Controlling JavaFX GUI from Other Methods?

Question

Basically, I'm creating a program that syncs HUE lights, and I'm having trouble incorporating the Listener that detects when the light bridge has been connected with my JavaFX GUI; I want it to switch a Label from "Not Connected" to "Connected" whenever the listener detects that it has connected.

Here's some pseudocode of how the program is structured.

public class MainClass extends Application {

boolean connected;
Label label;

public static void main(){
    launch(args);                       //Neccesary to start JavaFX
}

public static void start(){
    ConnectToHueLights();               //Takes abt 30s to connect to bridge
    Label label = “Searching for connection”;       //Message while connecting
    Window.addLabel();                  //Adds label to hue lights
    Window.show();                  //Makes window visible
}

private HueLightsListener(){
    //Once connected, can do whatever inside of a void method inside of this Listener
    private void onConnectionResponds(){
        label = “Connected”
        connected = true;
    }
}

public void ConnectToHueLights(){
    create new Listener();
}

Basically, the label doesn't change whenever the listener is active, and I'm not sure how to do that.

Thanks!

Yeah, I know, this is psuedo-code. I just want to know why JavaFX won't let me update labels from outside of the start() method and how to go about doing that. The actual code is complicated because of how big the GUI is and how the HUE lights work — Nick Mullen, Aug 26 '17 at 15:04
Did you add `System.out.println("Hello!);` in the `Listener` to make sure it's popping? — SedJ601, Aug 26 '17 at 15:13
No I know the listener is being called because I can do a System.out.println("Connected"); and you're right I think that it isn't updating because its not inside the start() method, but how would you suggest updating it or going about getting the listener to propagate to the start() method? — Nick Mullen, Aug 26 '17 at 15:30

score 1 · Answer 1 · answered Aug 27 '17 at 05:58

Use a suitable Worker to establish the connection to the bridge. Choose Task for a single unit of work; choose Service to manage multiple tasks. Use the task's updateMessage() method to notify the worker's message property listeners. You can pass a reference to the update method to your HueLightsListener, as shown here.

HueLightsListener listener = new HueLightsListener(this::updateMessage);

Your implementation of onConnectionResponds() can then tell the reference to accept() messages as needed.

public void onConnectionResponds() {
    updater.accept("Connected");
    …
}

As an aside, your implementation of call(), which runs in the background, can periodically poll the connection, while checking isCancelled(), and then send more commands once connected.

Controlling JavaFX GUI from Other Methods?

1 Answers1