Thread: Jar Embedded in Website: Double Buffering Issue?

I'm not sure if this would be the correct post, but I've started some simple development for my portfolio website. I embedded several different jars (as tests) with an Object tag and they all uploaded correctly. However, only 1 out of the many programs repainted correctly.

The problem:

The program flashes a lot. It will take the current background and display it (usually white/black) on top of the Images/Drawn shapes. However, if the program is receiving constant Mouse input, the program will display everything correctly.

Would this be a double buffering issue? None of my programs have been double buffered, and this is because they never required it. I use a Mac, and a good friend of mine can run my programs and view them perfectly.. But for others, who use Windows (probably a coincidence), have the same issue as I am having with the website.

I can post further information if necessary, and any help/advice would be great. I understand the basic concept of Double Buffering as well, but would like to know a bit more if possible as well. Thanks!

I embedded several different jars (as tests) with an Object tag and they all uploaded correctly

I am confused by this statement. Do you mean they are applets?

The program flashes a lot

Typically has to do with incorrect java2D painting, and nothing to do with double buffering. Construct an SSCCE to demonstrate.

Originally Posted by copeg

I am confused by this statement. Do you mean they are applets?

Sorry about that. They're .jar files. It's easier/faster to upload the several classes using a Jar instead of an Applet.

Here is the HTML snippet.

HTML Code:

      <!--[if !IE]>-->
      <object class="feature-item" classid="java:Main.class" 
              type="application/x-java-applet"
              archive="projects/Minesweeper.jar" 
              height="425" width="500" >
        <!-- Backup param -->
        <param name="archive" value="projects/Minesweeper.jar" />
      <!--<![endif]-->
        <object class="feature-item" classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93" 
                height="425" width="500" > 
          <param name="code" value="Main" />
          <param name="archive" value="projects/Minesweeper.jar" />
        </object> 

Here is the dummy code that represents what I'm doing. If you'd like to see the actual page, I can send over the URL.

import java.applet.Applet;
import java.awt.Color;
import java.awt.Graphics;
 
import javax.swing.JFrame;
 
@SuppressWarnings("serial")
public class Main extends Applet implements Runnable {
 
	public static int FPS = 10;
	public static int WIDTH = 500;
	public static int HEIGHT = 500;
	public static Minesweeper game;
 
	public Main(){
		init();
		game = new Minesweeper();
	}
 
	public void init() {
		setSize(WIDTH, HEIGHT);
		setBackground(Color.gray);
	}
 
	public void run() {
		while (true) {
			repaint();
			try {
				Thread.sleep(1000 / FPS);
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
	}
 
	public void stop() {
	}
 
	public void start() {
		new Thread(this).start();
	}
 
	public void paint(Graphics g) {
		game.draw(g);
	}
 
	public static void main(String args[]){
		JFrame frame = new JFrame();
		Applet app = new Main();
		frame.add(app);
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setSize(Main.WIDTH, Main.HEIGHT);
		frame.setTitle("SSCCE");
		frame.setResizable(false);
		frame.setVisible(false);
                app.init();
                app.start();
	}
 
}

What constitutes incorrect Java 2D Painting? My program draws perfectly fine on my computer. It just doesn't look great when distributing to others/my website.

The posted code is not an SSCCE that reproduces the problem (I have no clue what is in the Minesweeper class), so one can only guess. Perhaps someone else has better eyes than I because I don't see much aside from small things like calling super.paint() or that the game.draw method takes too long

What constitutes incorrect Java 2D Painting?

Things like painting to a graphics object of a Swing component that was retrieved from calling getGraphics(), not understanding the EDT and calling Thread.sleep from within the EDT, and many more things that could be more context dependent...I don't see anything glaring in this code (repaint() is thread safe)

Originally Posted by copeg

The posted code is not an SSCCE that reproduces the problem (I have no clue what is in the Minesweeper class)

Like I've stated, there is nothing fundamentally incorrect with the way I have been drawing anything. If I run the program on my computer, it looks fine. Also considering that one of my other friend's could run it as well without problems, gives me a bit of support.

I'm trying to figure out what confounding problem is, causing the program to display the way it is. My friend also programs frequently, so maybe it has something to do with older Java versions? I'm not sure.

I only know this:

- My program does work without error
- My program doesn't display well on websites/some computers
- I am not double buffering
- The program remains black/white screened until mouse movement
therefore...
- When constantly moving the mouse over the Program (in the website), it displays perfectly fine

I'm not trying to sound rude, and sorry if I am. I just don't believe anything is necessarily wrong with my code. I just want to understand what I need to do to make the program display well for others. I don't want to create something that only displays well for myself.

Edit: I have a feeling that it has something to do with obtaining focus, or something of the sort. I'm not too knowledgeable on this, but if the program won't update the screen until it receives input (in websites/other computers), maybe that's where we should start from.

Here is what I recommend trying: change all your AWT classes to Swing classes - an Applet becomes a JApplet, a Panel a JPanel. Swing is by default double buffered. In doing so, override paintComponent, not paint. And always call super.paintComponent to invoke the parent class paintComponent method.

It seems like that didn't work for me, I had the same reuslt. Do you have any other suggestions perchance?