drawjpanel.java

来自「32个java程序源代码」· Java 代码 · 共 114 行

// Tutorial 20: DrawJPanel.java
// This class draws a random rectangle every .25 seconds.
import java.awt.*;
import java.awt.event.*;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.Random;
import javax.swing.*;

public class DrawJPanel extends JPanel
{
   // Random object to create random numbers
   private Random randomNumber = new Random();

   // Timer object to generate events
   private Timer drawTimer;

   // ArrayList object to hold MyRectangle objects
   private ArrayList rectangleArrayList = new ArrayList();

   // array of possible MyRectangle colors
   private Color[] colors = { Color.BLUE, Color.ORANGE, Color.PINK,
      Color.CYAN, Color.MAGENTA, Color.YELLOW, Color.BLACK,
      Color.WHITE, Color.RED, Color.GREEN };
      
   // no-argument constructor
   public DrawJPanel()
   {
      super();

      drawTimer = new Timer( 250, 

         new ActionListener() // anonymous inner class
         {
            // event handler called every 250 microseconds
            public void actionPerformed( ActionEvent event ) 
            {
               drawTimerActionPerformed();   
            }
            
         } // end anonymous inner class
         
      ); // end call to new Timer

      drawTimer.start(); // start timer

   }  // end contructor
         
   // create new MyRectangle object and add it to rectangleArrayList
   private void drawTimerActionPerformed()
   {
      // get random dimensions and a random color
      int x = randomNumber.nextInt( 380 );
      int y = randomNumber.nextInt( 380 );
      int width = randomNumber.nextInt( 150 );
      int height = randomNumber.nextInt( 150 );
      int color = randomNumber.nextInt( 10 );

      // create MyRectangle object and add it to rectangleArrayList
      MyRectangle rectangle = new MyRectangle( x, y, width, height,
         colors[ color ] );
      rectangleArrayList.add( rectangle );

      repaint();

   } // end method drawTimerActionPerformed

   // draw all rectangles
   public void paintComponent( Graphics g )
   {
      super.paintComponent( g );

      // create iterator
      Iterator rectangleIterator = rectangleArrayList.iterator();

      MyRectangle currentRectangle; // create MyRectangle

      // iterate through ArrayList and draw all MyRectangles
      while ( rectangleIterator.hasNext() )
      {
         currentRectangle = 
            ( MyRectangle ) rectangleIterator.next();

         currentRectangle.draw( g ); // draw rectangle
      } 

   } // end method paintComponent

   // clear rectangleArray
   public void clear()
   {
      rectangleArrayList.clear(); // clear ArrayList

      repaint(); // repaint JPanel

   } // end method clear
      
} // end class DrawJPanel

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