Why does this code run slowly on some devices?

Question

Hi please look this code , when i run it on nokia N97 its run very slow but i test it on samsung corby its run true , i think if i use game canvas problem be sloved . what should i do to solve this problem .

public class MIDPCanvas extends GameCanvas implements Runnable {

Graphics g;
Image img;
int x = getWidth() / 2;
Thread t = new Thread(this);

public MIDPCanvas() {
    super(true);

    try {
        img = Image.createImage("/pic.jpg");
    } catch (IOException ex) {
        ex.printStackTrace();
    }

    g = getGraphics();
    g.setColor(150, 230, 200);
    g.fillRect(0, 0, getWidth(), getHeight());

    t.start();
}

public void run() {
    while (true) {
        g.drawImage(img, x, getHeight() / 2, Graphics.VCENTER | Graphics.HCENTER);
        x--;
        flushGraphics();
    }
   }
}

thanks

Answer 1

Since you have an infinite loop in run(), I would guess that one of the calls in the while loop blocks on the Corby, or that device is somehow throttling your process:

    while (true) {
        g.drawImage( ... );
        x--;
        flushGraphics();
    }

Answer 2

This is a very bad way of doing animation.

If you must use the infinite loop approach, at least include a yield() or Thread.sleep(100) on every iteration. But a much better approach is to use Display.callSerially(). This will ensure the device animates as fast as it can.

Google is your friend to explain all about how to use this method.

Personally, in many years of doing high-complexity J2ME apps with plenty of animation in, I have never used GameCanvas -- always Canvas, overriding the paint() method and animating using callSerially().

Answer 3

this is new code but there is no move

public class MIDPCanvas extends Canvas implements Runnable {

Graphics g;
Image img;
int x = getWidth() / 2;
Thread t = new Thread(this);
Display display;

public MIDPCanvas(Display display) {

    this.display = display;
    try {
        img = Image.createImage("/pic.jpg");
    } catch (IOException ex) {
        ex.printStackTrace();
    }

    t.start();
}

public void run() {
    while (true) {
        x--;
        repaint();
        display.callSerially(this);
    }
}

protected void paint(Graphics g) {
    g.drawImage(img, x, getHeight() / 2, Graphics.VCENTER | Graphics.HCENTER);
    display.callSerially(this);
}

}