/* PingPongApplet: example of input from text field and button components
   in an applet which animates.
   -bds 10/98

  All println's are for debugging only.
*/
import java.applet.*;
import java.awt.*;
import java.awt.event.*;

// Applet handles user interface
// A second thread named PingPongBall handles animation (and sleeps a lot). 
// Use of this thread in the applet is denoted (at line end) by ////// 
public class PingPongApplet extends Applet implements ActionListener {
  // methods defined are init, paint, actionPerformed.
  
  private Dimension size;
  private PingPongBall animator = new PingPongBall( this );  //////
  private TextField distance_source = new TextField( 12 );
  private Button on_off = new Button( "on/off" );

  // set the relations among components, threads.
  public void init() {

    this.  add( distance_source );  // Put the TextField in this applet.
    // Tell it who handles the event that text is entered in the field.
    distance_source.addActionListener( this ); 
    distance_source.setText( "distance please" ); // just an initial val

    this.  add( on_off ); // put the Button in this applet
    // Tell it who handles mouse click events on the button.
    on_off. addActionListener( this );  

    setBackground( Color.white );
    running = true;
    animator.start(); //////
  } // method init 

  // Draw a ping pong table.
  public void paint( Graphics page ) {
    size = getSize(); // could have changed

    // Draw the table.
    page.setColor( Color.red );
    page.drawRect( size.width/10, size.height/10,
                   8*size.width/10, 8*size.height/10);
    page.drawLine(size.width/2, size.height/10, size.width/2, 9*size.height/10);

    System.out.println(" Paint: drew table");
  } // method paint

  private boolean running; // to know whether to suspend or resume action.

  // Handle the on_off or distance_source events.
  public void actionPerformed( ActionEvent event ) {
    System.out.println( event.toString() ); // just curious

    String cmd = event.getActionCommand();
    if ( cmd.equals( "on/off" ) ) { // Toggle the animation on or off.
      if ( running ) 
	animator.suspend(); //////
      else 
	animator.resume(); //////
      running = !running; // if we was, we aint; if we warnt, we is.
    }
    else { // Use textfield input to set the distance the ball moves.
      animator.setDistance( Integer.parseInt( cmd ) ); //////
    } 
  } // method actionPerformed

} // class PingPongApplet


////// continuation of file PingPongApplet.java //////////////////////////////
// PingPongBall draws itself in various positions on an associated applet.
class PingPongBall extends Thread {
  // methods defined are: run, paintBall, setDistance, setPositionData.

  private Point center = new Point(); // center of window
  private int diameter; // of the ping pong ball
  private int distance = 1; // of ball from center of table, unit is diameters.
  private PingPongApplet applet; // for whom I Animate
  private Graphics page; // And the applet's graphics for me to write on.

  PingPongBall() { 
    System.out.println("PingPongBall() constructor called ");
  }

  PingPongBall( PingPongApplet whoIAnimate ) {
    applet = whoIAnimate;
    System.out.println("PingPongBall(PingPongApplet) constructor called");
  }

  public void run() {
    System.out.println("PingPongBall.run() called");
    page = applet.getGraphics();
    page.setColor( Color.white ); 
    page.setXORMode( Color.green );
    int i = 1;
    Sys.snooze(100); // let applet get ready (..there is a better way)
    while (true) {
      setPositionData(applet.getSize()); // could change any second.
      //draw
      int j = i*distance;
      paintBall( j );
      Sys.snooze(1000); 
      paintBall( j );
      i = (i == 1)? -1 : 1; // alternates 1, -1, 1, -1, 1, ...
    }
  } // method run

  private void paintBall( int d ) {
    page.fillOval( center.x + d*diameter, center.y - diameter/2, 
                   diameter, diameter );
  }

  public void setDistance( int distance ) { this.distance = distance; }

  private void setPositionData(Dimension size) {
    diameter = (size.width + size.height)/30;
    center.x = (size.width-diameter)/2; 
    center.y = size.height/2; 
  } // method setPositionData


} // class PingPongBall

/*
<applet code="PingPongApplet.class" width=600 height=200>
</applet>
*/