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// S.S. Java 2 - an animation demo adapted from Sun's Java Tutorial.
// This version uses a swing timer to send actionEvents at regular
// intervals.  The animation is performed by moving a swing JLabel
// (which remember can be a graphic) in a higher layer of a JLayerPane
// while the background image is shown in a lower layer.
// The space ship S.S. Java is moved across a star field, and the
// user can click the mouse to start/stop the animation.
//
// The animation uses a "frame number" to advance the image
// a certain number of pixels per repaint update (5).  This number
// is used modulo the width of the applet (which is the width of
// the background image).
//
// Notice how when used as an appet a MediaTracker is used to
// preload the image, and how the Applet start/stop methods are
// used in conjunction with the boolean "frozen" to control the
// animation.  Also a main has been included so this program can
// be run as a stand-alone as well.  Notice no media tracker is
// needed in this case, but certain window event handler methods
// are used to control the animation, just like the applet start
// and stop.
//
// Written 3/2001 by Wayne Pollock, Tampa Florida USA.

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

public class Ssjava2 extends JApplet implements ActionListener
{
    int frameNumber = -1;
    static final int pelsPerUpdate = 2;  // a "pel" is a pixel
    Timer timer;
    boolean frozen = false;

    JLayeredPane lp;
    JLabel bgLabel, fgLabel;
    int fgHeight, fgWidth;
    int bgHeight, bgWidth;
    static String fgFile = "rocketship.gif";  
    static String bgFile = "starfield.gif";

    // Invoked only when run as an applet:
    public void init()
    {   Image bgImage = getImage( getCodeBase(), bgFile );
        Image fgImage = getImage( getCodeBase(), fgFile );
        buildUI( getContentPane(), bgImage, fgImage );
    }

    // Do this when run as Applet or application:
    void buildUI ( Container container, Image bgImage, Image fgImage )
    {   final ImageIcon bgIcon = new ImageIcon( bgImage );
        final ImageIcon fgIcon = new ImageIcon( fgImage );
        bgWidth = bgIcon.getIconWidth();
        bgHeight = bgIcon.getIconHeight();
        fgWidth = fgIcon.getIconWidth();
        fgHeight = fgIcon.getIconHeight();
        
        //Set up a timer that calls this object's action handler
        timer = new Timer( 40, this ); //delay = 40 ms
        timer.setInitialDelay( 0 );
        timer.setCoalesce( true );

        //Create a label to display the background image.
        bgLabel = new JLabel( bgIcon );
        bgLabel.setOpaque( true );
        bgLabel.setBounds( 0, 0, bgWidth, bgHeight );

        //Create a label to display the foreground image.
        fgLabel = new JLabel( fgIcon );
        fgLabel.setBounds( -fgWidth, -fgHeight, fgWidth, fgHeight );

        // Create the layered pane to hold the labels:
        lp = new JLayeredPane();
        lp.setDoubleBuffered( true );
        lp.setPreferredSize( new Dimension( bgWidth, bgHeight ) );
        lp.addMouseListener( new MouseAdapter()
          {  public void mousePressed( MouseEvent e )
             {  if ( frozen )
                {   frozen = false;
                    startAnimation();
                } else
                {   frozen = true;
                    stopAnimation();
          }  }  }
        );

        lp.add( bgLabel, new Integer(0) );  // low layer
        lp.add( fgLabel, new Integer(1) );  // high layer
        container.add( lp, BorderLayout.CENTER );
    }
                
    // Invoked by the applet browser only:
    public void start ()
    {  startAnimation();  }

    // Invoked by the applet browser only:
    public void stop ()
    {  stopAnimation();  }

    public synchronized void startAnimation ()
    {  if ( ! frozen && ! timer.isRunning() )
          timer.start();
    }
            
    public synchronized void stopAnimation ()
    {  if ( timer.isRunning() )
          timer.stop();
    }

    public void actionPerformed ( ActionEvent e )
    {
       frameNumber++;   // Advance animation frame.
       int pos = ( ( frameNumber * pelsPerUpdate ) %
          ( fgWidth + bgWidth ) ) - fgWidth;
       fgLabel.setLocation( pos, ( bgHeight - fgHeight ) / 2 );
    }   

    // Invoked only when run as an application:
    public static void main( String [] args )
    {  Toolkit tk = Toolkit.getDefaultToolkit();
       Image bgImage = tk.getImage( bgFile );
       Image fgImage = tk.getImage( fgFile );
       final Ssjava2 me = new Ssjava2();
       JFrame f = new JFrame( "S. S. Java 2" );
       f.addWindowListener( new WindowAdapter()
         {  public void windowIconified ( WindowEvent e )
            {  me.stopAnimation();
            }
            public void windowDeiconified ( WindowEvent e )
            {  me.startAnimation();
            }
            public void windowClosing ( WindowEvent e )
            {  System.exit( 0 );
            }
         }
       );
       me.buildUI( f.getContentPane(), bgImage, fgImage );
       f.setSize( 500, 125 );
       f.setVisible( true );
       me.startAnimation();
    }
}