制作面板的背景图像时遇到麻烦

Question

I am trying to add a background image to a JPanel. The paint Component doesn't seem to paint the image imported for the background . Could anyone point out why? I have imported all the necessary libraries.

public class ImagePanel  extends JPanel {
    public static BufferedImage image;

    public ImagePanel() {
        try {
            image = ImageIO.read(new File("cards/background.png"));
            System.out.println("Image Import Succesful");
        } catch (IOException ex) {
            System.out.println("IMAGE IMPORT ERROR");
        }
        ImageIcon icon = new ImageIcon(image);
        icon.setImage(image);
        JLabel imageLabel = new JLabel(icon);
        add(imageLabel);

    }


    @Override
    protected void paintComponent(Graphics g) {
        System.out.println("painted");
        super.paintComponent(g);
        g.drawImage(image, 100, 100,
                    this); 
    }
}

Answer 1

Where are you loading your image from? A file system or classpath ?

If you are loading you image from classpath you can use the class loader to load the image.If you are loading the image from a file system the path to that file has to be an absolute path.

You can paint the background of a panel if you are loading the image from classpath like this:

public class ImagePanel  extends JPanel {

   private ImageIcon imageIcon;

    public ImagePanel() {
       prepareBackground();
    }

    @Override
    protected void paintComponent(Graphics g) {
           super.paintComponent(g);
           if (null!= imageIcon)
               g.drawImage(image.getImage(), 100, 100, this);
           else
               System.err.println("Background image is NULL!!");
        }
    }

    private void prepareBackground() {
        final java.net.URL imgURL = ImagePanel.class.getResource("cards/background.png");
        imageIcon = new ImageIcon(imgURL);
    }
}

If you are loading from a file system , you can correct your code here:

image = ImageIO.read(new File("COMPLETE_PATH_TO_background.png"));