Novermber 3rd, 2014

More on Event Listeners:

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import javax.swing.JComponent;

/**
   This component displays a rectangle that can be moved. 
*/
public class RectangleMovingComponent extends JComponent
{  
   private static final int BOX_X = 100;
   private static final int BOX_Y = 100;
   private static final int BOX_WIDTH = 20;
   private static final int BOX_HEIGHT = 30;

   private Rectangle box;

   public RectangleMovingComponent()
   {  
      // The rectangle that the paintComponent method draws 
      box = new Rectangle(BOX_X, BOX_Y, BOX_WIDTH, BOX_HEIGHT);         
   }

   public void paintComponent(Graphics g)
   {  
      Graphics2D g2 = (Graphics2D) g;

      g2.draw(box);
   }

   /**
      Moves the rectangle by a given amount. 
      @param x the amount to move in the x-direction 
      @param y the amount to move in the y-direction 
   */
   public void moveBy(int dx, int dy)
   {
      box.translate(dx, dy);
      repaint();      
   }
}

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.Timer;

/** 	 	 	 	 	 	
   This program moves the rectangle.
*/
public class RectangleMover
{
   private static final int FRAME_WIDTH = 300;
   private static final int FRAME_HEIGHT = 400;

   public static void main(String[] args)
   {
      JFrame frame = new JFrame();

      frame.setSize(FRAME_WIDTH, FRAME_HEIGHT);
      frame.setTitle("An animated rectangle");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

      final RectangleMovingComponent component = new RectangleMovingComponent();
      frame.add(component);

      frame.setVisible(true);
      
      class TimerListener implements ActionListener
      {
         public void actionPerformed(ActionEvent event)
         {
            component.moveBy(1, 1);
         }
      }

      ActionListener listener = new TimerListener();

      final int DELAY = 100; // Milliseconds between timer ticks
      Timer t = new Timer(DELAY, listener);
      t.start();      
   }
}

Classwork/Homework:
Use the programs given to write a program, YI_BouncingBlock.java to make the block bounce when it reaches a all.