Concurrent background Task or Service with input and output arguments in JavaFX

Question

It would rather be a very simple concept, but since I am totally new to concurrency in JavaFX. I have been struggling to understand this concept.

While building a very simple JavaFX application, I wanted to perform some lengthy task in background and keep the UI safe from freezing.

In the example below, I am trying to create a simple background task service and then use ControlsFX Dialog to show progress bar over the main UI window.

However, I wanted to know how can I give some input arguments to this service and get a boolean output from it. This is really simple to do in C# BackgroundWorker, but still couldn't figure out in JavaFX. Any hints would be a great help.

Tried this simple example

    public void runTask(Stage stage) throws URISyntaxException, IOException {

    Service<Void> service = new Service<Void>() {

        @Override
        protected Task<Void> createTask() {
            return new Task<Void>() {
                @Override
                protected Void call() throws InterruptedException, URISyntaxException, IOException {
                    // some time consuming task here
                    // use the input arguments and perform some action on it
                    // then set the process result to a Boolean and return after the task is completed
                    // also keep hold back any other process to from executing on UI 
                    return null;
                }
            };
        }

    };

    Dialogs.create()
            .owner(stage)
            .title("Performing Task!")
            .masthead("Please wait...")
            .showWorkerProgress(service);

    service.setOnSucceeded(new EventHandler<WorkerStateEvent>() {

        @Override
        public void handle(WorkerStateEvent event) {
            System.out.println("done:" + event.getSource().getValue());
        }
    });

    service.setOnFailed(new EventHandler<WorkerStateEvent>() {

        @Override
        public void handle(WorkerStateEvent event) {
            throw new UnsupportedOperationException("Failed."); //To change body of generated methods, choose Tools | Templates.
        }
    });

    service.setOnCancelled(new EventHandler<WorkerStateEvent>() {

        @Override
        public void handle(WorkerStateEvent event) {
            throw new CancellationException("Cancelled."); //To change body of generated methods, choose Tools | Templates.
        }
    });

    service.start();

}

score 3 · Accepted Answer · answered Jan 20 '15 at 17:32

For input arguments, just define some parameters to the method. (You need them to be final in Java 7.)

To return a Boolean, just define the type of your Service and Task to be Boolean:

public void runTask(Stage stage, final int input /* can be any type */) throws URISyntaxException, IOException {

    Service<Boolean> service = new Service<Boolean>() {

        @Override
        protected Task<Boolean> createTask() {
            return new Task<Boolean>() {
                @Override
                protected Boolean call() throws InterruptedException, URISyntaxException, IOException {
                    // some time consuming task here
                    // use the input arguments and perform some action on it
                    // then set the process result to a Boolean and return after the task is completed
                    // also keep hold back any other process to from executing on UI 

                    Boolean returnValue = ... ;
                    return returnValue;
                }
            };
        }

    };

    Dialogs.create()
            .owner(stage)
            .title("Performing Task!")
            .masthead("Please wait...")
            .showWorkerProgress(service);

    service.setOnSucceeded(new EventHandler<WorkerStateEvent>() {

        @Override
        public void handle(WorkerStateEvent event) {
            System.out.println("done:" + event.getSource().getValue());
        }
    });

    service.setOnFailed(new EventHandler<WorkerStateEvent>() {

        @Override
        public void handle(WorkerStateEvent event) {
            throw new UnsupportedOperationException("Failed."); //To change body of generated methods, choose Tools | Templates.
        }
    });

    service.setOnCancelled(new EventHandler<WorkerStateEvent>() {

        @Override
        public void handle(WorkerStateEvent event) {
            throw new CancellationException("Cancelled."); //To change body of generated methods, choose Tools | Templates.
        }
    });

    service.start();

}

This creates Service instance each time you call runTask(...). Use Task itself and remove the Service. — ed22, Aug 28 '17 at 09:05

Concurrent background Task or Service with input and output arguments in JavaFX

1 Answers1