Custom Asynchronous Tasks in JavaFX

August 26th, 2009 by Martin Leave a reply »

As I mentioned in my previous blog, during my experiments with JavaFX I needed to run certain tasks on a separate thread (e.g. calls to a remote web service via Jersey Client API). One can do it in JavaFX using JavaTaskBase class, but I wanted something simpler, something similar to what FXexperience blog suggested. So, I created a custom subclass of javafx.async.Task named AsyncTask that allowed me to make asynchronous calls as follows:

    AsyncTask {
        run: function() {
            // add the code you want to run asynchronously

        onDone: function() {
            // this is executed once the "run" method finishes running

Here is the source code for the AsyncTask class together with the helper Java class it’s using. It should be self explanatory.

import javafx.async.Task;

public class AsyncTask extends Task, AsyncTaskHelper.Task {
    /** Function that should be run asynchronously.
    public var run: function() = null;

    // the helper
    def peer = new AsyncTaskHelper(this);

    // used to start the task
    override function start() {
        started = true;
        if (onStart != null) onStart();

    // don't need stop - isn't implemented
    override function stop() {
        // do nothing

    // called from the helper Java class from a different thread
    override function taskRun() {
        // run the code to be run asynchronously
        if (run != null) run();
        // send a notification (on the dispatch thread) the code finished running
        FX.deferAction(function() {
            done = true;
            if (onDone != null) onDone();
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class AsyncTaskHelper implements Runnable {
    // Using a fixed threadpool to run the asynchronous task
    private static final ExecutorService QUEUE = Executors.newFixedThreadPool(10);
    // the "parent" JavaFX AsyncTask instance
    private final Task peer;

    public AsyncTaskHelper(Task peer) {
        this.peer = peer;

    // called from AsyncTask.start() method - will add this task
    // to the thread pool queue
    public void start() {

    // called by the thread pool queue to start the task
    public void run() {

    // interface to be implemented by the "parent" JavaFX AsyncTask
    public static interface Task {
        public void taskRun();


  1. sidleal says:

    nice approach. thanks man!

Leave a Reply