JavaFX Multithreading

Question

I am facing one problem in my JavaFx application.

Preface: I don't want to be specific to my application only but want to be generalized so that people like me will get an idea on similar situation.

Background: Implementing a Javafx application using fxml file and multi-threading concept.

Summary: I tried make an application which basically uses multi threading to do some task, and once multi- threading is completed, it will sequentially move to another task. While doing the multi-threading the Main GUI freezes.

What I did,

//This is Main class

Parent Root  -> defined on top
public Parent createContent(){
 try{
  root =  FXMLLoader.load(getClass().getResource("Layout.fxml"));
  }catch { .....}
 }

 public void start(){
    stage.setScene(new Scene(createContent()));
    Task<Void> task = new Task<Void>() {
            @Override
            public Void call() throws Exception {
                Thread.sleep(1000);
                return null ;
            }
        };
      task.setOnSucceeded(event->{
            stage.show();
        });
        new Thread(task).run();
  }
  public static void main(String[] args) {
        launch(args);
    }
// This is inside the controller on button click event
@FXML
private void start(ActionEvent event) { <---- This one is button click event
   Thread t1 = new Thread(new Mul());
    t1.start();
    Thread t2 = new Thread (new Mul());
    t2.start();
}

 // Finally 
public class Mul implements Runnable {
  public void type() {
    for (int a = 0; a < 200000; a++) {
        System.out.println( Thread.currentThread().getName()+ " says " + a);
    }
   }
    @Override
   public void run() {
     type();
   }

}

Now, here is the outcome. If I just start the threads from the controller then My main application does not freezes while the thread are running in background. However, since the application runs in a sequence, i.e the next step only works when the threads complete their work

I can use t1.join() and t2.join() , but doing so will freezes my main application(Main application here is the main GUI) and I cannot proceed with it until the threads are completed.

What could be the optimal solution, so that I can use multi threading without blocking the main application or What am I doing wrong here? (info, I came to this solution by following up different suggestions from Stack overflow and google)

basically follow the API that every frameworks gives you for concurrent environment and also you have to design that chain in order Not to stretch the resources for non- significant reasons. For java fx there are at least 2 basic types of threads , the first type is for doing background jobs and the second to draw at the UI without affecting the rest of the application. So i would suggest using an executor(with any implementation you like) and distinguish your tasks in order to do a stable app , also if you check your CPU usage at the time you call the 2 threads , i bet it will be 100% — AntJavaDev, Jun 26 '15 at 12:34

score 3 · Accepted Answer · answered Jun 26 '15 at 12:10

Why not do

Task<Void> task = new Task<Void>() {
    @Override
    public Void call() {
        Mul m1 = new Mul();
        m1.run();
        Mul m2 = new Mul();
        m2.run();
        return null ;
    }
};
new Thread(task).start();

If you really want to "chain" different tasks, call one from the other's onSucceeded handler:

Task<Void> task1 = new Task<Void>() {
    @Override
    public Void call() {
        new Mul().run();
        return null ;
    }
};

Task <Void> task2 = new Task<Void>() {
    @Override
    public Void call() {
        new Mul().run();
        return null ;
    }
};

task1.setOnSucceeded(e -> new Thread(task2).start());

new Thread(task1).start();

Obviously this is cleaner if you make Mul a Task subclass instead of a Runnable, and it's better to use an Executor with daemon threads, etc, but this should give you the idea.

JavaFX Multithreading

1 Answers1