Change Image in JFrame?

Question

I've been working through the Oracle tutorial for images this one here:

import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.io.*;
import javax.imageio.*;
import javax.swing.*;

public class LoadImageApp extends Component {

    BufferedImage img;

    public void paint(Graphics g) {
        g.drawImage(img, 0, 0, null);
    }

    public LoadImageApp() {
       try {
           img = ImageIO.read(new File("strawberry.jpg"));
       } catch (IOException e) {
       }

    }

    public Dimension getPreferredSize() {
        if (img == null) {
             return new Dimension(100,100);
        } else {
           return new Dimension(img.getWidth(null), img.getHeight(null));
       }
    }

    public static void main(String[] args) {

        JFrame f = new JFrame("Load Image Sample");

        f.addWindowListener(new WindowAdapter(){
                public void windowClosing(WindowEvent e) {
                    System.exit(0);
                }
            });

        f.add(new LoadImageApp());
        f.pack();
        f.setVisible(true);
    }
}

I want to change the image that appears in the JFrame. If I say:

f.add(new LoadImageApp());      
f.revalidate();
f.repaint();

The new image will appear, behind the current one. What I'd like to do is remove the previous image and replace, but I can't work out how I'd go about doing this with this snippet of code?

Answer 1

Why don't you just use a JLabel to display the image? Then to change the image you just invoke the setIcon(...) method.

If you do need to do custom painting then:

1. For a Swing application you should extend JComponent, not Component

2. You should be overriding paintComponent(), not paint()

3. If you want to change the image then create a method like setImage() to change the image. Then in that method you invoke repaint() to force the component to repaint itself. There is no need to create a new component and replace the component on the GUI.