javafx thread synchronization while true

Question

I'm new to JavaFX and have some trouble with threads. My application has to do something like this (hard pseudocode):

start(){
  startLoop(); //new thread
  displayThingsSavedToSharedVariable();
}



loop(){
  while (true){
    doThings();
    saveThingsToSharedVariable();
  }
}

I want to display output from loop() in JavaFX GUI up to date, one per line in the terminal, but I don't know how to synchronize a thread with loop() with JavaFX thread. The shared variable is only an - not working - example of what I want to achieve, the main question is how to dynamically print text to JavaFX GUI from an infinite loop in another thread.

You don't need to poll data like that, consider using Observable. — m0skit0, May 23 '18 at 08:54
you can use the word volatile for store the variables in the main memory rather thread local stack — Hasnain Ali Bohra, May 23 '18 at 08:55

score 2 · Accepted Answer · answered May 23 '18 at 08:51

2

The correct way to update the javafx gui is to use Platform.runLater.

String mytext = deriveText();
Platform.runLater(()->{
    label.setText(mytext);
});

You could also consider using the Observable interface.

answered May 23 '18 at 08:51

matt

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you are Right @matt – Ng Sharma May 23 '18 at 08:53
I tried runLater(), but its code is executed only after I restart the GUI, for example 1. 1st run the program, infinite loop starts 2. runLater is never executed 3. I close the GUI, infinite loop keeps goins 4. I start the GUI and runLater() is finnally executed public void startServer(int capacity) { new Thread(() -> { Server server = new Server(capacity); server.start(); //here begins infinite loop Platform.runLater(() -> System.out.println("xD")); }).start(); } do I have to refresh GUI somehow? – 1337_ May 23 '18 at 08:59
@1337_ Can you include this more complete example in your original question? You need a javafx gui started to use Platform.runLater. It posts the runnable to an eventloop, and is eventually run on the application thread. Meanwhile your original thread is free to continue running. – matt May 23 '18 at 09:23
Observable interface was tht thing i was looking for, thanks. – 1337_ May 23 '18 at 09:49
ok, here comes another question. How can i chceck if ObservableList value changed in another thread and, depending on it infinitly display new value in GUI? (its going to be something like terminal log) – 1337_ May 23 '18 at 10:44
@1337_ you can add a listener. For example, you can have an ObservableValue and then add an changeListener. Note that the change listener will be called from the Platform thread. If you want a different thread to react. I would have your ChangeListener post a runnable to the thread you want it to run on. – matt May 23 '18 at 11:59

javafx thread synchronization while true

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