[FIXED] Increase progress of ProgressBar in JavaFX via multiple threads

Issue

I'm creating a JavaFX application which would send multiple files over network, and I want to have a progress bar for the number of bytes sent. I already have the total size of the files which are about to be sent, however, I don't know how to increase the progress bar.

The problem is, I am sending the files concurrently, so I can't just set progress in my download class, as that would get overwritten by another threat.

This is what my download class look like:

        iStream = socket.getInputStream();
        bufferSize = socket.getReceiveBufferSize();
        fos = new FileOutputStream(file);
        bos = new BufferedOutputStream(fos);
        byte[] bytes = new byte[bufferSize];
        int count;
        while ((count = is.read(bytes)) >= 0) {
            bos.write(bytes, 0, count);
        }
        bos.close();
        is.close();

And I'm executing the class the following way:

List<Callable<String>> downloadTasks = new ArrayList<>();
Callable<String> download = new Download(new File(path), portnumber);
downloadTasks.add(download);
es.invokeAll(downloadTasks);

I have the total number of bytes in variable long totalSize in both classes.

Can you please help me on how I would achieve the bytes progress bar? Thanks

Solution

You can only update the progress bar from a single thread: the FX Application Thread. So the threading issue is moot; you can just increment a property representing the total number of bytes downloaded, and arrange to only update it from that thread.

So something like:

public class UploadProgressMonitor {

    private final long totalBytes ;
    private long downloadedBytes ;
    private final ReadOnlyDoubleWrapper progress = new ReadOnlyDoubleWrapper() ;

    public UploadProgressMonitor(long totalBytes) {
         this.totalBytes = totalBytes ;
    }

    private void doIncrement(long bytes) {
        downloadedBytes += bytes ;
        progress.set(1.0 * downloadedBytes / totalBytes);
    }

    public void increment(long bytes) {
        if (Platform.isFxApplicationThread()) {
            doIncrement(bytes);
        } else {
            Platform.runLater(() -> doIncrement(bytes));
        }
    }

    public ReadOnlyDoubleProperty progressProperty() {
        return progress.getReadOnlyProperty() ;
    }

    public final double getProgress() {
        return progressProperty().get();
    }
}

Now you can do things like:

long totalBytes = ... ;
UploadProgressMonitor monitor = new UploadProgressMonitor(totalBytes);
progressBar.progressProperty().bind(monitor.progressProperty());

and if you give each task a reference to the UploadProgressMonitor it just needs to do:

    int count;
    while ((count = is.read(bytes)) >= 0) {
        bos.write(bytes, 0, count);
        monitor.increment(count);
    }

Answered By - James_D