Problem with double buffering

From: David (david.vilanova_at_urbanet.ch)
Date: 11/27/03 

Date: Thu, 27 Nov 2003 20:54:06 +0100

Hello I'm writting an apllication and i like to display and offscreen image.
However my code doesn't seem to work.
It compiles and runs properly but What i want is to associate the button of
the menu to switch an image (actually to add rectangels offscreen and bring
it to the front).
The following codes runs properly. You just need to create a file
images.properties and put some images in a folder called images.

By the way this is related to metabolic pathways is there is any biologist
outside that like to help.

thanks

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.JMenu;
import javax.swing.JMenuItem;
import javax.swing.JCheckBoxMenuItem;
import javax.swing.JRadioButtonMenuItem;
import javax.swing.ButtonGroup;
import javax.swing.JMenuBar;
import java.util.*;

//PathwayViewer itself is not a visible component.
public class PathwayViewer extends JComponent implements ItemListener,
ListSelectionListener {
 private Vector imageNames; //Vector to call pictures
 private JLabel picture;
 private JList list; //List to call filenames
 private JSplitPane splitPane; //A Splitpane

 private String newline = "\n";

 //Double buffer (for flipping images)
 private Graphics offscreenGraphics; //A graphics object for the buffer
 private Image offscreenImage = null; //The off screen image for double
buffering
 private Dimension d = getSize();
 private int w = d.width;
 private int h = d.height;

 Thread main;

 Image imageBackground;

 //Menu definitions
 private JMenuBar menuBar;
 private JMenu Genes,About;
 private JMenuItem menuItem;
 private JRadioButtonMenuItem rbMenuItem;
 private JCheckBoxMenuItem cbMenuItem;

 public PathwayViewer() {
 ImageIcon imageBackground = createImageIcon("images/hsa00010.gif");

  // Initialise double buffering
/// repaint();

  //Read image names from a properties file.
  ResourceBundle imageResource;
  try {
   imageResource = ResourceBundle.getBundle("imagenames");
   String imageNamesString = imageResource.getString("images");
   imageNames = parseList(imageNamesString);
  } catch (MissingResourceException e) {
   handleMissingResource(e);
  }

  //
  //Create the list of images and put it in a scroll pane.
 //
  list = new JList(imageNames);
  list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
  list.setSelectedIndex(0);
  list.addListSelectionListener(this);
  JScrollPane listScrollPane = new JScrollPane(list);

 //
  //Set up the picture label and put it in a scroll pane.
 //
  ImageIcon firstImage = createImageIcon("images/" +
          (String)imageNames.firstElement());
  if (firstImage != null) {
   picture = new JLabel(firstImage);
  } else {
   picture = new JLabel((String)imageNames.firstElement());
  }
  JScrollPane pictureScrollPane = new JScrollPane(picture);

 //
  //Create a split pane with the two scroll panes in it.
 //
  splitPane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT,
           listScrollPane, pictureScrollPane);
  splitPane.setOneTouchExpandable(true);
  splitPane.setDividerLocation(150);

  //
  //Provide minimum sizes for the two components in the split pane.
 //
  Dimension minimumSize = new Dimension(100, 50);
  listScrollPane.setMinimumSize(minimumSize);
  pictureScrollPane.setMinimumSize(minimumSize);

  //
  //Provide a preferred size for the split pane.
  //
  splitPane.setPreferredSize(new Dimension(900, 600));
 }

 //Used by PathwayViewer2
 //public JList getImageList() {
 // return list;
 //}

 public JSplitPane getSplitPane() {
  return splitPane;
 }

 public void valueChanged(ListSelectionEvent e) {

  if (e.getValueIsAdjusting())
  return;

  //
  // Read file with image filenames
  //
  JList theList = (JList)e.getSource();
  if (theList.isSelectionEmpty()) {
   picture.setIcon(null);
   picture.setText(null);
  } else {
   int index = theList.getSelectedIndex();
   ImageIcon newImage = createImageIcon("images/" +
       (String)imageNames.elementAt(index));
   picture.setIcon(newImage);
   if (newImage != null) {
    picture.setText(null);

   } else {
    picture.setText("Image not found: "
        + (String)imageNames.elementAt(index));
   }
  }
 }

 //
 // Store image filenames in vector
 //
 protected static Vector parseList(String theStringList) {
  Vector v = new Vector(10);
  StringTokenizer tokenizer = new StringTokenizer(theStringList, " ");
  while (tokenizer.hasMoreTokens()) {
   String image = tokenizer.nextToken();
   v.addElement(image);
  }
  return v;
 }

 /*
 // Called when the image property file can't be found.
 */
 private void handleMissingResource(MissingResourceException e) {
  System.err.println();
  System.err.println("Can't find the properties file " +
         "that contains the image names.");
  System.err.println("Its name should be imagenames.properties, " +
         "and it should");
  System.err.println("contain a single line that specifies " +
         "one or more image");
  System.err.println("files to be found in a directory " +
         "named images. Example:");
  System.err.println();
  System.err.println(" images=Bird.gif Cat.gif Dog.gif");
  System.err.println();
  throw(e); //Used to be exit(1), but that causes the console to
       //go away under Java Web Start; this way, you're
       //more likely to see a relevant error message.
 }

 /*
  * Returns an ImageIcon, or null if the path was invalid.
  */
 protected static ImageIcon createImageIcon(String path) {
  java.net.URL imgURL = PathwayViewer.class.getResource(path);
 if (imgURL != null) {
  return new ImageIcon(imgURL);
  } else {
   System.err.println("Couldn't find file: " + path);
   return null;
  }
 }

 // Called to redraw image offscreen
 public void update(Graphics g){
 paint(g);
 }

 // Called to redraw image offscreen
 public void paint(Graphics g) {

  Rectangle box = g.getClipRect();
  //create the offscreenImage buffer
  if (offscreenImage == null)
  {
   System.out.println("Creating double buffering");
  // set up double buffer
  offscreenImage = createImage( w, h);
  offscreenGraphics = offscreenImage.getGraphics();
  }

  offscreenGraphics.drawImage(imageBackground,0,0,this);
  offscreenGraphics.setColor(getBackground());
  // clear the exposed area
  offscreenGraphics.setColor(getBackground());
  offscreenGraphics.fillRect(0, 0, box.width, box.height);
  offscreenGraphics.setColor(getForeground());
   // do normal redraw

 paint(offscreenGraphics);
  // Copy offscreen buffer to screen
 g.drawImage(offscreenImage ,10 ,10, this );

 //offscreenGraphics.setColor(getBackground());
 //offscreenGraphics.setColor(getForeground());

  }

 /**
  * Create the GUI and show it
  */
 private static void createAndShowGUI() {

 JMenuBar menuBar;
 JMenu Genes,About;
 JMenuItem menuItem;
  JRadioButtonMenuItem rbMenuItem;
 JCheckBoxMenuItem cbMenuItem;

  //Make sure we have nice window decorations.
  JFrame.setDefaultLookAndFeelDecorated(true);
  JDialog.setDefaultLookAndFeelDecorated(true);

 JFrame frame = new JFrame("PathwayViewer 1.0");

  //Implements Listener
 PathwayViewer listener = new PathwayViewer();

  //Create the menu bar
 menuBar = new JMenuBar();
 frame.setJMenuBar(menuBar);

  //Menu Genes
 Genes = new JMenu("Genes");
 Genes.setMnemonic(KeyEvent.VK_G);
 menuBar.add(Genes);

 //Menu About
 About = new JMenu("About");
 About.setMnemonic(KeyEvent.VK_A);
 menuBar.add(About);

  //Buttons in Genes
 ButtonGroup group = new ButtonGroup();

  //Button UP regulated
 rbMenuItem = new JRadioButtonMenuItem("Show UP regulated",new
ImageIcon("images/up.gif"));
 rbMenuItem.setSelected(false);
 rbMenuItem.setMnemonic(KeyEvent.VK_U);
 group.add(rbMenuItem);
 Genes.add(rbMenuItem);

 rbMenuItem.addItemListener(new ItemListener() {
  public void itemStateChanged(ItemEvent e) {
   if(e.getStateChange() == ItemEvent.SELECTED) {
   System.out.println("UP regulated");

   }
  }
  });

  //Button Down regulated
 rbMenuItem = new JRadioButtonMenuItem("Show DOWN regulated");
 rbMenuItem.setSelected(false);
 rbMenuItem.setMnemonic(KeyEvent.VK_D);
 group.add(rbMenuItem);
 rbMenuItem.addItemListener(listener);
 rbMenuItem.addItemListener(new ItemListener() {
  public void itemStateChanged(ItemEvent e) {
   if(e.getStateChange() == ItemEvent.SELECTED) {
   System.out.println("DOWN regulated");
   }
  }
  });Genes.add(rbMenuItem);

 //Button UP AND DOWN regulated
 rbMenuItem = new JRadioButtonMenuItem("Show UP and DOWN regulated");
 rbMenuItem.setSelected(true);
 rbMenuItem.setMnemonic(KeyEvent.VK_A);
 group.add(rbMenuItem);
 rbMenuItem.addItemListener(listener);
 Genes.add(rbMenuItem);
 rbMenuItem.addItemListener(new ItemListener() {
  public void itemStateChanged(ItemEvent e) {
   if(e.getStateChange() == ItemEvent.SELECTED) {
   System.out.println("BOTH regulated");
   //Graphics g = getGraphics();
   //update(g);
   }
  }
  });

 //Display the window.
 frame.pack();
 frame.setVisible(true);

  //Create and set up the window.
 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  PathwayViewer pathway = new PathwayViewer();
  frame.getContentPane().add(pathway.getSplitPane());

  //Display the window.
  frame.pack();
  frame.setVisible(true);
 }

 public void itemStateChanged(ItemEvent e) {} //override method

 // Returns just the class name -- no package info.
 protected String getClassName(Object o) {
  String classString = o.getClass().getName();
  int dotIndex = classString.lastIndexOf(".");
  return classString.substring(dotIndex+1);
 }

 public static void main(String[] args) {
  //Schedule a job for the event-dispatching thread:
  //creating and showing this application's GUI.
  PathwayViewer path = new PathwayViewer();
  javax.swing.SwingUtilities.invokeLater(new Runnable() {
  public void run() {

   createAndShowGUI();
   // //Image imageBackground;

  }
  });
 }
}