New images not shown

Question

Hi,
Apparently images that are not on the disk when a Java application starts but that are added on disk during program execution, are not shown on JLabels, JButtons, ...
Anyone knows why?
Taaje

Answer 1

Dunno, coz it works 4 me. Y ! 4 u?
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;
import javax.imageio.*;
import javax.swing.*;
public class Example {
    public static void main(String[] args) {
        final File file = new File("temp.jpg"); //constructor doesn't create file in file system, right?
        final JPanel cp = new JPanel(new BorderLayout());
        JButton write = new JButton("write image file");
        write.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent evt) {
                try {
                    URL url = new URL("http://today.java.net/jag/bio/JagHeadshot-small.jpg");
                    ImageIO.write(ImageIO.read(url), "jpg", file);
                } catch (IOException e) {
                    e.printStackTrace();
        JButton read = new JButton("attempt to read file and create label");
        read.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent evt) {
               try {
                   cp.add(new JLabel(new ImageIcon(ImageIO.read(file))));
                   cp.revalidate();
                   cp.repaint();
               } catch (IOException e) {
                   e.printStackTrace();
        JPanel buttons = new JPanel();
        buttons.add(write);
        buttons.add(read);
        cp.add(buttons, BorderLayout.NORTH);
        cp.setPreferredSize(new Dimension(400, 300));
        JFrame f = new JFrame("Example");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setContentPane(cp);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
}