java - Constant label updation from different class in javafx-fxml -

i unable change text of label other class. need update date , time on main screen, while may able perform other functions too, simultaneously. have used timesetting class, extends thread , in it's run() method, i've called updation command in infinite loop, using settext() , slept method second. on running this, nothing happens , on closing output window, error saying nullpointerexcpetion

here's code 2 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(); }  } 

launch() not complete until application exits. should start thread in start method of application.

furthermore new fxmldocumentcontroller() creates new instance of controller class - 1 isn't connected fxml, none of fields injected. can find examples of "communicating fxml" in stackoverflow docs, e.g. passing data fxml - accessing existing controller

also if work, you're still using thread different javafx application thread modify ui. should not done. instead use platform.runlater update 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) {     } }