Loading images in Applet inherited class

[kourosh parsa]

Hi fellows.
I'm observing a very strange problem.
I have:
- a DrawingBoard class that implements JPanel
- an abstract Element class that implements a JPanel that is added to the DrawingBoard
- classes which implement the Element class for example Res class

Each element should have an image. When I load the image in the constructor of "Res", it does not get drawn until another element is added (next paint event).
I stepped through it; the paintComponent event does fire but the image size upon the first paint is -1 (but the image is NOT null).
Then I tried loading the images in the abstract Element class, and the problem does not occur except for the first time. so I still need to fix it because the first time also matters and also I prefer to load the image in the child class which has it's own properties such as size.
Does anyone have any idea why this is happening?

class DrawingBoard extends JPanel {
...
	@Override
	public void paintComponent(Graphics g) {
		super.paintComponent(g);
	}
}
//-------------------
public abstract class Element extends JPanel{
	protected Image image = null;

	public Element(){ // constructor
	}

	@Override
	public void paintComponent(Graphics g) {
		super.paintComponent(g);
		if (image!=null)
			g.drawImage(image, 0, 0, null);
	}
}
//-------------------
public class Res extends Element{
	public Res(){ // constructor
		super();
		Dimension mySize = new Dimension(50,25);
		invalidate();
		this.setSize(mySize);
		this.setBackground(Color.WHITE);

		try {
			URL imageURL = new URL(Constants.IMG_URL+"/res.gif");
			Image img = Toolkit.getDefaultToolkit().createImage(imageURL);
			Image scaled_img = img.getScaledInstance(mySize.width, mySize.height, Image.SCALE_SMOOTH);
			image = scaled_img;
			
		} catch (MalformedURLException e) {
			System.err.println("Resource not found.");
		}

		image = scaled_img;
	}
}

[kourosh parsa]

By changing the paint event to:

if (image!=null){
try {
while(image.getWidth(null)<1)
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
g.drawImage(image, 0, 0, null);
}

then it works indicating that there is a race condition problem. Of course that is not a fix, so I welcome any ideas.

[Maneesh Godbole]

kourosh parsa wrote:
...then it works indicating that there is a race condition problem. Of course that is not a fix, so I welcome any ideas.

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