JavaFX working with threads and GUI

Question

I have a problem while working with JavaFX and Threads. Basically I have two options: working with Tasks or Platform.runLater. As I understand Platform.runLater should be used for simple/short tasks, and Task for the longer ones. However, I cannot use any of them.

When I call Thread, it has to pop up a captcha dialog in a middle of task. While using Task, it ignores my request to show new dialog... It does not let me to create a new stage.

On the other hand, when I use Platform.runLater, it lets me show a dialog, however, the program's main window freezes until the pop up dialog is showed.

I need any kind of solution for this. If anyone knows how to deal with this or had some similar experience and found a solution I am looking forward to hearing from you!

Answer 1

As puce says, you have to use Task or Service for the things that you need to do in background. And Platform.runLater to do things in the JavaFX Application thread from the background thread.

You have to synchronize them, and one of the ways to do that is using the class CountDownLatch.

Here is an example:

Service<Void> service = new Service<Void>() {
        @Override
        protected Task<Void> createTask() {
            return new Task<Void>() {           
                @Override
                protected Void call() throws Exception {
                    //Background work                       
                    final CountDownLatch latch = new CountDownLatch(1);
                    Platform.runLater(new Runnable() {                          
                        @Override
                        public void run() {
                            try{
                                //FX Stuff done here
                            }finally{
                                latch.countDown();
                            }
                        }
                    });
                    latch.await();                      
                    //Keep with the background work
                    return null;
                }
            };
        }
    };
    service.start();

Answer 2

Use a Worker (Task, Service) from the JavaFX Application thread if you want to do something in the background.

http://docs.oracle.com/javafx/2/api/javafx/concurrent/package-summary.html

Use Platform.runLater from a background thread if you want to do something on the JavaFX Application thread.

http://docs.oracle.com/javafx/2/api/javafx/application/Platform.html#runLater%28java.lang.Runnable%29