CODEWITHSUNDEEP
javamultithreadingconcurrency
user2517280
user2517280

Reputation: 221

New thread freezing application

I have an application which is quite resource intensive, it is using large images as input and some of the operations on these images can take a while. I am therefore looking to make some parts run in their own threads. To do this I have used the following code just to test out first:

Thread t1 = new Thread(new Runnable() {
public void run()
{
inputChooser.setFileFilter(filter);
    inputChooser.addChoosableFileFilter(filter);
    int img = inputChooser.showOpenDialog(this);

    if (img == JFileChooser.APPROVE_OPTION) {
        File file = inputChooser.getSelectedFile();
        String filename = file.getName();
        if (filename.contains("B10")) {
            greenBand = 1;
        }
        if (filename.contains("B20")) {
            greenBand = 2;
        }
        if (filename.contains("B30")) {
            greenBand = 3;
        }
        if (filename.contains("B40")) {
            greenBand = 4;
        }
        if (filename.contains("B50")) {
            greenBand = 5;
        }
        if (filename.contains("B60")) {
            greenBand = 6;
        }
        if (filename.contains("B70")) {
            greenBand = 7;
        }
        try {
            greenImage = ImageIO.read(file);
            ImageIO.write(greenImage, "JPEG", new File("img2_tmp.jpeg"));

            greenImage = ImageIO.read(new File("img2_tmp.jpeg"));
            if (greenImage.getWidth() > 8000 | greenImage.getHeight() > 7000) {
            greenImage = greenImage.getSubimage(1450, 1400, (greenImage.getWidth()-3200), (greenImage.getHeight()-3000));
            }
            update(greenImage, greenIcon, greenLabel);

            loadingBar.setIndeterminate(false);

            checkInput();
        } catch (IOException e) {
            JOptionPane.showMessageDialog(null, "Input Image Error", "Input Error", WARNING_MESSAGE);
        }

    }
}});
t1.start();

When I run the application it freezes when this code is called. However, I have managed to get it to work once, I am not sure how but it ran perfectly (not the first time, it froze a few times first and then randomly worked one time). I haven't changed any of the code just some of the indents and such to get it to fit with the rest of the code and ever since it just continues to freeze. A button action press calls this method where the above code is, as soon as the buttons pressed it freezes.

Is there a reason as to why this is happening?

Thanks in advance

Upvotes: 1

Views: 144

Answers (2)

Tanmay Patil
Tanmay Patil

Reputation: 7057

You are calling a non-thread-safe code (swing (is NOT thread safe)) from both threads (newly created and main thread) at the same time.

Make sure that you have decoupled the logic before creating new threads.

For this specific use case, I'd suggest that you use SwingWorkers in stead of threads, they are easy to use, and work well within the limitations of swing.

More about SwingWorkers at http://docs.oracle.com/javase/tutorial/uiswing/concurrency/worker.html

Hope this helps.
Good luck.

Upvotes: 3

corsiKa
corsiKa

Reputation: 82559

It's difficult to say exactly, but I notice that the variable greenImage and greenBand are not declared anywhere. That makes me think they are global variables. If something else has access to them, it's possible that they're causing some manipulation that sends your code into an infinite loop or does other unexpected Bad Things.

Upvotes: 1

Related Questions