import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.util.*;
import java.util.concurrent.*;
import javax.swing.*;

public class SwingWorkerTest
{
   public static void main(String[] args) throws Exception
   {
      EventQueue.invokeLater(new Runnable()
         {
            public void run()
            {
               JFrame frame = new SwingWorkerFrame();
               frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
               frame.setVisible(true);
            }
         });
   }
}

/**
 * This frame has a text area to show the contents of a text file, a menu to open a file and cancel
 * the opening process, and a status line to show the file loading progress.
 */
class SwingWorkerFrame extends JFrame
{
   public SwingWorkerFrame()
   {
      chooser = new JFileChooser();
      chooser.setCurrentDirectory(new File("."));

      textArea = new JTextArea();
      add(new JScrollPane(textArea));
      setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);

      statusLine = new JLabel(" ");
      add(statusLine, BorderLayout.SOUTH);

      JPanel panel = new JPanel();
      add(panel, BorderLayout.NORTH);
      
      openButton = new JButton("Open");
      panel.add(openButton);
      openButton.addActionListener(new ActionListener()
         {
            public void actionPerformed(ActionEvent event)
            {
               // show file chooser dialog
               int result = chooser.showOpenDialog(null);

               // if file selected, set it as icon of the label
               if (result == JFileChooser.APPROVE_OPTION)
               {
                  textArea.setText("");
                  openButton.setEnabled(false);
                  final File file = chooser.getSelectedFile();
                  Thread background = new Thread(new Runnable() 
                     {
                        public void run() 
                        {
                           try 
                           {
                              Scanner in = new Scanner(new FileInputStream(file));
                              final int[] lineNumber = new int[1];
                              while (in.hasNextLine())
                              {
                                 final String line = in.nextLine();
                                 lineNumber[0]++;
                                 EventQueue.invokeLater(new Runnable()
                                    {
                                       public void run()
                                       {
                                          statusLine.setText("" + lineNumber[0]);
                                          textArea.append(line);
                                          textArea.append("\n");
                                       }
                                    });
                              }
                           }
                           catch (IOException ex) 
                           {
                              ex.printStackTrace();
                           }
                           EventQueue.invokeLater(new Runnable()
                              {
                                 public void run()
                                 {
                                    openButton.setEnabled(true);
                                 }
                              });                           
                        }
                     });
                  
                  background.start();
               }
            }
         });

      exitButton = new JButton("Exit");
      panel.add(exitButton);
      exitButton.addActionListener(new ActionListener()
         {
            public void actionPerformed(ActionEvent event)
            {
               System.exit(0);
            }
         });
   }

   private JFileChooser chooser;
   private JTextArea textArea;
   private JLabel statusLine;
   private JButton openButton;
   private JButton exitButton;

   public static final int DEFAULT_WIDTH = 450;
   public static final int DEFAULT_HEIGHT = 350;
}