Showing preview of downloaded pis fails

Question

Hi there (second try),
this is a often discussed matter AFAIK. There are synchronizing Problems when downloading pics into a component that displays the pics. This could be solved by using imageObservers or MediaTracker Objects (I tried them, but they didn't work).
So far. In my application I have a different way of retrieving pictures. First I read in a jpg-File via a DataInputStream and write it directly to the harddisk. then I open the file and put it in a JLabel for previewing. The Streamreading and the displaying are obviously unsynchronous.
What I want is: Reading one File. Displaying it. Reading the next File. Display it etc. etc.
What I get is: Reading, Reading, Reading, Displaying the last file.
How can I handle this ? Is there a way to wait until the File is completley downloaded, display then the picture and start then to download the next pic?
Below you find a listing of a reduced version of my app (it has unfortunatly still around 200 lines, but if you ignore that swing stuff in the constructor, the real code is short enough.). Its fully working if you want to try it (before starting: copy any jpg named "title.jpg" into the same dir. make sure the workDir (Line 20) exists).
In the listing you will find methods that are responsible for downloading and displaying the Pics. These Methods are not too long.
they are called:
public void getAllPics() as a controlling method
public void getThePic() for really downloading a pic
public void showThePic() for Displaying the Pic in the JLabel
Thanks
- rebelman
Here is the Listing:
*  ProblemApp
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import java.io.*;
import java.net.*;
import java.util.Vector;
public class ProblemApp extends JFrame {
     JCheckBox           previewBox;
     JLabel               previewLabel;
     JButton               browseButton, exitButton;
     JTextArea           myLogArea;
     JScrollPane      myLogScrollPane;
     JScrollPane          previewPane;
     String workDir = "c:\\";
     public ProblemApp() {                                             // **** Constructor
          super("Housten, we have a problem!");
          getContentPane().setLayout(new BorderLayout());
          // Preparing Button Area
          browseButton                     = new JButton("Start   Download");
          exitButton                          = new JButton("Exit Application");
          // Preparing logging area
          myLogArea                          = new JTextArea("Log:", 6, 40);
          myLogArea.setLineWrap(true);                    // Wordwrap on
          myLogArea.setWrapStyleWord(true);               // Wrap on word borders
          myLogArea.setEditable(false);                    // not editable
          myLogScrollPane                = new JScrollPane(myLogArea);
          // Preparing Preview Area
          previewBox                          = new JCheckBox("Preview on");
          previewBox.setMnemonic(KeyEvent.VK_P);
          previewBox.setSelected(true);
          previewLabel                    = new JLabel(new ImageIcon("title.jpg", "titlepic"));
          previewPane                         = new JScrollPane(previewLabel);
          // Defining panels
          JPanel topPanel                    = new JPanel();
          JPanel middlePanel               = new JPanel();
          JPanel bottomPanel                = new JPanel();
          JPanel browseButtonPanel     = new JPanel();
          JPanel exitButtonPanel          = new JPanel();
          JPanel previewPanel               = new JPanel();
          JPanel picPanel                    = new JPanel();
          // Defining Layoutmanagers for Panels
          topPanel.setLayout(new GridLayout(1,2));                               // top Panel for Upper Panels
          middlePanel.setLayout(new BorderLayout());                               // middle Panel for middle Panels
          bottomPanel.setLayout(new BorderLayout());                               // bottom panel for logging
          browseButtonPanel.setLayout(new FlowLayout(FlowLayout.CENTER));     // Panel for browseButt (for width)
          exitButtonPanel.setLayout(new FlowLayout(FlowLayout.CENTER));     // Panel for exit Butt (for width)
          picPanel.setLayout(new GridLayout(1,1));                               // pic panel for the pic
          previewPanel.setLayout(new FlowLayout(FlowLayout.LEFT));          // Panel for the Preview Box
          // Adding components to panels
          browseButtonPanel.add(browseButton);
          exitButtonPanel.add(exitButton);
          picPanel.add(previewPane);
          previewPanel.add(previewBox);
          topPanel.add(browseButtonPanel);
          topPanel.add(exitButtonPanel);
          middlePanel.add(previewPanel, BorderLayout.NORTH);
          middlePanel.add(picPanel, BorderLayout.CENTER);
          bottomPanel.add(myLogScrollPane);
          // adding panels to frame
          getContentPane().add(topPanel, BorderLayout.NORTH);
          getContentPane().add(middlePanel, BorderLayout.CENTER);
          getContentPane().add(bottomPanel, BorderLayout.SOUTH);
          this.enableEvents(AWTEvent.WINDOW_EVENT_MASK);                    // enabling events (window closing)
          // ActionListener for Start Download Button
          browseButton.addActionListener(new ActionListener() {          // anonymous Class for start Download
               public void actionPerformed(ActionEvent e) {
                    getAllPics();                                                  // calling method below
          // Action Listner, for exiting the Application
          ActionListener exitListener = new ActionListener() {           // anonymous Class exitListener
               public void actionPerformed(ActionEvent e) {
                    dispose();
                    System.exit(0);
          exitButton.addActionListener(exitListener);                         // Register exitListener to Exitbutton
     }                                                                                // **** end of Constructor
     //Method for downloading all the pics
     // The caller for getAllPics must make sure, that the workDir allready exists
     public void getAllPics() {
          String theFilename;
          String myURL;
          Vector theList = new Vector(4,4);
          theList = getList();                                        // Trying to get a list of picture URL's
          for(int i = 0; i < theList.size() ; i++) {
               myURL = theList.elementAt(i).toString();
               if(myURL.toLowerCase().endsWith(".jpg")) {          // its a JPG: No problem, get it!
                    theFilename = workDir+"pic"+i+".jpg";          // workDir defined above. make sure it exists
                    getThePic(myURL, theFilename);                    // really getting a pic now
                    showThePic(theFilename);                         // Displaying the preview
               else {
                    addLine("This is not a JPG. Trying this later. ");
                    addLine(myURL);
     // Method for downloading a pic when I know its URL and a valid Path icl. pic-filename
     public void getThePic(String theURL, String thePath) {               //complete URL of the PIC, and complete path
          byte thisByte;
          DataOutputStream picFile =null;
          try {
               URL myURL = new URL(theURL);
               try {
                    DataInputStream myPic = new DataInputStream(myURL.openStream());
                    picFile = makeOutputFile(thePath);               // getting output-stream
                    try {
                         addLine("Read: "+theURL);
                         while (true) {
                              thisByte = (byte)myPic.readByte();
                              picFile.writeByte(thisByte);
                    catch(EOFException e){ // File complete
               catch(Exception e) {
                    addLine("Error while reading the pic!");
          catch(MalformedURLException mue) {
               addLine("Error in the URL!");
          finally {
               try {
                    picFile.flush();
                    picFile.close();
                    addLine("Saved as: "+thePath);
               catch(IOException e){
     } // end of method getThePic()
     // Method for showing the given Pic
     public void showThePic(String thePath) {
          if(previewBox.isSelected())
               previewLabel.setIcon(new ImageIcon(thePath));
     // Method for the Pic Saver, that creates the outputstream
     public DataOutputStream makeOutputFile(String thePath) {
          FileOutputStream fileOut =null;
          try {
               fileOut = new FileOutputStream(thePath);     // give it the path, INCLUDING the filename
          catch(IOException e){
               addLine("Error while creating the output file!");
          return new DataOutputStream(fileOut);
     //Method for creating a URL List in a Vector
     public Vector getList() {
          Vector theList = new Vector(4,4);
          theList.addElement("http://user.cs.tu-berlin.de/~karlb/tux/sysadminsparadise.jpg");
          theList.addElement("http://user.cs.tu-berlin.de/~karlb/tux/tuxblackbig.jpg");
          theList.addElement("http://user.cs.tu-berlin.de/~karlb/tux/Toasted.jpg");
          theList.addElement("http://www.apple.com/hotnews/features/mwsf99pics/lara.jpg");
          theList.addElement("http://www.empireonline.co.uk/img/features/events/tombraider/premiere/lara.jpg");
          return theList;
     // Method for appending Logmessages to the log area
     public void addLine(String newLine) {
          myLogArea.append("\n" + newLine);
          JViewport vp = myLogScrollPane.getViewport();
          int height = Math.max(0, this.getSize().height - vp.getHeight());
          vp.scrollRectToVisible(new Rectangle(0, height, vp.getWidth(), vp.getHeight()));
     public static void main(String[] arg) {                                                       //Mainmethod
           ProblemApp myWindow = new ProblemApp();
           myWindow.pack();
           myWindow.show();
}

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