Constant label updation from different class in javafx-fxml

Question

I am unable to change the text of my label from other class. I need to constantly update date and time on the main screen, while I may be able to perform other functions too, simultaneously. I have used a TimeSetting class, which extends Thread and in it's run() method, I've called the updation command in an infinite loop, using setText() and then slept the method for a second. But on running this, nothing happens and on closing the output window, I get an error saying NullPointerExcpetion

Here's the code for the two classes : FXMLDocumentController.java

package crt;

import java.io.IOException;
import java.net.URL;
import java.util.Date;
import java.util.ResourceBundle;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.fxml.Initializable;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Label; 
import javafx.stage.Modality;
import javafx.stage.Stage;
import javafx.stage.StageStyle;

public class FXMLDocumentController extends Thread implements Initializable     
{
@FXML
protected Label check;
@FXML
**protected Label date;**
@FXML
protected Label time;
@FXML
protected Label RRRR;
@FXML
protected Label DDDD;
@FXML
protected Label SSSS;
@FXML
protected Label temp;
@FXML
protected Label maxtemp;
@FXML
protected Label mintemp;

@FXML
private void handleButtonAction(ActionEvent event) throws IOException {
        //dc.setDate(date.textProperty().bind(valueproperty));

        FXMLLoader fxmlLoader = new FXMLLoader(getClass().getResource("menu.fxml"));
        Parent root1 = (Parent) fxmlLoader.load();
        Stage stage = new Stage();
        stage.initModality(Modality.APPLICATION_MODAL);
        stage.initStyle(StageStyle.UNDECORATED);
        stage.setTitle("MENU");
        stage.setScene(new Scene(root1));  
        stage.show();
 }
@Override
public void initialize(URL url, ResourceBundle rb)  {
}

FXMLDocument.fxml

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.ProgressBar?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.text.Text?>

<AnchorPane id="AnchorPane" prefHeight="367.0" prefWidth="510.0" xmlns="http://javafx.com/javafx/8.0.60" xmlns:fx="http://javafx.com/fxml/1" fx:controller="crt.FXMLDocumentController">
<children>
    <Button fx:id="button" layoutX="387.0" layoutY="302.0" minHeight="25.0" minWidth="80.0" onAction="#handleButtonAction" onTouchPressed="#handleButtonAction" text="Menu" />
    <Label fx:id="date" layoutX="56.0" layoutY="64.0" minHeight="25.0" minWidth="80.0" />
  <Label fx:id="time" layoutX="361.0" layoutY="64.0" minHeight="25.0" minWidth="80.0" text="S" />
  <Label fx:id="RRRR" layoutX="76.0" layoutY="100.0" minHeight="25.0" minWidth="70.0" />
  <Label fx:id="DDDD" layoutX="195.0" layoutY="100.0" minHeight="25.0" minWidth="70.0" />
  <Label fx:id="SSSS" layoutX="314.0" layoutY="100.0" minHeight="25.0" minWidth="70.0" />
  <Text layoutX="136.0" layoutY="163.0" strokeType="OUTSIDE" strokeWidth="0.0" text="TEMP :-" />
  <Label fx:id="temp" layoutX="275.0" layoutY="156.0" minHeight="25.0" minWidth="70.0" text="A" />
  <Text layoutX="136.0" layoutY="203.0" strokeType="OUTSIDE" strokeWidth="0.0" text="MAX TEMP :-" />
  <Label fx:id="maxtemp" layoutX="275.0" layoutY="188.0" minHeight="25.0" minWidth="70.0" text="B" />
  <Text layoutX="136.0" layoutY="243.0" strokeType="OUTSIDE" strokeWidth="0.0" text="MIN TEMP :-" />

  <Label fx:id="maxtemp" layoutX="275.0" layoutY="225.0" minHeight="25.0" minWidth="70.0" text="C" />
  <ProgressBar layoutX="401.0" layoutY="21.0" prefHeight="18.0" prefWidth="70.0" progress="0.0" />
  <Button fx:id="startbutton" layoutX="14.0" layoutY="18.0" mnemonicParsing="false" onAction="#startstart" text="START" />
  <Label fx:id="check" layoutX="42.0" layoutY="306.0" />

</children>
</AnchorPane>

TimeSetting.java

package crt;
import java.util.Date;
public class TimeSetting extends Thread {
@Override
public void run()
{
    FXMLDocumentController fdc = new FXMLDocumentController();
 //       fdc.load();
    int i=0;
    while(true)
    {
        Date d = new Date();
        fdc.date.setText("fd" + i);
        i++;
        try
        {
            Thread.sleep(1000);
        }
        catch(InterruptedException e)
        {
        }
    }
}
}

CRT.java

package crt;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class CRT extends Application {

@Override
public void start(Stage stage) throws Exception {
    Parent root = FXMLLoader.load(getClass().getResource("FXMLDocument.fxml"));

    Scene scene = new Scene(root);

    stage.setScene(scene);
    stage.show();
}


public static void main(String[] args) throws InterruptedException {
    launch(args);
    TimeSetting ts = new TimeSetting();
    ts.start();
}

}

Answer 1

launch() does not complete until the Application exits. You should start the thread in the start method of your application.

Furthermore new FXMLDocumentController() obviously creates a new instance of the controller class - one that isn't connected to any fxml, so none of the fields is injected. More info about communicating with a controller can be found here: Passing Parameters JavaFX FXML

Also if you get this to work, you're still using a thread different to the JavaFX application thread to modify the UI. This should not be done. Instead use Platform.runLater to update the UI:

while(true) {
    Date d = new Date();

    final String text = "fd" + i;
    Platform.runLater(() -> {
        fdc.date.setText(text);
    });

    i++;
    try {
        Thread.sleep(1000);
    } catch(InterruptedException e) {
    }
}