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ExampleApplet.javaAPI DocExample3892Wed Apr 19 11:21:48 BST 2000actual

ExampleApplet.java

/*
 * @(#)ExampleApplet.java	1.2 97/01/14 Jeff Dinkins
 *
 * Copyright (c) 1995-1997 Sun Microsystems, Inc. All Rights Reserved.
 *
 */

package actual;

import java.applet.*;
import java.util.*;
import java.awt.*;

/**
 * This applet creates a window that has a pretty background 
 * picture, and adds several lightweight Gauge objects.
 *
 * Notice how parts of the lightweight Gauges are "transparent" 
 * and you can see the image behind them! Cool!
 */
public class ExampleApplet extends Applet {

  public void init() {
    
    setLayout(new BorderLayout());
    
    // create a double buffer panel and add it to the 
    // center of the frame
    DoubleBufferPanel dbp = new DoubleBufferPanel();
    dbp.setLayout(new BorderLayout());
    add("Center", dbp);
    
    // create a pretty panel and add it to the
    // double buffer panel
    
    //needed because ExampleApplet is running under Switcher
    Applet parentApplet;
    
    //Get the parent Applet object. 
    try {
      parentApplet = (Applet)getParent();
      PrettyPanel pp = new PrettyPanel(parentApplet);
      pp.setLayout(new FlowLayout());
      dbp.add("Center", pp);
      
      // *** Create Gauges
      Gauge gauge1  = new Gauge(Color.green.darker());
      pp.add(gauge1);
      
      Gauge gauge2  = new Gauge(Color.red.darker());
      pp.add(gauge2);
      
      Gauge gauge3 = new Gauge(Color.cyan);
      pp.add(gauge3);
      
      Gauge gauge4 = new Gauge();
      pp.add(gauge4);
      
      Gauge gauge5 = new Gauge(Color.blue.darker());
      pp.add(gauge5);
      
      Gauge gauge6 = new Gauge(Color.pink.darker());
      pp.add(gauge6);
      
      Gauge gauge7 = new Gauge(Color.yellow);
      pp.add(gauge7);
      
      // *** Create threads to drive the gauges
      GaugeThread gaugeThread1 = new GaugeThread(gauge1);
      gaugeThread1.start();
      
      GaugeThread gaugeThread2 = new GaugeThread(gauge2);
      gaugeThread2.start();
      
      GaugeThread gaugeThread3 = new GaugeThread(gauge3);
      gaugeThread3.start();
      
      GaugeThread gaugeThread4 = new GaugeThread(gauge4);
      gaugeThread4.start();
      
      GaugeThread gaugeThread5 = new GaugeThread(gauge5);
      gaugeThread5.start();
      
      GaugeThread gaugeThread6 = new GaugeThread(gauge6);
      gaugeThread6.start();
      
      GaugeThread gaugeThread7 = new GaugeThread(gauge7);
      gaugeThread7.start();
      
    } catch (ClassCastException e) {
      System.err.println("Parent isn't an Applet!");
      throw(e);
    }
  }
}


class PrettyPanel extends Container {
  Image background;

  PrettyPanel(Applet applet) {
      background = applet.getImage(applet.getCodeBase(),
				   "images/mandrill.jpg");
  }

  /**
   * override update to *not* erase the background before painting
   */
  public void update(Graphics g) {
      paint(g);
  }
 
  /**
   * paint the background picture, then call super.paint which
   * will paint all contained components 
   *
   * Note: You MUST call super.paint(g) or the lightweight
   * component(s) won't get painted.
   */
  public void paint(Graphics g) {
      g.drawImage(background, 0, 0, getSize().width, getSize().height,
                  getBackground(), this);
       super.paint(g); 
  }
}

class GaugeThread extends Thread {

  Gauge gauge;
  static int seed = 1;

  GaugeThread(Gauge gauge) {
      super("Gauge thread");
      this.gauge = gauge;
  }
 
  public void run () {
      Random rand = new Random(seed++);
      int i = gauge.getTotalAmount()/2;
      while(true) {
          float r = rand.nextFloat();
          if(r > .5) {
	      if(i < gauge.getTotalAmount())
                i+=2;
          } else {
	      if(i > 0)
		i-=2;
          }
	  
          gauge.setCurrentAmount(i);
          try {
              sleep(100);
          } catch (java.lang.InterruptedException e) {
          }
      }
  }
}