java.lang.IllegalStateException: Not on FX application thread Calling Function - multithreading

Question

Something strange is happening.. Untill 10 minutes ago I had no problem with this code. But now I have a problem updating JUST my VBOX from an external thread.
These are my three classes:
Controller Class:
public class Controller implements Initializable{
#FXML
private VBox slaveVbox;
private ButtonBar newNode = new ButtonBar();
private Circle c= new Circle();
private Button b= new Button();
private Label lname = new Label();
private Label lIMEI = new Label();
private Label lroot = new Label();
#Override
public void initialize(URL location, ResourceBundle resources) {
}
public void create(String imei, String permission,boolean isOnline) throws IOException{
if(!alreadyExist(imei)){
newNode = new ButtonBar();
b = setButtonSpec(imei + "btnHavefun");
c = setCircleSpec(imei + "statuOnline", isOnline);
lname= setLNameSpec(imei + "name");
lIMEI = setLIMEISpec(imei + "Imei");
lroot = setLrootSpec(imei + "root", permission);
newNode.getButtons().addAll(lname,lIMEI,lroot,b,c);
slaveVbox.getChildren().addAll(newNode);
}
}
}
Main Class:
public class MainApp extends Application {
FXMLLoader loader2;
private Stage primaryStage;
private BorderPane rootLayout;
#Override
public void start(Stage primaryStage) throws IOException {
this.primaryStage = primaryStage;
this.primaryStage.setTitle("Thypheon Application");
initRootLayout();
Controller controller2 = initDesign();
Connection con = new Connection(controller2);
Thread t = new Thread(con);
t.start();
primaryStage.setOnCloseRequest(new EventHandler<WindowEvent>() {
#Override
public void handle(WindowEvent e) {
Platform.exit();
System.exit(0);
}
});
}
public static void main(String[] args) {
launch(args);
}
public void initRootLayout(){
try {
FXMLLoader loader = new FXMLLoader(getClass().getResource("RootLayout.fxml"));
rootLayout = (BorderPane) loader.load();
Scene scene = new Scene(rootLayout);
primaryStage.setScene(scene);
primaryStage.show();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public Controller initDesign(){
try {
FXMLLoader loader2= new FXMLLoader(getClass().getResource("Design.fxml"));
AnchorPane anchor = (AnchorPane) loader2.load();
rootLayout.setCenter(anchor);
Controller controller = loader2.getController();
return controller;
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return null;
}
}
public Stage getPrimaryStage(){
return primaryStage;
}
}
Connection THREAD:
public class Connection implements Runnable {
String result;
Controller controller;
public Connection(Controller controller) {
this.controller = controller;
}
#Override
public void run() {
try {
controller.create("jhgjhgjh", "dssf", true);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
Debugging the Application Everything works perfectly untill I reach slaveVbox.getChildren().addAll(newNode); Here comes the exception..
After some attempt to solve the problem I figured out that if I create a ButtonBar and I insert it in the slaveVbox from Main (inside start()) it works fine.. So I ve tied to add controller2.create("FIRST", "FIRST", true); in my start() function like this:
#Override
public void start(Stage primaryStage) throws IOException {
this.primaryStage = primaryStage;
this.primaryStage.setTitle("Thypheon Application");
initRootLayout();
Controller controller2 = initDesign();
controller2.create("FIRST", "FIRST", true);
Connection con = new Connection(controller2);
Thread t = new Thread(con);
t.start();
primaryStage.setOnCloseRequest(new EventHandler<WindowEvent>() {
#Override
public void handle(WindowEvent e) {
Platform.exit();
System.exit(0);
}
});
}
But obviously my application shows two ButtonBars... One created in the start() function and one created inside the Connection Thread.. How Can I avoid this?? Why I can't directly add item inside my VBox directly from my Connecton thread??

Answer 1

You cannot update the UI from a thread other than the FX Application Thread. See, for example, the "Threading" section in the Application documentation.
It's not at all clear why you are using a background thread at all here: there doesn't seem to be any long-running code in the method you are calling. In general, if you have long-running code to call, you can call it in a background thread and then update the UI by wrapping UI update in a Platform.runLater(...).
public class Connection implements Runnable {
String result;
Controller controller;
public Connection(Controller controller) {
this.controller = controller;
}
#Override
public void run() {
try {
// execute long-running code here...
// perform any updates to the UI on the FX Application Thread:
Platform.runLater(() -> {
// code that updates UI
});
// more long-running code can go here...
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}