax.swing.JPanel;

public class BackgroundPanel extends JPanel {

    private Image backgroundImage;

    public BackgroundPanel(String imagePath) {
        backgroundImage = new ImageIcon(imagePath).getImage();
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawImage(backgroundImage, 0, 0, getWidth(), getHeight(), this);
    }
}

1. In the main form class, use the BackgroundPanel that was just created as the content panel, and set the background image.

import javax.swing.JFrame;

public class MainFrame extends JFrame {

    public MainFrame() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(800, 600);

        // 创建背景面板并设置背景图片
        BackgroundPanel backgroundPanel = new BackgroundPanel("path/to/image.jpg");
        setContentPane(backgroundPanel);
    }

    public static void main(String[] args) {
        MainFrame frame = new MainFrame();
        frame.setVisible(true);
    }
}

In the above code, the BackgroundPanel class extends JPanel and overrides the paintComponent method to draw a background image. Then, in the constructor of the MainFrame class, a BackgroundPanel object is created and set as the content pane of the window to display the background image.

Please replace “path/to/image.jpg” in the code with the actual path of the background image.