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Matheas Manssen · Guest

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?

Best regards,

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();
}
}
}

Rhino · Guest

"Matheas Manssen" <geheim> wrote in message
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Matheas Manssen · Guest

Hi Rhine,

Thank you for your reply.

I understand it's too much asked for you to put the program in your IDE.
However, I don't know how to generate a stack trace.
By the way, the bug is not in my program, but in the flushGraphics() method.

Best regards,

Matheas

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Paul Hamaker · Guest

Runs fine on my J2ME Wireless Toolkit, Java 1.5.0_06, WinXP Home. Let
it run for a while, no errors or quirks.
--------------------
Paul Hamaker, SEMM, teaching ICT since 1987
http://javalessons.com

Rhino · Guest

"Matheas Manssen" <geheim> wrote in message
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Darryl L. Pierce · Guest

Matheas Manssen wrote:

Matheas Manssen · Guest

Hi Rhino,

Darryl L. Pierce · Guest

Matheas Manssen wrote:

Matheas Manssen · Guest

Hi,

The screen is no longer updated. I used debug statements(System.out.println)
to determine were the problem is. It happens to be in the flushGraphics
method. The added EXIT command still works.

Best regards,

Matheas

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Matheas Manssen · Guest

Hi Darryl,

It's the Graphics object of a GameCanvas. You can use it during the life of
a the GameCanvas. So, it differs from the Graphics object which you get
passed in the paint() method.

Cheers,
Matheas Manssen

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