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Launch error while running javafx program

I am running a simple javafx program on eclipse IDE. However, whenever I run my code, a launch error is displayed. There is no description of the error by the IDE and I am not sure what is causing that.
Also, I have e(fx)clipse and Gluon plugin installed.
My code is very simple and I don't think that it is causing this error, however, I have attached it below for reference.
package application;
import Menus.MainMenu;
import javafx.application.Application;
import javafx.stage.Stage;
public class Main extends Application {
#Override
public void start(Stage primaryStage) {
try {
MainMenu mainMenu = new MainMenu();
primaryStage = mainMenu.getMainStage();
primaryStage.show();
} catch (Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
launch(args);
}
}
Code for MainMenu is
package Menus;
import javafx.scene.Scene;
import javafx.scene.layout.AnchorPane;
import javafx.stage.Stage;
public class MainMenu {
private static final int HEIGHT = 600;
private static final int WIDTH = 800;
private AnchorPane mainPane;
private Scene mainScene;
private Stage mainStage;
public MainMenu() {
mainPane = new AnchorPane();
mainScene = new Scene(mainPane);
mainStage = new Stage();
mainStage.setScene(mainScene);
mainStage.setFullScreen(true);
}
public Stage getMainStage() {
return mainStage;
}
}

Check the log file for the exact error and resolve it at :
C:\app\eclipse\configuration\
Check if the JRE is properly configured in eclipse as well as environment variables.
Do not just click on the run button, check if you are running the proper program path by clicking on the arrow next to run. (This is a common problem with beginners)
If you find everything else troublesome, try re-installing the IDE and running a simple hello world. If the problem persists, it is something to do with the environment variables or your eclipse setup.

TextField null pointer exception [duplicate]

This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 5 years ago.
I don't know if this helps but if I run this code in which i have commented out the setText lines it returns "pointer ok" which suggests that the extCon.setStartValues is pointing to the correct method, although as you pointed out this is another instance of the from and not the one I actually want to populate.
package extrusion;
//import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.Button;
import javafx.scene.control.TextField;
public class ExtrusionController {
private double weight = 16.0;
private double rpm = 30.0;
private double time = 0.5;
#FXML
private TextField timeSecs;
#FXML
private TextField revsPerMin;
#FXML
private TextField sampleWeight;
// #FXML
// void 838383(ActionEvent event) {
//
// }
#FXML
public void setStartValues(){
System.out.println("pointer ok");
// sampleWeight.setText("" + weight);
// revsPerMin.setText("" + rpm);
// timeSecs.setText("" + time);
}
}
package extrusion;
import java.io.IOException;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.layout.AnchorPane;
import javafx.stage.Stage;
public class ExtrusionApp extends Application {
private AnchorPane extrusionForm;
private ExtrusionController extrusionController;
public void start(Stage primaryStage) {
ExtrusionController extCon = new ExtrusionController();
primaryStage.setTitle("ColorMatrix Extrusion");
FXMLLoader loader = new FXMLLoader();
loader.setLocation(getClass().getResource("ExtrusionForm.fxml"));
try {
extrusionForm = loader.load();
extrusionController = loader.getController();
extCon.setStartValues();
} catch (IOException e) {
e.printStackTrace();
}
Scene scene = new Scene(extrusionForm);
primaryStage.setScene(scene);
primaryStage.show();
}
public static void main(String[] args) {
Application.launch(args);
}
}
Thanks James. Here's the Class with extCon commented out and replaced in with extrusionController.setStartValues() which is still giving a null pointer exception. However if I run the original code I posted but comment out the three setText statements in the ExtrusionController class I no longer get the null pointer exception and the code seems to run ok, obviously not populating the TextFields however.
package extrusion;
import java.io.IOException;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.layout.AnchorPane;
import javafx.stage.Stage;
public class ExtrusionApp extends Application {
private AnchorPane extrusionForm;
private ExtrusionController extrusionController;
public void start(Stage primaryStage) {
//ExtrusionController extCon = new ExtrusionController();
primaryStage.setTitle("ColorMatrix Extrusion");
FXMLLoader loader = new FXMLLoader();
loader.setLocation(getClass().getResource("ExtrusionForm.fxml"));
try {
extrusionForm = loader.load();
extrusionController = loader.getController();
extrusionController.setStartValues();
} catch (IOException e) {
e.printStackTrace();
}
Scene scene = new Scene(extrusionForm);
primaryStage.setScene(scene);
primaryStage.show();
}
public static void main(String[] args) {
Application.launch(args);
}
}
Exception in Application start method
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:498)
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(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.RuntimeException: Exception in Application start method
at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$155(LauncherImpl.java:182)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NullPointerException
at extrusion.ExtrusionApp.start(ExtrusionApp.java:23)
at com.sun.javafx.application.LauncherImpl.lambda$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
Exception running application extrusion.ExtrusionApp
I'm new to Java and I'm really struggling with a null pointer exception to a TextField. I'm trying to populate the TextFields so when the app opens there is already some data in the fields. I know that I'm pointing to the correct method in the ExtrusionController, as I have tried a System.out.println command in the method and it displays ok. I think the problem might be with the references to the TextFields. I've read dozens of forum posts over the last couple of days but I'm going round in circles.
package extrusion;
import java.io.IOException;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.layout.AnchorPane;
import javafx.stage.Stage;
public class ExtrusionApp extends Application {
private AnchorPane extrusionForm;
private ExtrusionController extrusionController;
public void start(Stage primaryStage) {
ExtrusionController extCon = new ExtrusionController();
primaryStage.setTitle("ColorMatrix Extrusion");
FXMLLoader loader = new FXMLLoader();
loader.setLocation(getClass().getResource("ExtrusionForm.fxml"));
try {
extrusionForm = loader.load();
extrusionController = loader.getController();
extCon.setStartValues();
} catch (IOException e) {
e.printStackTrace();
}
Scene scene = new Scene(extrusionForm);
primaryStage.setScene(scene);
primaryStage.show();
}
public static void main(String[] args) {
Application.launch(args);
}
}
package extrusion;
//import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.Button;
import javafx.scene.control.TextField;
public class ExtrusionController {
private double weight = 16.0;
private double rpm = 30.0;
private double time = 0.5;
#FXML
private TextField timeSecs;
#FXML
private TextField revsPerMin;
#FXML
private TextField sampleWeight;
// #FXML
// void 838383(ActionEvent event) {
//
// }
#FXML
public void setStartValues(){
System.out.println();
sampleWeight.setText("" + weight);
revsPerMin.setText("" + rpm);
timeSecs.setText("" + time);
}
}

extCon and extrusionController contain 2 different controller instances. extrusionController is used when loading the fxml and objects from the fxml are injected to this instance.
However you call the setStartValues method for the extCon instance that is not used with a fxml and therefore contains null values in fields.

JavaFX thread issues

I really do my best to not ask for help here unless i am desperate to the point of school assignment failure, being a new coder. That being said, i have spent the last 3 days trying to figure out the issue with threading. I am trying to instantiate a javafx class thats in a separate package, and keep running into the dreaded "java.lang.IllegalStateException: This operation is permitted on the event thread only; currentThread = main" exception.
I have tried calling theGamePreBoard.start(new Stage()), which doesnt work, and i have also tried calling its start method during construction of that object with a new Stage() passed in during construction. Please help!!!
How can i instantiate this PreBoard() class and get it's start method to run without throwing this?
main class:
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package battleship.model;
import battleship.viewcon.*;
import javafx.stage.Stage;
/**
*
* #author foolishklown
*/
public class MainApp {
Player player1;
Player player2;
Board board1;
Board board2;
BattleshipGame theGame;
PreBoard theGamePreBoard;
public void go() {
theGame = new BattleshipGame();
theGamePreBoard = new PreBoard();
theGamePreBoard.start(new Stage());
System.out.println(theGamePreBoard);
theGamePreBoard.setBattleshipGame(theGame);
}
public static void main(String[] args) {
MainApp app = new MainApp();
app.go();
}
}
PreBoard class:
/*
* PreBoard object. This is the starter class for the different JavaFX stages (different windows - username screen,
* and each players window)
* After first username input, this class hides and calls on a new P1Board object
*/
package battleship.viewcon;
import battleship.model.*;
import javafx.geometry.Insets;
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.GridPane;
import javafx.scene.text.Text;
import javafx.stage.Stage;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.layout.HBox;
/**
*
*
* #author c-dub
*/
public class PreBoard extends Application {
private boolean turn; // field to determine which players name to put into which board
private String player;
private Button hideBtn;
private Button showBtn;
private TextField userText;
private ViewCon controller;
private P1Board p1B;
private P2Board p2B;
private BattleshipGame game;
private Stage theStage;
#Override
public void start(Stage primaryStage) {
turn = false;
p1B = new P1Board();
p2B = new P2Board();
controller = new ViewCon();
controller.setp1(p1B);
controller.setp2(p2B);
controller.setPreB(this);
this.game = controller.getBattleshipGame();
primaryStage.setTitle("Battleship setup"); //Main stage (window container)
//Gridpane for using rows/columns for child node placement
GridPane grid = new GridPane();
grid.setAlignment(Pos.CENTER_LEFT);
grid.setHgap(10);
grid.setVgap(5);
grid.setPadding(new Insets(100, 25, 25, 25));
// label in window
Text sceneTitle = new Text("Setup");
sceneTitle.setId("setup-text");
grid.add(sceneTitle, 0, 0, 2, 1);
// label and textfield
Label userName = new Label("Enter UserName:");
userName.setId("user-name");
grid.add(userName, 0, 1);
TextField userTextField = new TextField();
userTextField.setId("text-field");
grid.add(userTextField, 0, 2);
// button for setup, with actionListener to save player name or default if its left blank
Button setupBtn = new Button("Setup Board");
HBox hbBtn = new HBox(10);
hbBtn.setAlignment(Pos.BOTTOM_LEFT);
hbBtn.getChildren().add(setupBtn);
grid.add(hbBtn, 0, 3);
setupBtn.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent e) {
// determine which player name to use to pass into which player board
if(turn == false) {
String temp1 = userTextField.getText();
if(temp1.equals("")) {
player = "Player1";
} else {
player = temp1;
}
controller.setPlayer1(player);
game.setPlayer1(player);
turn = true;
Stage stage = new Stage();
p1B.start(stage);
grid.getChildren().remove(userTextField);
userText = new TextField();
userText.setId("text-field2");
grid.add(userText, 0, 2);
hideBtn.fire();
} else {
String temp2 = userText.getText();
if(temp2.equals("")) {
player = "Player2";
} else {
player = temp2;
}
controller.setPlayer2(player);
game.setPlayer2(player);
Stage stage2 = new Stage();
p2B.start(stage2);
hideBtn.fire();
}
}
});
hideBtn = new Button();
hideBtn.setId("hideBtn");
hideBtn.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent e) {
primaryStage.hide();
}
});
showBtn = new Button();
showBtn.setId("showBtn");
showBtn.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent e) {
primaryStage.show();
}
});
controller.setPreShowBtn(showBtn);
controller.setPreHideBtn(hideBtn);
// Add the entire scene into the main window(stage) after setting the scene dimensions
Scene scene = new Scene(grid, 580, 200);
primaryStage.setScene(scene);
// Attach css stylesheet
scene.getStylesheets().add(PreBoard.class.getResource("styles/PreBoardStyle.css").toExternalForm());
// Show this window(stage) upon instantiation
primaryStage.show();
}
public void setLink(ViewCon v) {
this.controller = v;
}
public static void main(String[] args) {
Application.launch(args);
}
public void setBattleshipGame(BattleshipGame b) {
this.game = b;
}
}

I don't think this has anything at all to do with threading: I don't see any reason why you would ever create another thread in this application. The part you seem to be missing is the actual life-cycle of a JavaFX application. (There's a little you could need to know about how JavaFX manages threading, but it is a bit incidental here.)
The Application class represents an entire application. Your application should typically have just one Application subclass, and one instance of that class. The instance is created for you by JavaFX when you call the static Application.launch() method (or when you execute your Application subclass from the command line, which effectively calls launch for you).
When launch is invoked, the JavaFX toolkit (including the FX Application Thread) is started. An instance of theApplication subclass is created for you, and then start(...) is invoked on that instance on the FX Application Thread.
So what that means is that the start(...) method is the entry point (startup) for your JavaFX application. Since the most common thing to do here is to display something in a window, a window (Stage) is passed into this method for your convenience: however you can ignore it and just create your own if you like.
A typical start(...) method should be quite short, and will usually just create some UI (maybe defined in another class or in an FXML file), put that UI in a scene, and display the scene in a stage. In a more complex application, you will create an instance of your model class here, create some views and controllers, give the controllers references to the model, and assemble the views.
For a simple structural example, see my answer to Java: How do I start a standalone application from the current one when both are in the same package? (which is a similar question, I think).

JavaFX: application Launch Must not be called more than once

I am new to JavaFX and I was just typing some code...but whenever I try to run the application the second time I get an error stating: application launch must not be called more than once:
My first code was:
import javafx.application.Application;
import javafx.stage.Stage;
import javafx.application.*;
public class App extends Application{
public void start (Stage primaryStage){
primaryStage.setTitle("Chess");
primaryStage.show();
}
public static void main(String args[]){
Application.launch (args);
}
}
then after doing some search I changed it to:
import javafx.application.Application;
import javafx.stage.Stage;
import javafx.application.*;
public class App extends Application{
public void start (Stage primaryStage){
Platform.setImplicitExit(true);
primaryStage.setTitle("Chess");
primaryStage.show();
}
public static void main(String args[]){
Application.launch (args);
}
}
But it still shows the same error:
java.lang.IllegalStateException: Application launch must not be called more than once

Why you are adding
Platform.setImplicitExit(true);
it is by default true, you don't need to call main method, just compile and run your application.

Mixing Swing/FX: can't dispose a dialog from fxml controller

The scenario: the top-level container is a Swing JDialog which has some fx content, including a fx button that triggers a dispose of the button. Disposing works a expected (dialog is hidden) when the button is created and configured with the appropriate eventHandler manually. The dialog is not disposed when the button is created/configure via fxml. The example below contains both a manually configured and a fxml loaded/bound button to see the different behaviour.
Questions:
anything wrong with the example?
is there any difference in swing/fx interaction to be expected (manual vs. fxml)?
how to make it work from fxml?
The code:
package fxml;
import java.io.IOException;
import javafx.application.Platform;
import javafx.embed.swing.JFXPanel;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.FlowPane;
import javax.swing.JDialog;
import javax.swing.SwingUtilities;
public class DisposeExample {
#FXML
Button closeButton;
Button fxButton;
private JDialog dialog;
/**
* The action handler method used by fx buttons.
*/
public void onAction(final ActionEvent ac) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
System.out.println("onAction: " +ac);
dialog.dispose();
}
});
}
protected Button createFxButton() {
Button fxButton = new Button("close from fx");
fxButton.setOnAction(new javafx.event.EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent event) {
onAction(event);
}
});
return fxButton;
}
public void initFX() {
final JFXPanel fxPanel = new JFXPanel();
dialog.add(fxPanel);
Platform.runLater(new Runnable() {
#Override
public void run() {
FlowPane parent = null;
try {
parent = FXMLLoader.load(DisposeExample.class.getResource(
"DisposeController.fxml"));
} catch (IOException e) {
e.printStackTrace();
}
fxButton = createFxButton();
parent.getChildren().add(fxButton);
Scene scene = new Scene(parent);
fxPanel.setScene(scene);
}
});
}
public DisposeExample() {
dialog = new JDialog();
dialog.setTitle("Simple Swing Dialog");
initFX();
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
JDialog example = new DisposeExample().dialog;
example.setSize(400, 400);
example.setVisible(true);
}
});
}
}
The fxml content:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<FlowPane id="Content" fx:id="windowPanel"
xmlns:fx="http://javafx.com/fxml" fx:controller="fxml.DisposeExample">
<children>
<Button fx:id="closeButton" onAction="#onAction"
prefHeight="35.0" prefWidth="300.0" text="Close (fxml controller)">
</Button>
</children>
</FlowPane>
BTW: there's a similar question from the beginning of this year, unanswered.
Edit
something weird going on: after running for a couple of minutes, it throws a OutOfMemoryError - something deeper down doesn't stop creating .. what?
java.lang.OutOfMemoryError: Java heap space
at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Class.java:2521)
at java.lang.Class.privateGetPublicMethods(Class.java:2641)
at java.lang.Class.privateGetPublicMethods(Class.java:2657)
at java.lang.Class.privateGetPublicMethods(Class.java:2657)
at java.lang.Class.privateGetPublicMethods(Class.java:2657)
at java.lang.Class.privateGetPublicMethods(Class.java:2657)
at java.lang.Class.privateGetPublicMethods(Class.java:2657)
at java.lang.Class.getMethods(Class.java:1457)
at sun.reflect.misc.MethodUtil.getMethods(MethodUtil.java:99)
at com.sun.javafx.fxml.BeanAdapter.updateMethodCache(BeanAdapter.java:265)
at com.sun.javafx.fxml.BeanAdapter.setBean(BeanAdapter.java:250)
at com.sun.javafx.fxml.BeanAdapter.<init>(BeanAdapter.java:213)
at javafx.fxml.FXMLLoader$Element.getValueAdapter(FXMLLoader.java:157)
at javafx.fxml.FXMLLoader$Element.getProperties(FXMLLoader.java:165)
at javafx.fxml.FXMLLoader$ValueElement.processValue(FXMLLoader.java:647)
at javafx.fxml.FXMLLoader$ValueElement.processStartElement(FXMLLoader.java:570)
at javafx.fxml.FXMLLoader.processStartElement(FXMLLoader.java:2314)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2131)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2028)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2744)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2723)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2709)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2696)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2685)
at fxml.DisposeExample$3.run(DisposeExample.java:65)
at com.sun.javafx.application.PlatformImpl$4$1.run(PlatformImpl.java:179)
at com.sun.javafx.application.PlatformImpl$4$1.run(PlatformImpl.java:176)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl$4.run(PlatformImpl.java:176)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.access$100(WinApplication.java:29)
Edit
fyi: same behaviour in 8u113, so filed an issue in fx-jira, incurable optimist that I am :-)

anything wrong with the example?
a resounding YES - citing Martin's (very quick and clear :-) comment to the issue:
The problem is in your fxml file.
"fx:controller" attribute takes the class and creates a new instance
of it (using the default contructor). The default constructor of your
DisposeExample class posts a new Runnable that will load the same fxml
file again a create yet another instance of DisposeExample class.
You should either use a different class for your controller or set the
controller manually using the setController() call or using a
controller factory (setControllerFactory). Otherwise, there is no way
for FXMLLoader to know that you wanted to use your particular
DisposeExample object.

Bug alert - remove the controller from the FXML-file and set it in the code instead.
FXMLLoader fxmlLoader = new FXMLLoader(DisposeExample.class.getResource("DisposeController.fxml"));
fxmlLoader.setController(DisposeExample.this);
parent = (FlowPane)fxmlLoader.load();
Unfortunately this will also destroy the FX-CPU-heating on these cold days ;-)

So why are you not executing the dispose on the swing thread?