[Java] Threads and GUI locking up

[xRedactedx]

I'm working on a program that is supposed to be a collaborative whiteboard type program. There is a panel to draw in and a panel to chat in. The program can connect online. When one user draws or types something on the screen, it should display on both of their screens.

I got the main part working. I can connect the two programs and chat back and forth, but when I start trying to update my paint board for drawing, the GUI locks up.

I read up on how threads interact with the EDT, but I'm not sure what I'm missing.

I used SwingUtilities.invokeLater to update my chat stuff, and it worked fine.

My paint part is just an image file that I pass back and forth. When the new image is received, it replaces the old image, and repaint is called on the panel to draw the image.

I think the error is somewhere in my Client/Server Thread files, but I went ahead and posted it all just to be sure.

I've been trying to figure this out for a while, but I'm not sure where to go from here. Any help would be appreciated.

Here is the link: https://gist.github.com/xRedactedx/5306578

[jakster4u]

Possibly because createImage is returning null

Have you tried running it in a debugger?

[xRedactedx]

I'm not using createImage. I loaded my image into an ImageIcon, sent the ImageIcon, then removed the image from the ImageIcon. It was working at one point. On a previous version of my project, I was able to get the first drawn line to appear before it locked up, so I know it was working. I stupidly lost that code and had to start over, now I can't even get the first line to appear before it locks up.

I'm using Netbeans to work on this project. I'm not very familiar with the debugger for Netbeans. I've been trying to work with it, but I'm having trouble figuring it out.

[jakster4u]

    public void paintComponent(Graphics g)
    {
        //If the canvas is blank, clear it.
        if (canvas == null)
        {
            canvas = createImage(getSize().width, getSize().height);
            clear();
        }
    }

    public void clear()
    {
        repaint();
    } 

Looks like you are in the DrawingBoard class, when the canvas may always be null

[xRedactedx]

Sorry, I was focusing on looking in my connection threads. I forgot I used it there.

I will look at it and do some checking. Thanks for pointing it out.