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Java FX error when i want to run the application [duplicate]

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What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 6 years ago.
This is my Main Class
package application;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.stage.Stage;
import javafx.scene.Parent;
import javafx.scene.Scene;
public class Main extends Application {
#Override
public void start(Stage primaryStage) {
try {
Parent root = FXMLLoader.load(getClass().getResource("application/anwendung.fxml"));
primaryStage.setTitle("Benutzerverwaltung");
root.getStylesheets().add(getClass().getResource("application.css").toExternalForm());
primaryStage.setScene(new Scene(root));
primaryStage.show();
} catch(Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
launch(args);
}
}
This is my Controller class
package application;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.Node;
import javafx.scene.control.Button;
import javafx.scene.input.InputEvent;
import javafx.stage.Stage;
class AnwendungsController {
#FXML
public Button closeButton;
#FXML
public void handleCloseButtonAction(ActionEvent event) {
Stage stage = (Stage) closeButton.getScene().getWindow();
stage.close();
}
}
And this is my fxml file
<?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.text.Font?>
<AnchorPane prefHeight="140.0" prefWidth="350.0" xmlns="http://javafx.com/javafx/8.0.60" xmlns:fx="http://javafx.com/fxml/1" fx:controller="application.AnwendungsController">
<children>
<Button fx:id="closeButton" layoutX="18.0" layoutY="100.0" mnemonicParsing="false" onAction="#handleCloseButtonAction" onMouseClicked="#onMouseClickedCancelBtn" prefHeight="26.0" prefWidth="77.0" text="Abbrechen" />
<Label layoutX="10.0" layoutY="27.0" prefHeight="27.0" prefWidth="342.0" text="Sie können das System nun verwenden" textAlignment="CENTER" textOverrun="CLIP">
<font>
<Font name="System Bold" size="18.0" />
</font>
</Label>
</children>
</AnchorPane>
How can I fix it? I try everything from here JavaFX "Location is required." even though it is in the same package
UPDATE:
java.lang.NullPointerException: Location is required.
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3207)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3175)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3148)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3124)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3104)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:3097)
at application.Main.start(Main.java:20)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$162(LauncherImpl.java:863)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$175(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
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(Unknown Source)

Two problems exist:
1)The File path
2)The Controller was not set properly
Recommendation:
If you are using SceneBuilder, when you want to see what your controller might look like, you can go to View -> Show Sample Controller Skeleton.
Solution
Main class:
package application;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.stage.Stage;
import javafx.scene.Parent;
import javafx.scene.Scene;
public class Main extends Application {
#Override
public void start(Stage primaryStage) {
try {
System.out.println(getClass().getResource("anwendung.fxml").getPath());
//other solution
//FXMLLoader loader = new FXMLLoader(getClass().getResource("anwendung.fxml"));
//Parent root = loader.load();
//Keep in mind that you are calling a static method
Parent root = FXMLLoader.load(getClass().getResource("anwendung.fxml"));
primaryStage.setTitle("Benutzerverwaltung");
root.getStylesheets().add(getClass().getResource("application.css").toExternalForm());
primaryStage.setScene(new Scene(root));
primaryStage.show();
} catch (Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
launch(args);
}
}
Controller:
package application;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.Button;
import javafx.scene.input.MouseEvent;
public class AnwendungsController {
#FXML
private Button closeButton;
#FXML
void handleCloseButtonAction(ActionEvent event) {
}
#FXML
void onMouseClickedCancelBtn(MouseEvent event) {
}
}
FXML:
<?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.text.Font?>
<AnchorPane prefHeight="140.0" prefWidth="350.0" xmlns="http://javafx.com/javafx/8.0.60" xmlns:fx="http://javafx.com/fxml/1" fx:controller="application.AnwendungsController">
<children>
<Button fx:id="closeButton" layoutX="18.0" layoutY="100.0" mnemonicParsing="false" onAction="#handleCloseButtonAction" onMouseClicked="#onMouseClickedCancelBtn" prefHeight="26.0" prefWidth="77.0" text="Abbrechen" />
<Label layoutX="10.0" layoutY="27.0" prefHeight="27.0" prefWidth="342.0" text="Sie können das Systema nun verwenden" textAlignment="CENTER" textOverrun="CLIP">
<font>
<Font name="System Bold" size="18.0" />
</font>
</Label>
</children>
</AnchorPane>

JavaFX - include fxml with an event in it

I'm currently trying to implements a very basic application with JavaFX just to do some tests. The final goal here is to implement an interface separated in severals parts, and each part will have its own .fxm and controller.
For the beginning, I've tried to develop a basic application with this architecture :
Project explorer
I have a main VueGlobale.fxml file which include another .fxml file clavier.fxml :
VueGlobale.fxml
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.layout.HBox?>
<?import javafx.scene.layout.VBox?>
<VBox
maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="529.0" xmlns="http://javafx.com/javafx/8.0.121" xmlns:fx="http://javafx.com/fxml/1">
<children>
<fx:include source="clavier.fxml" fx:id="clavier" />
</children>
</VBox>
clavier.fxml
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.layout.AnchorPane?>
<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.141" xmlns:fx="http://javafx.com/fxml/1" fx:controller="controllers.ClavierController">
<children>
<Button layoutX="274.0" layoutY="188.0" mnemonicParsing="false" onAction="#ajouterDo" text="Button" />
</children>
</AnchorPane>
An here's the ClavierController.fxml :
package controllers;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import model.Model;
public class ClavierController {
private Model model;
public ClavierController(Model m) {
this.model = m;
}
#FXML
public void ajouterDo(ActionEvent e){
System.out.println("Click !");
this.model.doSomething();
}
}
Model
package model;
public class Model {
public void doSomething() {
System.out.println("Model !");
}
}
Main
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;
public class Main extends Application {
#Override
public void start(Stage primaryStage) throws Exception{
FXMLLoader loader = new FXMLLoader();
loader.setLocation(getClass().getResource("views/VueGlobale.fxml"));
Parent root = loader.load();
primaryStage.setTitle("Test");
primaryStage.setScene(new Scene(root, 300, 275));
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}
The problem is : I don't know what to do in my main so that I can give to my clavier.fxml a ClavierController(Model m). (It's working with a controller without parameters, but what if I need to precise parameters ?)
Here's the StackTrace if it could help you :
Exception in Application start method
java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)
at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at sun.launcher.LauncherHelper$FXHelper.main(Unknown Source)
Caused by: java.lang.RuntimeException: Exception in Application start method
at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$155(LauncherImpl.java:182)
at java.lang.Thread.run(Unknown Source)
Caused by: javafx.fxml.LoadException:
/J:/Programming/Telecom%20Nancy/S3/Test/bin/views/clavier.fxml:6
/J:/Programming/Telecom%20Nancy/S3/Test/bin/views/VueGlobale.fxml:9
at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2601)
at javafx.fxml.FXMLLoader.access$700(FXMLLoader.java:103)
at javafx.fxml.FXMLLoader$ValueElement.processAttribute(FXMLLoader.java:932)
at javafx.fxml.FXMLLoader$InstanceDeclarationElement.processAttribute(FXMLLoader.java:971)
at javafx.fxml.FXMLLoader$Element.processStartElement(FXMLLoader.java:220)
at javafx.fxml.FXMLLoader$ValueElement.processStartElement(FXMLLoader.java:744)
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.access$2700(FXMLLoader.java:103)
at javafx.fxml.FXMLLoader$IncludeElement.constructValue(FXMLLoader.java:1143)
at javafx.fxml.FXMLLoader$ValueElement.processStartElement(FXMLLoader.java:746)
at javafx.fxml.FXMLLoader.processStartElement(FXMLLoader.java:2707)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2527)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2441)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2409)
at Main.start(Main.java:14)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$162(LauncherImpl.java:863)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$175(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
... 1 more
Caused by: java.lang.InstantiationException: controllers.ClavierController
at java.lang.Class.newInstance(Unknown Source)
at sun.reflect.misc.ReflectUtil.newInstance(Unknown Source)
at javafx.fxml.FXMLLoader$ValueElement.processAttribute(FXMLLoader.java:927)
... 23 more
Caused by: java.lang.NoSuchMethodException: controllers.ClavierController.<init>()
at java.lang.Class.getConstructor0(Unknown Source)
... 26 more
Exception running application Main
Thank you in advance for your help and for your time, have a good day.
EDIT :
By including several fxml, i mean this :
VueGlobale.fxml
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.layout.HBox?>
<?import javafx.scene.layout.VBox?>
<VBox
maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="529.0" xmlns="http://javafx.com/javafx/8.0.121" xmlns:fx="http://javafx.com/fxml/1">
<children>
<fx:include source="viewtop.fxml" fx:id="top" />
</children>
<children>
<fx:include source="clavier.fxml" fx:id="clavier" />
</children>
<children>
<fx:include source="viewbottom.fxml" fx:id="bottom" />
</children>
</VBox>
So I have three .fxml file included in my VueGlobale.fxml. Let us supposed that all this .fxml have their own controller (ClavierController.java, TopController.java, BottomController.java). All these controllers needs the model. What should I do in my main factory ? Something like this doesn't work :
import controllers.ClavierController;
import controllers.TopController;
import controllers.BottomController;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;
import model.Model;
public class Main extends Application {
#Override
public void start(Stage primaryStage) throws Exception{
Model m = new Model();
FXMLLoader loader = new FXMLLoader();
loader.setLocation(getClass().getResource("views/VueGlobale.fxml"));
loader.setControllerFactory(ic -> new ClavierController(m));
loader.setControllerFactory(ic -> new TopController(m));
loader.setControllerFactory(ic -> new BottomController(m));
Parent root = loader.load();
primaryStage.setTitle("Test");
primaryStage.setScene(new Scene(root, 300, 275));
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}

ButtonPane.fxml
----------------
<?xml version="1.0" encoding="UTF-8"?>
<?import com.jfoenix.controls.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.layout.AnchorPane?>
<AnchorPane fx:id="buttonPane" maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" prefHeight="30.0" prefWidth="700.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="com.everest.amcu.ButtonPaneController">
<children>
<HBox fx:id="hboxButton" alignment="CENTER_LEFT" maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" spacing="5.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
<children>
<JFXButton fx:id="btnAdd" maxHeight="1.7976931348623157E308" maxWidth="100.0" prefWidth="50.0" text="Add" HBox.hgrow="ALWAYS" />
<JFXButton fx:id="btnEdit" layoutX="10.0" layoutY="10.0" maxHeight="1.7976931348623157E308" maxWidth="100.0" prefWidth="50.0" text="Edit" HBox.hgrow="ALWAYS" />
<JFXButton fx:id="btnDelete" layoutX="62.0" layoutY="10.0" maxHeight="1.7976931348623157E308" maxWidth="100.0" prefWidth="50.0" text="Delete" HBox.hgrow="ALWAYS" />
<JFXButton fx:id="btnClose" layoutX="114.0" layoutY="10.0" maxHeight="1.7976931348623157E308" maxWidth="100.0" prefWidth="50.0" text="Close" HBox.hgrow="ALWAYS" />
</children>
</HBox>
</children>
</AnchorPane>
PaneOne.fxml
---------------
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.layout.AnchorPane?>
<AnchorPane xmlns:fx="http://javafx.com/fxml/1" fx:controller="com.everest.amcu.PaneOneController">
<fx:include source="ButtonPane.fxml" fx:id="buttonPane" /> </AnchorPane>
ButtonPaneController
--------------------
import java.net.URL;
import java.util.ResourceBundle;
import com.jfoenix.controls.JFXButton;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.HBox;
public class ButtonPaneController implements Initializable {
#FXML
public JFXButton btnClose;
#FXML
public JFXButton btnDelete;
#FXML
public JFXButton btnAdd;
#FXML
public JFXButton btnEdit;
#FXML
private AnchorPane buttonPane;
#FXML
private HBox hboxButton;
#Override
public void initialize(URL location, ResourceBundle resources) {
btnClose.setOnAction(event -> {
System.out.println("In Button Pane");
});
btnAdd.setOnAction(event -> {
System.out.println("In Button Pane");
});
}
public void hideButton(JFXButton... jfxButton) {
for (int i = 0; i < jfxButton.length; i++) {
hboxButton.getChildren().remove(jfxButton[i]);
}
}
}
PaneOneController
------------------
import java.net.URL;
import java.util.ResourceBundle;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
public class PaneOneController implements Initializable {
#FXML
ButtonPaneController buttonPaneController;
#Override
public void initialize(URL location, ResourceBundle resources) {
buttonPaneController.btnAdd.setOnAction(event -> {
System.out.println("In Pane One");
});
}
}
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.stage.Stage;
import javafx.stage.StageStyle;
public class Main extends Application {
public static Stage primaryStage;
public static Label lblTitle;
#Override
public void start(Stage primaryStage) {
try {
Main.primaryStage = primaryStage;
Parent root = FXMLLoader.load(Main.class.getResource("view/PaneOne.fxml"));
Scene scene = new Scene(root);
scene.getStylesheets().add(Main.class.getResource("view/css/application.css").toExternalForm());
primaryStage.setScene(scene);
primaryStage.initStyle(StageStyle.UNDECORATED);
primaryStage.show();
} catch (Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
launch(args);
}
}
Steps of doing this:
Create ButtonPane.fxml and declare id of anchor pane and all the
button.
Create PaneOne.fxml and include Button.fxml using
,important thing is when you include fxml must be
declare id same as anchor pane id of ButtonPane.fxml.
Create ButtonPaneController for initialize variable.
Create PaneOneController and just declare ButtonPaneController using
#FXML annotation.
Run the program, it's working well with action event of button.

The controllerFactory is a property like any other property. If you set its value, it has that value, so it makes no sense to set its value to three different things in three consecutive lines of code.
You can create a controller factory that simply checks the parameter and returns the appropriate controller:
public class Main extends Application {
#Override
public void start(Stage primaryStage) throws Exception{
Model m = new Model();
FXMLLoader loader = new FXMLLoader();
loader.setLocation(getClass().getResource("views/VueGlobale.fxml"));
loader.setControllerFactory(ic -> {
if (ic == ClavierController.class) {
return new ClavierController(m);
} else if (ic == TopController.class) {
return new TopController(m);
} else if (ic == BottomController.class) {
return new BottomController(m) ;
}
throw new IllegalArgumentException("Unexpected controller type: "+ic.getName());
});
Parent root = loader.load();
primaryStage.setTitle("Test");
primaryStage.setScene(new Scene(root, 300, 275));
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}
You can also use reflection to implement logic like "If the supplied controller class has a constructor taking a model, call that constructor and pass the model in, otherwise call the default constructor":
loader.setControllerFactory(ic -> {
try {
for (Constructor<?> c : ic.getConstructors()) {
if (c.getParameterCount() == 1 && c.getParameterTypes()[0]==Model.class) {
return c.newInstance(m);
}
}
return ic.newInstance();
} catch (Exception e) {
// fatal...
throw new RuntimeException(e);
}
});
This is all a bit heavy-handed for what you are trying to achieve, though. You are merely trying to pass a model to the nested controllers (the controllers for the FXML files loaded via <fx:include>). The documentation explicitly provides an injection-based approach for this.
Specifically, if your "main" FXML adds fx:ids to the <fx:include>s, then the controllers can be injected into the main controller. So you can do something like:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.layout.HBox?>
<?import javafx.scene.layout.VBox?>
<VBox
maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="529.0" xmlns="http://javafx.com/javafx/8.0.121" xmlns:fx="http://javafx.com/fxml/1">
<children>
<fx:include source="viewtop.fxml" fx:id="top" />
</children>
<children>
<fx:include source="clavier.fxml" fx:id="clavier" />
</children>
<children>
<fx:include source="viewbottom.fxml" fx:id="bottom" />
</children>
</VBox>
Now define a "main" controller for this FXML file:
public class MainController {
#FXML
private Parent top ;
#FXML
private Parent clavier ;
#FXML
private Parent bottom ;
#FXML
private TopController topController ;
#FXML
private ClavierController clavierController ;
#FXML
private BottomController bottomController ;
private final Model model ;
public MainController(Model model) {
this.model = model ;
}
#FXML
public void initialize() {
topController.setModel(model);
clavierController.setModel(model);
bottomController.setModel(model);
}
// ...
}
Just define the "nested" controllers with the appropriate methods for setting the model:
public class TopController {
private Model model ;
public void setModel(Model model) {
this.model = model ;
}
#FXML
private void someHandlerMethod(ActionEvent event) {
model.doSomething();
}
}
And finally load your main fxml with:
Model model = new Model();
FXMLLoader loader = new FXMLLoader(getClass().getResource("/path/to/fxml"));
loader.setController(new MainController(model));
Parent root = loader.load();
and it should all be good to go.

Loading multiple FXML-files fails when controllers are defined

I know this question is asked many times, but I can't find a solution, that works for me (actually I can't even see what I am doing wrong).
The basic idea is to load GUI-components when needed. So I structured the GUI in various FXML-Files and implemented controller-classes. Both - FXML-files and classes - are stored in the same package but ther is a package for every component. Every FXML-file is loading and added to the GUI as long as I do not define the controller-class within the FXML-file (fx:controller). If it is defined I will get a LoadException.
For a better understanding here is my code (simplified):
Main.java:
package application;
import application.a.ControllerA;
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;
public class Main extends Application
{
// Button aus MainLayout.fxml
#FXML
private Button button;
#Override
public void start(Stage primaryStage)
{
try
{
BorderPane root = new BorderPane();
Parent contentMain = FXMLLoader.load(getClass().getResource("MainLayout.fxml"));
ControllerA contentA = new ControllerA(root);
root.setTop(contentA.getContent());
root.setCenter(contentMain);
Scene scene = new Scene(root, 400, 400);
scene.getStylesheets().add(getClass().getResource("application.css").toExternalForm());
primaryStage.setScene(scene);
primaryStage.show();
}
catch (Exception e)
{
e.printStackTrace();
}
}
public static void main(String[] args)
{
launch(args);
}
// Event-Handler für den Button -> funktioniert!
#FXML
public void buttonClicked(ActionEvent e)
{
if (!button.getText().equals("NEW"))
{
button.setText("NEW");
}
else
{
button.setText("OLD");
}
}
}
This class is also a controller for the following layout (and it works fins so far):
MainLayout.fxml:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.layout.GridPane?>
<Pane xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="application.Main">
<children>
<Button fx:id="button" mnemonicParsing="false" onAction="#buttonClicked" text="Button" />
</children>
</Pane>
In a sub-package (called a) of application you will find this:
ControllerA.java:
package application.a;
import java.net.URL;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.control.Button;
import javafx.scene.layout.BorderPane;
public class ControllerA
{
private Parent content;
#FXML
private Button buttonA;
public ControllerA(BorderPane root)
{
String sceneFile = "A.fxml";
URL url = null;
try
{
url = getClass().getResource(sceneFile);
content = FXMLLoader.load(url);
}
catch (Exception ex)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public Parent getContent()
{
return content;
}
#FXML
public void clickedA(ActionEvent e)
{
buttonA.setText("Clicked already");
}
}
A.fxml:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.layout.GridPane?>
<Pane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="application.a.ControllerA">
<children>
<Button fx:id="buttonA" layoutX="274.0" layoutY="188.0" mnemonicParsing="false" onAction="#clickedA" text="A" />
</children>
</Pane>
And this is, where it all went wrong:
javafx.fxml.LoadException:
/Z:/BachelorArbeit/Projektdateien/Entwicklung/EclipseWorkspace/Sandbox/bin/application/a/A.fxml:8
at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2601)
at javafx.fxml.FXMLLoader.access$700(FXMLLoader.java:103)
at javafx.fxml.FXMLLoader$ValueElement.processAttribute(FXMLLoader.java:932)
at javafx.fxml.FXMLLoader$InstanceDeclarationElement.processAttribute(FXMLLoader.java:971)
at javafx.fxml.FXMLLoader$Element.processStartElement(FXMLLoader.java:220)
at javafx.fxml.FXMLLoader$ValueElement.processStartElement(FXMLLoader.java:744)
at javafx.fxml.FXMLLoader.processStartElement(FXMLLoader.java:2707)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2527)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2441)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3214)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3175)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3148)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3124)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3104)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:3097)
at application.a.ControllerA.<init>(ControllerA.java:26)
at application.Main.start(Main.java:35)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$162(LauncherImpl.java:863)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$175(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.InstantiationException: application.a.ControllerA
at java.lang.Class.newInstance(Class.java:427)
at sun.reflect.misc.ReflectUtil.newInstance(ReflectUtil.java:51)
at javafx.fxml.FXMLLoader$ValueElement.processAttribute(FXMLLoader.java:927)
... 23 more
Caused by: java.lang.NoSuchMethodException: application.a.ControllerA.<init>()
at java.lang.Class.getConstructor0(Class.java:3082)
at java.lang.Class.newInstance(Class.java:412)
... 25 more
I've tried to fiddle around with the path-String like
"./a/A.fxml"
"/application/a/A.fxml"
"A.fxml"
"a/A.fxml"
...
but nothing worked. I would be quite relieved if someone can halp me with this problem.

You're mixing two different ways of using FXML and controllers. If your FXML file has fx:controller="SomeClass", then the FXMLLoader will instantiate that class and use the instance as a controller: in other words, it makes the FXML create the controller.
On the other hand, your controller's constructor loads the FXML, so you also have the controller creating the UI defined in the FXML.
The reason for the exception is that when the FXMLLoader encounters the fx:controller attribute, it calls the no-argument constructor of the specified class: i.e. in this case it tries to call new ControllerA(). Since there is no such constructor you get the exception:
java.lang.NoSuchMethodException: application.a.ControllerA.<init>()
It's not really clear what the purpose of the BorderPane parameter to the controller's constructor is, as you never use it. However, even if you had an appropriate constructor here, it would cause another problem: loading the FXML would invoke the controller's constructor, which loads the FXML, which would invoke the controller's constructor, etc: you would get a StackOverflowException. If you want to load the FXML from the controller's constructor:
remove the fx:controller attribute from the FXML file
Explicitly set the controller on the FXMLLoader to the current controller instance:
public ControllerA(BorderPane root)
{
String sceneFile = "A.fxml";
URL url = null;
try
{
url = getClass().getResource(sceneFile);
FXMLLoader loader = new FXMLLoader(url);
loader.setController(this);
content = loader.load();
}
catch (Exception ex)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}

I'll show you an minimal working example project and I suggest that you adapt your structure to it.
The folder structure is as follows
Here is the main class
package dynamic.content.javafx;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.layout.GridPane;
import javafx.stage.Stage;
public final class Main extends Application {
#Override
public void start(Stage stage) throws Exception {
Parent root = FXMLLoader.load(getClass().getResource("main.fxml"));
Scene scene = new Scene(root, 300, 200);
stage.setTitle("FXML Welcome");
stage.setScene(scene);
stage.show();
}
public static void main(String[] args) {
launch(args);
}
}
The main controller
package dynamic.content.javafx;
import java.io.IOException;
import java.net.URL;
import java.util.ResourceBundle;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.fxml.Initializable;
import javafx.scene.Parent;
import javafx.scene.control.Button;
import javafx.scene.layout.AnchorPane;
public final class MainController implements Initializable{
#FXML
private Button btnSwitch;
#FXML
private AnchorPane contentPane;
#Override
public void initialize(URL location, ResourceBundle resources) {
// TODO Auto-generated method stub
}
private boolean swtch = false;
#FXML
public void handleContentSwitch() throws IOException{
Parent contentNode = null;
if(swtch){
System.out.println("loading content A");
contentNode = FXMLLoader.load(getClass().getResource("./content/content_a.fxml"));
}else{
System.out.println("loading content B");
contentNode = FXMLLoader.load(getClass().getResource("./content/content_b.fxml"));
}
contentPane.getChildren().clear();
contentPane.getChildren().add(contentNode);
swtch = !swtch;
}
}
The main FXML
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<VBox alignment="TOP_CENTER" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="200.0" prefWidth="300.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="dynamic.content.javafx.MainController">
<children>
<Button fx:id="btnSwitch" onAction="#handleContentSwitch" alignment="CENTER" contentDisplay="CENTER" mnemonicParsing="false" text="Switch Content" />
<AnchorPane fx:id="contentPane" prefHeight="150.0" prefWidth="300.0" />
</children>
</VBox>
Let's say we have content A and B we need to create a controller and a FXML every one of them
package dynamic.content.javafx.content;
import java.net.URL;
import java.util.ResourceBundle;
import javafx.fxml.Initializable;
import javafx.fxml.FXML;
import javafx.scene.control.Label;
public class ContentAController implements Initializable{
#FXML
private Label labl;
#Override
public void initialize(URL location, ResourceBundle resources) {
labl.setText("Content A");
}
}
And now the corresponding FXML
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="150.0" prefWidth="300.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="dynamic.content.javafx.content.ContentAController">
<children>
<Label fx:id="labl" alignment="CENTER" contentDisplay="CENTER" text="Label" textAlignment="CENTER" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0" />
</children>
</AnchorPane>
Here follows the second controller
package dynamic.content.javafx.content;
import java.net.URL;
import java.util.ResourceBundle;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Label;
public class ContentBController implements Initializable{
#FXML
private Label labl;
#Override
public void initialize(URL location, ResourceBundle resources) {
labl.setText("Content B");
}
}
and the second FXML
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="150.0" prefWidth="300.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="dynamic.content.javafx.content.ContentBController">
<children>
<Label fx:id="labl" alignment="CENTER" contentDisplay="CENTER" text="Label" textAlignment="CENTER" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0" />
</children>
</AnchorPane>
If you know press the button the content will be loaded dynamically
If you have any questions, just let me know :-)

JavaFX Starter: Modifying Label Text on other window from Main Window

I'm a new javaFx with Scenebuilder and MVC starter.
I have a problem as below:
I tried to make a main window to alert a new window. And I tried to midified the label text in that alert window. But I cannot do that. And I got this error:
Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1774)
at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1657)
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:8411)
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$MouseEventNotification.run(GlassViewEventHandler.java:352)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:275)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$355(GlassViewEventHandler.java:388)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:387)
at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
at com.sun.glass.ui.View.notifyMouse(View.java:937)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$149(WinApplication.java:191)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1771)
... 48 more
Caused by: java.lang.NullPointerException
at controller.AlertController.setAlertLabel(AlertController.java:36)
at controller.MainController.onMainButtonClicked(MainController.java:24)
... 58 more
I have a main window with maincontroller, alertController and main.fxml and alert.fxml as below:
Main:
package app;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;
public class Main extends Application {
#Override
public void start(Stage primaryStage) throws Exception{
Parent root = FXMLLoader.load(getClass().getResource("../view/Main.fxml"));
primaryStage.setTitle("Hello World");
primaryStage.setScene(new Scene(root));
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}
Main Controller:
package controller;
import javafx.fxml.FXML;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
public class MainController {
AlertController alertController = new AlertController();
#FXML
public Label mainLabel;
#FXML
public TextField mainTextField;
#FXML
public Button mainButton;
#FXML
public void onMainButtonClicked() {
alertController.displayAlert();
alertController.setAlertLabel("Hello from MainController!");
}
}
Main.fxml:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.layout.HBox?>
<?import javafx.scene.layout.VBox?>
<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.60" xmlns:fx="http://javafx.com/fxml/1" fx:controller="controller.MainController">
<children>
<VBox prefHeight="400.0" prefWidth="600.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
<children>
<HBox alignment="CENTER" prefHeight="154.0" prefWidth="600.0">
<children>
<Label fx:id="mainLabel" alignment="CENTER" contentDisplay="TOP" prefHeight="31.0" prefWidth="115.0" text="Main Text" />
</children>
</HBox>
<HBox alignment="CENTER" centerShape="false" layoutX="10.0" layoutY="10.0">
<children>
<TextField fx:id="mainTextField" alignment="TOP_LEFT" prefHeight="25.0" prefWidth="331.0" />
</children>
</HBox>
<HBox alignment="CENTER" layoutX="10.0" layoutY="10.0" prefHeight="100.0" prefWidth="200.0">
<children>
<Button fx:id="mainButton" mnemonicParsing="false" onAction="#onMainButtonClicked" text="Display Alert && Set Message Text" />
</children>
</HBox>
</children>
</VBox>
</children>
</AnchorPane>
AlertController:
package controller;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.stage.Stage;
import java.io.IOException;
public class AlertController {
Stage window;
#FXML
public Label alertLabel;
#FXML
Button alertButton;
public void displayAlert() {
try {
window = new Stage();
Parent root = FXMLLoader.load(getClass().getResource("../view/Alert.fxml"));
Scene scene = new Scene(root);
window.setScene(scene);
window.setTitle("Alert");
window.show();
} catch (IOException e) {
e.printStackTrace();
}
}
public void setAlertLabel(String str) {
alertLabel.setText(str);
}
#FXML
public void onAlertButtonClicked() {
window.close();
}
}
And Alert.fxml:
<?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.layout.VBox?>
<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="210.0" prefWidth="380.0" xmlns="http://javafx.com/javafx/8.0.60" xmlns:fx="http://javafx.com/fxml/1" fx:controller="controller.AlertController">
<children>
<VBox prefHeight="210.0" prefWidth="380.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
<children>
<HBox alignment="BOTTOM_CENTER" prefHeight="100.0" prefWidth="200.0">
<children>
<Label fx:id="alertLabel" text="Alert Message" />
</children>
</HBox>
<HBox alignment="CENTER" prefHeight="100.0" prefWidth="200.0">
<children>
<Button fx:id="alertButton" mnemonicParsing="false" onAction="#onAlertButtonClicked" text="Close" />
</children>
</HBox>
</children>
</VBox>
</children>
</AnchorPane>
Please kindly help me solve this problems and explain me why this doesn't work. Thank you for you suggestions.

There are two instances of AlertController: the one you create in MainController with
AlertController alertController = new AlertController();
and the one that is created by the FXMLLoader when you load Alert.fxml in displayAlert().
The #FXML-annotated fields are initialized by the FXMLLoader on the instance it creates. However, you are calling setAlertLabel(...) on an instance of AlertController that was not created by the FXMLLoader. So when you call
alertController.setAlertLabel("Hello from MainController!");
the alertLabel belonging to alertController has not been initialized, and you get a null pointer exception.
Simple Solution
The easiest fix is to load Alert.fxml in MainController, and retrieve the correct controller instance:
public class MainController {
#FXML
public Label mainLabel;
#FXML
public TextField mainTextField;
#FXML
public Button mainButton;
#FXML
public void onMainButtonClicked() {
FXMLLoader loader = new FXMLLoader(getClass().getResource("../view/Alert.fxml"));
Parent root = loader.load();
AlertController alertController = loader.getController();
alertController.setAlertLabel("Hello from MainController!");
Scene scene = new Scene(root);
window.setScene(scene);
window.setTitle("Alert");
window.show();
}
}
and remove the displayAlert() method from AlertController.
Custom Component Solution
An alternative, which is structurally a bit closer to your original, is to replace the AlertController with a custom component.
Alert.fxml (note the change to the root element, and that fx:controller has been removed):
<?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.layout.VBox?>
<fx:root type="AnchorPane" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="210.0" prefWidth="380.0" xmlns="http://javafx.com/javafx/8.0.60" xmlns:fx="http://javafx.com/fxml/1" >
<children>
<VBox prefHeight="210.0" prefWidth="380.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
<children>
<HBox alignment="BOTTOM_CENTER" prefHeight="100.0" prefWidth="200.0">
<children>
<Label fx:id="alertLabel" text="Alert Message" />
</children>
</HBox>
<HBox alignment="CENTER" prefHeight="100.0" prefWidth="200.0">
<children>
<Button fx:id="alertButton" mnemonicParsing="false" onAction="#onAlertButtonClicked" text="Close" />
</children>
</HBox>
</children>
</VBox>
</children>
</fx:root>
AlertController.java:
package controller;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.stage.Stage;
import java.io.IOException;
public class AlertController extends AnchorPane {
Stage window;
#FXML
public Label alertLabel;
#FXML
Button alertButton;
public AlertController() {
window = new Stage();
try {
FXMLLoader loader = new FXMLLoader(getClass().getResource("../view/Alert.fxml"));
loader.setController(this);
loader.setRoot(this);
loader.load();
Scene scene = new Scene(this);
window.setScene(scene);
window.setTitle("Alert");
} catch (IOException e) {
e.printStackTrace();
}
}
public void displayAlert() {
window.show();
}
public void setAlertLabel(String str) {
alertLabel.setText(str);
}
#FXML
public void onAlertButtonClicked() {
window.close();
}
}
and now your main controller can look like this:
package controller;
import javafx.fxml.FXML;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
public class MainController {
AlertController alertController = new AlertController();
#FXML
public Label mainLabel;
#FXML
public TextField mainTextField;
#FXML
public Button mainButton;
#FXML
public void onMainButtonClicked() {
alertController.displayAlert();
alertController.setAlertLabel("Hello from MainController!");
}
}

How to send Message from FXML controller class to Main Application class

Hello stackoverflowers,
I have a question "I have an fxml file "CrawlerView.fxml" and its controller "CrawlerController.java" and a main Application class I want to send Message(database insert) from controller class to main Application class(because i cant do business logic in GUI/fxml controller class) . So my question is: Is it possible to send message from fxml controller class to main application class"
code is below
any help
thanx in advance`
Crawler.java
package app.model.main;
import java.io.IOException;
import java.sql.Statement;
import java.util.Stack;
import javafx.application.Application;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextField;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;
public class Crawler extends Application {
private Stage MStage;
private BorderPane rootLayout;
#FXML Button SEARCH;
#FXML TextField URL;
static Conection conection;
static url_entries URLS;//self implemented classes
static word_count count;//self implemented classes
static Statement stmt;
//static public Stack DATABASE;
public static void test(){}
public static void main(String[] args)
{
launch(args);
}
#Override
public void start(Stage MStage)
{
try {
FXMLLoader RootLoader = new FXMLLoader();
FXMLLoader CrawlerLoader = new FXMLLoader();
RootLoader.setLocation(Crawler.class.getResource("view/RootView.fxml"));
CrawlerLoader.setLocation(Crawler.class.getResource("view/CrawlerView.fxml"));
rootLayout = (BorderPane) RootLoader.load();
AnchorPane CV = (AnchorPane) CrawlerLoader.load();
rootLayout.setCenter(CV);
// Show the scene containing the root layout.
Scene scene = new Scene(rootLayout);
MStage.setScene(scene);
MStage.show();
} catch (IOException e)
{
e.printStackTrace();
}
}
}
CrawlerView.fxml
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.effect.*?>
<?import javafx.scene.text.*?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.layout.AnchorPane?>
<AnchorPane prefHeight="628.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.40" xmlns:fx="http://javafx.com/fxml/1" fx:controller="app.model.main.CrawlerController">
<children>
<SplitPane dividerPositions="0.14424635332252836" layoutX="8.0" layoutY="-2.0" orientation="VERTICAL" prefHeight="628.0" prefWidth="600.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
<items>
<AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="100.0" prefWidth="160.0">
<children>
<Label layoutX="105.0" layoutY="14.0" prefHeight="52.0" prefWidth="388.0" text="Khurasani Web Crawler" textFill="#792323">
<font>
<Font name="Bauhaus 93" size="34.0" />
</font>
</Label>
</children>
</AnchorPane>
<AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="100.0" prefWidth="160.0">
<children>
<TextField id="URL" fx:id="URL" alignment="CENTER" blendMode="DARKEN" layoutX="110.0" layoutY="25.0" prefHeight="34.0" prefWidth="359.0" text="Enter URL">
<font>
<Font name="Berlin Sans FB Demi Bold" size="17.0" />
</font>
<effect>
<InnerShadow choke="0.56" color="#722424" height="26.93" radius="12.965" width="26.93" />
</effect>
</TextField>
<Button id="SEARCH" fx:id="SEARCH" layoutX="247.0" layoutY="82.0" mnemonicParsing="false" prefHeight="27.0" prefWidth="79.0" text="Search" textFill="#5e2929">
<font>
<Font name="Arial Black" size="15.0" />
</font>
</Button>
</children>
</AnchorPane>
</items>
</SplitPane>
CrawlerController
package app.model.main;
import java.net.URL;
import java.sql.Statement;
import java.util.ResourceBundle;
import java.util.Stack;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Button;
import javafx.scene.control.TextField;
public class CrawlerController implements Initializable
{
#FXML Button SEARCH;
#FXML TextField URL;
#Override // This method is called by the FXMLLoader when initialization is complete
public void initialize(URL fxmlFileLocation, ResourceBundle resources) {
assert SEARCH != null : "fx:id=\"myButton\" was not injected: check your FXML file 'simple.fxml'.";
SEARCH.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent event)
{
//How to send message to main application class
}
});}
}