Label in javafx does not change

Question

This is the code for controller

package Views;

import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.text.SimpleDateFormat;
import java.time.LocalDate;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.ResourceBundle;

import javax.imageio.ImageIO;

import javafx.embed.swing.SwingFXUtils;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.image.Image;

public class menuController {

    @FXML
    private Label eNameLabel;
    @FXML
    private Button productListButton;
    @FXML
    private Button employeeListButton;
    @FXML
    private Button ingredientListButton;
    @FXML
    private Button addProductButton;
    @FXML
    private Button addIngreidentButton;
    @FXML
    private Button addEmployeeButton;
    @FXML
    private Button LogOutButton;
    @FXML
    private Label clockLabel;



    public void initialize(URL arg0, ResourceBundle arg1) {
        clock();
    }

    public void clock(){
        Calendar cal = new GregorianCalendar();
    //  int day= cal.get(Calendar.DAY_OF_MONTH);
    //  int month = cal.get(Calendar.MONTH);
    //  int year = cal.get(Calendar.YEAR);

        Date currentDate = new Date();
        SimpleDateFormat dateFormat = new SimpleDateFormat("MM/dd/yyyy");

    //  int second = cal.get(Calendar.SECOND);
    //  int minute = cal.get(Calendar.MINUTE);
    //  int hour = cal.get(Calendar.HOUR);

        this.clockLabel.setText(dateFormat.format(currentDate));
    }
}

My label is not changed when I start my program. I have checked that the label id is given in the scene-builder and everything is connected to its controller or variable.

This is the fxml file that is connected to the controller.

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

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.layout.HBox?>
<?import javafx.scene.text.Font?>

<AnchorPane prefHeight="764.0" prefWidth="901.0" xmlns="http://javafx.com/javafx/11.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="Views.menuController">
   <children>
      <AnchorPane layoutY="2.0" prefHeight="764.0" prefWidth="951.0">
         <children>
            <HBox prefHeight="100.0" prefWidth="746.0" spacing="20.0">
               <children>
                  <Label lineSpacing="10.0" text="Welcom!">
                     <font>
                        <Font size="55.0" />
                     </font>
                  </Label>
                  <Label fx:id="eNameLabel" lineSpacing="10.0" prefHeight="81.0" prefWidth="244.0" text="Label">
                     <font>
                        <Font size="55.0" />
                     </font>
                  </Label>
               </children>
            </HBox>
            <Button fx:id="LogOutButton" layoutX="768.0" layoutY="704.0" mnemonicParsing="false" onAction="#logOutButtonPushed" prefHeight="46.0" prefWidth="176.0" text="Log Out" />
            <Button fx:id="employeeListButton" layoutX="74.0" layoutY="301.0" mnemonicParsing="false" prefHeight="81.0" prefWidth="215.0" text="Employee List" />
            <Button fx:id="productListButton" layoutX="368.0" layoutY="301.0" mnemonicParsing="false" prefHeight="81.0" prefWidth="215.0" text="Products List" />
            <Button fx:id="ingredientListButton" layoutX="661.0" layoutY="301.0" mnemonicParsing="false" prefHeight="81.0" prefWidth="215.0" text="Ingredients List" />
            <Label fx:id="clockLabel" layoutX="74.0" layoutY="710.0" text="Clock" />
            <Button fx:id="addEmployeeButton" layoutX="74.0" layoutY="439.0" mnemonicParsing="false" prefHeight="81.0" prefWidth="215.0" text="Add Employee" />
            <Button fx:id="addProductButton" layoutX="368.0" layoutY="439.0" mnemonicParsing="false" prefHeight="81.0" prefWidth="215.0" text="Add Products" />
            <Button fx:id="addIngreidentButton" layoutX="661.0" layoutY="439.0" mnemonicParsing="false" prefHeight="81.0" prefWidth="215.0" text="Add Ingredients" />
         </children>
      </AnchorPane>
   </children>
</AnchorPane>

When I run the program, the clockLabel stays 'clock' and does not change. It also does not give me any error. When I put clock(); in a constructor I made later, it gave me a nullPointerException error at this.clockLabel.setText(dateFormat.format(currentDate));

I tried getting rid of this in this.clockLabel.setText(dateFormat.format(currentDate)); but it didnt work either.

Answer 1

An initialize method taking parameters is only considered, if it's overriding the method from Initializable. In your case the controller class does not implement Initializable, so FXMLLoader only looks for an initialize() method. Either remove the parameters of the method or add implements Initializable to the class.

As for the constructor resulting in a NPE: the injection of the fields happens after the constructor completes in the lifecycle of the controller:

1. FXMLLoader.load is entered
2. Parsing the fxml the loader encounters the fx:controller attribute and uses reflection to create a instance of the controller.
3. The fields are injected based on their fx:ids
4. The FXMLLoader.load returns.

Answer 2

In addition to Fabian's answer - you can also use the @FXML annotation to make sure the correct method is used:

@FXML
private void initialize() {
    ...
}