java - Using ProgressMonitorDialog in Eclipse 4 properly

Question

I have a set of APIs that do file operations e.g. saveToFile(CustomObject objectToSave);

Since a file operation could be lengthy I decided that some indication should be shown to the user e.g. progress bar.

I read about a ProgressMonitorDialog and so I tried it, but it doesn't exactly work as I need (or better I don't know how to use it properly).

Currently I do:

ProgressMonitorDialog progressDialog = new ProgressMonitorDialog(theShell);  
    try {  
        progressDialog.run(false, true, new IRunnableWithProgress() {  

        @Override  
        public void run(IProgressMonitor monitor) throws InvocationTargetException, InterruptedException {  
            monitor.beginTask("Saving your data", 100);  
            try {  
                Utils.saveToFile(objectToSave);  
            } catch (Exception e) {  
            // TODO Auto-generated catch block  
                e.printStackTrace();  
            }  
            monitor.done();   
        }  
     });   

This code shows a progress dialog very fast and ends, but the problem is that on a slower PC this would stack until the Utils.saveToFile returned, while I have no idea how to indicate intermediate process until the save is completed.

I found a thread mentioning about IProgressMonitor.UNKNOWN but it does not say about what happens in monitor during the performRead(_fileName, monitor);

How would I solve this?

Answer 1

ProgressMonitorDialog is a tricky piece of code. I guess the part you are missing is IProgressMonitor#worked(int) which will "grow" the progress bar. Below is a code example that should clarify how to use it:

public class Progress {
    public static void main(String[] args)
    {
        // Create your new ProgressMonitorDialog with a IRunnableWithProgress
        try {
            // 10 is the workload, so in your case the number of files to copy
            IRunnableWithProgress op = new YourThread(10);
            new ProgressMonitorDialog(new Shell()).run(true, true, op);
         } catch (InvocationTargetException ex) {
             ex.printStackTrace();
         } catch (InterruptedException ex) {
             ex.printStackTrace();
         }
    }

    private static class YourThread implements IRunnableWithProgress
    {
        private int workload;

        public YourThread(int workload)
        {
            this.workload = workload;
        }

        @Override
        public void run(IProgressMonitor monitor) throws InvocationTargetException, InterruptedException
        {
            // Tell the user what you are doing
            monitor.beginTask("Copying files", workload);

            // Do your work
            for(int i = 0; i < workload; i++)
            {
                // Optionally add subtasks
                monitor.subTask("Copying file " + (i+1) + " of "+ workload + "...");

                Thread.sleep(2000);

                // Tell the monitor that you successfully finished one item of "workload"-many
                monitor.worked(1);

                // Check if the user pressed "cancel"
                if(monitor.isCanceled())
                {
                    monitor.done();
                    return;
                }
            }

            // You are done
            monitor.done();
        }

    }
}

It will look something like this:

For your special case of using Utils.saveToFile you could hand the IProgressMonitor over to this method and call the worked() method from there.