How to put two different tasks in Threads

Question

I have following code. in this code i have an image which moves from left to right and a button which has an event. but i want to put these both tasks in Threads. so that it can work properly. the problem with this code is that button event does not work until it reaches to the right most point.

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

class MyImage extends JFrame implements ActionListener
{
   static int xPixel = 20;
   Image myImage, offScreenImage;
   Graphics offScreenGraphics;
   JPanel p = new JPanel();
   Button btn = new Button("bun");
   JFrame f = new JFrame();


   public MyImage()
   {
      myImage = Toolkit.getDefaultToolkit().getImage("mywineshoplogo.jpg");
      setExtendedState(JFrame.MAXIMIZED_BOTH);
      this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      setVisible(true);
      add(p);
      p.add(btn);
      moveImage();
      btn.addActionListener(this);
   }

   public void update(Graphics g)
   {
      paint(g);
   }

   public void paint(Graphics g)
   {
      int width = getWidth();
      int height = getHeight();
      if (offScreenImage == null)
      {
         offScreenImage = createImage(width, height);
         offScreenGraphics = offScreenImage.getGraphics();
      }
// clear the off screen image  
      offScreenGraphics.clearRect(0, 0, width + 1, height + 1);
// draw your image off screen  
      offScreenGraphics.drawImage(myImage, xPixel, 10, this);
// draw your image off screen  
// show the off screen image  
      g.drawImage(offScreenImage, 0, 0, this);
// show the off screen image  
   }

   void moveImage()   //left to right move
   {
  Thread hilo = new Thread() {

  public void run() {
 try {

      for (int i = 0; i < 530; i++)
      {

         xPixel += 1;
         repaint();
        // then sleep for a bit for your animation  
         try
         {
            Thread.sleep(4);
         } /* this will pause for 50 milliseconds */

         catch (InterruptedException e)
         {
            System.err.println("sleep exception");
         }
      }
  } //try
  catch (Exception ex) {
      // do something...
  }
  }
  };
  hilo.start();
   }

/*   void moveimg()   // right to left move
   {
      for (int i = 529; i > 0; i--)
      {
         if (i == 1)
         {
            moveImage();
         }
         xPixel -= 1;
         repaint();
// then sleep for a bit for your animation  
         try
         {
            Thread.sleep(40);
         } // this will pause for 50 milliseconds 

         catch (InterruptedException e)
         {
            System.err.println("sleep exception");
          }
      } 
   } */     

   public void actionPerformed(ActionEvent ae)
   {
      try
      {
         if (ae.getSource() == btn)
         {
            p.setBackground(Color.RED);
         }
      }
      catch (Exception e)
      {
         System.out.println("error");
      }
   }

   public static void main(String args[])
   {
      MyImage me = new MyImage();
   }
}

Answer 1

Whenever you are about to write Thread.sleep in your GUI code, stop yourself and introduce a task scheduled on Swing's Timer. This is exactly what you need with your code: schedule each update as a separate scheduled task on Timer. Timer is quite simple and straightforward to use, see for example this official Oracle tutorial.