Re: StarTrek class hangs

Hi,

When run the following class with midp 2.0, the midlet hangs. I think it
happens in the flushGraphics() method. Does anybody know the solution?

Matheas Manssen

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.lcdui.game.*;
import java.util.*;
import java.lang.*;

//Bestand: MyGameCanvas.java

class MyTimerTask extends TimerTask {
private MyGameCanvas canvas;

public void MyTimerTask( ) {
}

public void setCanvas ( MyGameCanvas myGameCanvas ) {
 canvas = myGameCanvas;
}

public void run() {
 canvas.update();
}
}

class MyGameCanvas extends GameCanvas {

private static int FOCUSAFSTAND = 50;
private static int STARS = 100;

private Graphics graphics;
private Random random;
int width, height;
int x, y;
int range;
int color;
int starField[][] = new int [STARS][3];

public MyGameCanvas( boolean surpressKeyEvents ) {
 super( surpressKeyEvents );

 graphics = getGraphics();
 random = new Random();
 width = getWidth();
 height = getHeight();
 range = Math.max( width, height );

 // vul starField
 for ( int star=0; star< STARS; star++ ) {
  int x, y, z;

  x = random.nextInt() % ( range/2 );
  y = random.nextInt() % ( range/2 );
  z = Math.abs(random.nextInt()) % ( range );

  starField[star][0] = x;
  starField[star][1] = y;
  starField[star][2] = z;
 }

 }

public void update() {
 color = 0x00000000;
 graphics.setColor( color );
 graphics.fillRect( 0, 0, width, height );

 color = 0x00FFFFFF;
 graphics.setColor( color );
 // Druk starField af
 for ( int star=0; star< STARS; star++ ) {
  int x, y, z;
  int px, py;

  x = starField[star][0];
  y = starField[star][1];
  z = starField[star][2];

  px = ( FOCUSAFSTAND * x ) / (FOCUSAFSTAND + z );
  py = ( FOCUSAFSTAND * y ) / (FOCUSAFSTAND + z );
  // Omrekenen naar coordiantenstelsel van scherm
  px = px + width/2;
  py = py + height/2;
  // Zet ster op scherm
  color = 0x00FFFFFF;
  graphics.setColor( color );

  graphics.drawLine( px, py, px, py );
  // Laat ster een stapje dichterbij komen
  starField[star][2] = ( z-1 );
  if ( starField[star][2] == 0 ) {
   starField[star][2] = range;

  }

 }

 flushGraphics();
}

}

public class StarTrek extends MIDlet implements CommandListener {

   private Command exitCommand;
   private TextBox textBox;
   private Display display;
   private MyGameCanvas gameCanvas;
   private MyTimerTask timerTask;
   private Timer timer;
   private boolean firstTime = true;

   public void startApp() {
if ( firstTime ) {
 firstTime = false;
        // Create the abstract command
 gameCanvas = new MyGameCanvas( true );
        exitCommand = new Command("Exit", Command.EXIT, 1);

        gameCanvas.addCommand(exitCommand);
        gameCanvas.setCommandListener(this);

        // Set the MIDlet's display to its initial screen
        display = Display.getDisplay(this);
        display.setCurrent(gameCanvas);

 timerTask = new MyTimerTask();
 timerTask.setCanvas( gameCanvas );
 timer = new Timer();
 timer.schedule( timerTask, 1000, 30);
}
   }

   public void pauseApp() {
   }

   public void destroyApp(boolean unconditional) {
   }

   public void commandAction(Command command, Displayable screen) {
       if (command == exitCommand) {
        destroyApp(false);
        notifyDestroyed();
       }
   }
}