JavaFX - controller initialize method gives null pointer exception

Question

I have recently started working with JavaFX and I've got a kind of a problem with controller.

My problem is like this: 1) I've got fxml file in project.startup and it name is loginTab.fxml 2) Controller of this window is in project.startup.controllers and it is called LoginTabController

When I would like to set a disable property on Button (or add a listener to Toggle Group) in initialize method of my controller I've got null pointer exception. Stack trace shows that at the beggining of initialize() is null pointer.

Below I am presenting my code which caused this horrible situation. In fact I was looking for some solution but I can't find anything.

I also have checked if name is spelled propely but unfortunately it is correct.

1) First code sample is how I am loading my page:

 try{
     FXMLLoader fxmlLoader = new FXMLLoader(getClass().getResource("/project/startup/loginTab.fxml"));
     Parent root = fxmlLoader.load();
     Stage stage = new Stage();
     stage.initModality(Modality.APPLICATION_MODAL);
     stage.initStyle(StageStyle.DECORATED);
     stage.setTitle("System Main Menu");
     stage.setScene(new Scene(root));  
     stage.show();
 } catch(Exception ex){
     ex.printStackTrace();
 }

2) Element of my page

 <GridPane xmlns:fx="http://javafx.com/fxml/1" fx:controller="projectgotham.startup.controllers.LoginTabController" prefHeight="200" prefWidth="500" alignment="center" hgap="20" vgap="20">
    <fx:define>
        <ToggleGroup fx:id = "typeOfLogin"/>
    </fx:define>
    <VBox spacing="5" GridPane.columnIndex="0" GridPane.rowIndex="0">
        <children>
            <Label>Choose type of login</Label>
            <RadioButton text="Face" toggleGroup="$typeOfLogin" selected = "true" userData = "Face"/>
            <RadioButton text="Fingerprint" toggleGroup="$typeOfLogin" userData = "Fingerprint"/>
            <RadioButton text="Face and Fingerprint" toggleGroup="$typeOfLogin" userData = "Face and Fingerprint"/> 
            <RadioButton text="Admin" toggleGroup="$typeOfLogin" userData = "Admin"/>
        </children>
    </VBox>
    <VBox spacing="15" GridPane.columnIndex="0" GridPane.rowIndex="1">
        <children>
            <Label>Current login progress</Label>
            <ProgressBar fx:id = "loginProgressBar" progress="0.30"/>
        </children>
    </VBox> 
    <VBox spacing="20" GridPane.columnIndex="0" GridPane.rowIndex="2">
        <children>
            <Button text="Invoke Login Action" onAction="#handleLoginAction"/>
            <Button fx:id="closeSystemBtn" text="Close System" onAction="#closeSystem"/>
        </children>
    </VBox>
    <VBox spacing="5" GridPane.columnIndex="10" GridPane.rowIndex="0">
        <children>
            <Label>Last loaded image</Label>
            <ImageView fx:id="currentImageViewer" fitHeight="150" fitWidth="200" pickOnBounds="true" preserveRatio="true" visible="true">
            </ImageView>
        </children>
    </VBox>
    <VBox spacing="15" GridPane.columnIndex="10" GridPane.rowIndex="1">
        <children>
            <Button fx:id = "testButton" text="Took a photo" onAction="#testThing"/>
            <Button text="Load a fingerprint image"/>
        </children>
    </VBox>
</GridPane>

3) My controller class

public class LoginTabController implements Initializable {

    /**
     * Initializes the controller class.
     */

    @FXML
    private ToggleGroup typeOfLogin;

    @FXML
    private Button closeSystemBtn;

    @Override
    public void initialize(URL url, ResourceBundle rb) {
        closeSystemBtn.setDisable(true);
    }   


    @FXML
    protected void handleLoginAction(ActionEvent event){

        try{
            FXMLLoader fxmlLoader = new FXMLLoader(getClass().getResource("/projectgotham/startup/LoginIdentification.fxml"));
            Parent root = fxmlLoader.load();
            Stage stage = new Stage();
            stage.initModality(Modality.APPLICATION_MODAL);
            stage.initStyle(StageStyle.DECORATED);
            stage.setTitle("Finish login action");
            stage.setScene(new Scene(root));  
            stage.show();
        } catch(Exception ex){
            ex.printStackTrace();
            Logger.getRootLogger().error("Can't handle action connected with login : " + ex.getMessage());
        }
    }

    @FXML
    protected void closeSystem(ActionEvent event){
        Stage closeStage = (Stage) closeSystemBtn.getScene().getWindow();
        closeStage.close();
    }

    @FXML
    protected void testThing(ActionEvent event){
        typeOfLogin.selectedToggleProperty().addListener(new ChangeListener<Toggle>(){
            @Override
            public void changed(ObservableValue<? extends Toggle> observable, Toggle oldValue, Toggle newValue) {
                System.out.println(typeOfLogin.getSelectedToggle().getUserData().toString());
            }

        });

    }

}

I would be pleased if you could help me with this null pointer exception...

EDIT:

Stack trace:

at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2601)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2579)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2441)
at javafx.fxml.FXMLLoader.access$2700(FXMLLoader.java:103)
at javafx.fxml.FXMLLoader$IncludeElement.constructValue(FXMLLoader.java:1143)
at javafx.fxml.FXMLLoader$ValueElement.processStartElement(FXMLLoader.java:746)
at javafx.fxml.FXMLLoader.processStartElement(FXMLLoader.java:2707)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2527)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2441)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2409)
at projectgotham.startup.Startup$2.handle(Startup.java:60)
at projectgotham.startup.Startup$2.handle(Startup.java:55)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
at javafx.event.Event.fireEvent(Event.java:198)
at javafx.scene.Node.fireEvent(Node.java:8413)
at javafx.scene.control.Button.fire(Button.java:185)
at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.event.Event.fireEvent(Event.java:198)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3757)
at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:380)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:294)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$354(GlassViewEventHandler.java:416)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:415)
at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
at com.sun.glass.ui.View.notifyMouse(View.java:937)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
at projectgotham.startup.controllers.LoginTabController.initialize(LoginTabController.java:45)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2548)
... 57 more

Which null pointer exception? Can you edit your question to include the stack trace? — James_D
– James_D, Commented Sep 23, 2016 at 16:53
And line 60 of Startup.java is Parent root = fxmlLoader.load();, line 45 of LoginTabController.java is closeSystemBtn.setDisable(true);, and the FXML you posted is loginTab.fxml, correct? — James_D
– James_D, Commented Sep 23, 2016 at 17:42
what if you comment or delete closeSystemBtn.setDisable(true); and run it again, do you still get exception? — Tomasz Mularczyk
– Tomasz Mularczyk, Commented Sep 23, 2016 at 17:49
James_D true, Tomasz Mularczyk no I don't get this exception. — Thomas Clancy
– Thomas Clancy, Commented Sep 23, 2016 at 18:13
Obviously closeSystemBtn is null, though it should not be because the fx:id is correct and you have the @FXML annotation. I think the next thing I would try is to clean and rebuild your project (details of how depend on your IDE). This is to make sure the latest version of your FXML has been deployed to the build directory. (And, you know, make sure the FXML is saved, etc...) — James_D
– James_D, Commented Sep 23, 2016 at 18:58

GOXR3PLUS · Accepted Answer · 2016-09-23 22:03:07Z

1

I add this Answer in case you are using Eclipse.With Eclipse the differences of the file that you save using SceneBuilder are not synchronized.

So every time you save the fxml file using SceneBuilder what you have to do is reopen it in a Tab.What i mean:

1)

Say for example you have 4 tabs opened in the project you are currently working.If one of those Tabs is a reference to the fxml file,then every time you save the fxml file from SceneBuilder go select another tab and then select again the Tab which is referencing to the FXML file.

or

2)

If no Tab is opened in the Project that is referencing to the FXML file then go into the project and open the FXML file to a new Tab and do the 1.

Example Image

Finnally

You have do to 1 or 2->1 every time you save the FXML.That's Eclipse :)

edited Sep 23, 2016 at 22:03

answered Sep 23, 2016 at 21:58

GOXR3PLUS

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1 Comment

Tomasz Mularczyk Over a year ago

I rember me having to do that also.

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