How do I display a BufferedImage in a JComponent?

Question

I have been trying this for hours now. I have a class that extends JComponent, and in its paintComponent I am trying to draw an image, but I am not being able to. Here is my code:

public class Main extends JComponent{



public static void main(String[] args) {

    Main main = new Main();

    JFrame frame = new JFrame(Info.getGameTitle());
    frame.add(main);

    frame.setSize(Info.getWidth(), Info.getHeight());
    frame.setResizable(false);

    frame.addWindowListener(new WindowAdapter(){
        public void windowClosing(WindowEvent e){
            System.out.println("Window closed");
            System.exit(0);
        }
    });

    frame.setAlwaysOnTop(true);
    frame.setFocusable(true);
    frame.setAutoRequestFocus(true);
    frame.setLocationRelativeTo(null);

    frame.setVisible(true);

    Graphics g = main.getGraphics();

    main.paint(g);


}

public void paintComponent(Graphics g) {
    super.paintComponent(g);

    BufferedImage image = null;
    try {
        image = ImageIO.read(new FileInputStream("images/01.jpg"));
    }catch(FileNotFoundException e) {
        System.out.println("Could not find file!");
        e.printStackTrace();
    }catch(IOException e) {
        System.out.println("Could not read file!");
        e.printStackTrace();
    } 

    g.drawImage(image, 0, 0, this);


    }
}

It is not throwing any exceptions, so the image appears to be loaded. However, nothing appears on the screen. If I try to draw shapes or text, that works fine. What am I doing wrong?

EDIT: Now I have supplied a working example.

Answer 1

Graphics g = main.getGraphics();
main.paint(g);

No, no, no, NO, NO! A infinite times NO! This is not how painting works!

Take a look at Performing Custom Painting and Painting in AWT and Swing for a better understanding of how painting works in Swing.

getGraphics can return null and will only return the last used context to paint the component, anything painted to it will be erased on the next paint cycle.

There is never a good reason to call paint manually, just don't do it.

You should be do something more along the lines of

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.FileInputStream;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private BufferedImage img = null;

        public TestPane() {
            try {
                img = ImageIO.read(new FileInputStream("..."));
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }

        @Override
        public Dimension getPreferredSize() {
            return img == null ? new Dimension(200, 200) : new Dimension(img.getWidth(), img.getHeight());
        }

        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            if (img != null) {
                g2d.drawImage(img, 0, 0, this);
            }
            g2d.dispose();
        }

    }
}

If your image is still not showing up, I suspect that the image is misplaced.

new FileInputStream("images/01.jpg")

suggests that the image resides within the current directory from where the program is been executed, this is not always the same as where the program resides.

You can use System.getProperty("user.dir") to determine the current "working" directory and compare it to where you think the program resides. You can also use File#exists to test if the file exists or not, although, I would have expected the code to throw an IOException if that were the case.

A better long term solution would be to embedded the image within application (typically including it in the Jar), this removes the above issues.

In that case you'd need to use...

ImageIO.read(getClass().getResource("/images/01.jpg"));

to load the image

Answer 2

Be aware that your JComponent may be painted hundreds of times per second, for example when it is partially obscured by another moving window. So, performance of the paint methods is important, or else you get a "laggy" GUI.

Therefore I suggest to separate the time-consuming part (i.e. reading the image file) from the JComponent.

public class ImageComponent extends JComponent {

    private BufferedImage image;

    public void setImage(final BufferedImage image) {
        this.image = image;
        repaint();
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        if (image != null)
            g.drawImage(image, 0, 0, this);
    }
}

Somewhere else in your code you read the image file and set it into the component:

BufferedImage image = null;
try {
    image = ImageIO.read(new File(fullpathname+"/01.jpg"));
}catch(Exception e) {
    System.out.println("Could not read file!");
    e.printStackTrace();
} 
ImageComponent component = new ImageComponent();
component.setImage(image);

Answer 3

Try this

   BufferedImage image = null;
    try {
        image = ImageIO.read(new File(fullpathname+"/01.jpg"));
    }catch(Exception e) {
        System.out.println("Could not read file!");
        e.printStackTrace();
    } 

public void paintComponent(Graphics g) {
    super.paintComponent(g);


    g.drawImage(image, 0, 0, this);


}

read throws more exceptions

IllegalArgumentException - if input is null.
IOException - if an error occurs during reading.

so catching the more general one (Exception) will cover it

Answer 4

Try this:

Image image = ImageIO.read(new File(file)); g.drawImage(image, 0, 0, this);