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“javafx.fxml.LoadException” error when loading fxml - java

For a project I need to create a GUI using JavaFX. So with a tutorial of Scene Builder/JavaFX that I followed very closely I created a very basic GUI. But the load doesn't seem to work and throws an LoadException. I've seem a few similar problems online, but none of their answers seemed to fix mine. I have done as much googleFoo as I can trying similar guides and tutorials, but it just won't load.
Here is main:
package stacksim;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;
public class stacksim extends Application {
public static void main(String[] args) {
launch(args);
}
#Override
public void start(Stage primaryStage) throws Exception {
try {
// Read file fxml and draw interface.
Parent root = FXMLLoader.load(getClass()
.getResource("stacksim.fxml"));
primaryStage.setTitle("Stack Simulation");
primaryStage.setScene(new Scene(root));
primaryStage.show();
} catch(Exception e) {
e.printStackTrace();
}
}
}
Controller:
package stacksim;
import java.net.URL;
import java.util.ResourceBundle;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.geometry.Pos;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.layout.GridPane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.scene.transform.Translate;
/**
* FXML Controller class
*
* #author Dell
*/
public class stacksimcontroller implements Initializable {
#FXML
private Button btnPush;
#FXML
private Button btnPop;
#FXML
private Button btnExit;
#FXML
private GridPane gridBoxBall;
#FXML
private GridPane gridBoxNum;
#FXML
private Label description;
private int curColumn = 0;
private int count = 0;
#Override
public void initialize(URL url, ResourceBundle rb) {
// TODO
}
public void actionPush(ActionEvent event) {
System.out.println("Button Push Clicked!");
if (curColumn >= 10) {
description.setText("Stack is fully, you can't push more !");
} else {
addCircle(curColumn, 0);
addLabel(curColumn, 0);
System.out.println(' ');
count++;
description.setText("Push successfully!");
curColumn++;
System.out.println(curColumn);
}
}
public void actionPop(ActionEvent event) {
System.out.println("Button Pop Clicked!");
if (curColumn == 0) {
description.setText("Stack Empty! Nothing to pop!");
System.out.println(curColumn);
} else if (curColumn == 1) {
curColumn--;
gridBoxBall.getChildren().remove(curColumn);
gridBoxNum.getChildren().remove(curColumn);
description.setText("Pop successfully!");
System.out.println(curColumn);
} else {
curColumn--;
gridBoxBall.getChildren().remove(curColumn);
gridBoxNum.getChildren().remove(curColumn);
System.out.println(curColumn);
for (int i = 0; i < curColumn; i++) {
Translate translate = new Translate();
translate.setZ(0);
translate.setY(0);
translate.setX(0);
gridBoxBall.getChildren().get(i).getTransforms().addAll(translate);
gridBoxNum.getChildren().get(i).getTransforms().addAll(translate);
}
description.setText("Pop successfully!");
}
}
public void actionExit(ActionEvent event) {
System.exit(0);
}
public void addCircle(int col, int row){
Circle circle = new Circle(20);
circle.setFill(Color.FIREBRICK);
gridBoxBall.add(circle, col, row);
}
public void addLabel(int col, int row){
Label label = new Label(count + "");
label.setPrefSize(40, 40);
label.setAlignment(Pos.CENTER);
gridBoxNum.add(label, col, row);
}
}
fxml:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.text.*?>
<?import javafx.scene.shape.*?>
<?import javafx.geometry.*?>
<?import java.lang.*?>
<?import java.net.*?>
<?import java.util.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<AnchorPane 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="queuedemon.QueueDemonController">
<children>
<Label alignment="CENTER" contentDisplay="CENTER" layoutX="-4.0" layoutY="-3.0" prefHeight="65.0" prefWidth="606.0" text="STACK HAVING 10 SLOTS" textFill="FIREBRICK">
<font>
<Font name="Arial Bold" size="26.0" />
</font>
</Label>
<HBox alignment="CENTER" layoutX="1.0" layoutY="335.0" prefHeight="51.0" prefWidth="600.0" spacing="100.0">
<children>
<Button fx:id="btnPush" alignment="CENTER" mnemonicParsing="false" onAction="#actionPush" text="PUSH" textFill="FIREBRICK" />
<Button fx:id="btnPop" alignment="CENTER" mnemonicParsing="false" onAction="#actionPop" text="POP" textFill="FIREBRICK" />
</children>
<opaqueInsets>
<Insets />
</opaqueInsets>
<padding>
<Insets bottom="20.0" left="20.0" right="20.0" top="20.0" />
</padding>
</HBox>
<Label fx:id="description" alignment="CENTER" layoutX="2.0" layoutY="281.0" prefHeight="17.0" prefWidth="600.0" textFill="FIREBRICK">
<font>
<Font size="14.0" />
</font>
</Label>
<GridPane fx:id="gridBoxBall" hgap="10.0" layoutX="62.0" layoutY="180.0" prefHeight="40.0" prefWidth="500.0" AnchorPane.bottomAnchor="180.0" AnchorPane.leftAnchor="62.0" AnchorPane.rightAnchor="38.0" AnchorPane.topAnchor="180.0">
<columnConstraints>
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
</columnConstraints>
<rowConstraints>
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
</rowConstraints>
<padding>
<Insets left="10.0" right="10.0" />
</padding>
</GridPane>
<GridPane fx:id="gridBoxNum" hgap="10.0" layoutX="62.0" layoutY="241.0" prefHeight="40.0" prefWidth="500.0">
<columnConstraints>
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
</columnConstraints>
<rowConstraints>
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
</rowConstraints>
<padding>
<Insets left="10.0" right="10.0" />
</padding>
</GridPane>
<Button fx:id="btnExit" alignment="CENTER" layoutX="537.0" layoutY="14.0" mnemonicParsing="false" onAction="#actionExit" text="EXIT" textFill="FIREBRICK" />
</children>
</AnchorPane>
error:
javafx.fxml.LoadException:
/E:/Study/OOP/Java/JavaMidterm/TestQueueMidterm/bin/stacksim/stacksim.fxml
at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2601)
at javafx.fxml.FXMLLoader.importClass(FXMLLoader.java:2848)
at javafx.fxml.FXMLLoader.processImport(FXMLLoader.java:2692)
at javafx.fxml.FXMLLoader.processProcessingInstruction(FXMLLoader.java:2661)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2517)
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 stacksim.stacksim.start(stacksim.java:31)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$161(LauncherImpl.java:863)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$174(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl.lambda$null$172(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$173(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$147(WinApplication.java:177)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.ClassNotFoundException
at javafx.fxml.FXMLLoader.loadType(FXMLLoader.java:2899)
at javafx.fxml.FXMLLoader.importClass(FXMLLoader.java:2846)
... 20 more

Related

I have a vbox which contains a list of cards(Anchor panes). I am trying to make each card draggable so that I can change the order of the list whenever I want. I am using a scene builder.
However, I keep getting the following message after I drag and attempt to drop.
Java Messsge:class javafx.scene.layout.VBox cannot be cast to class javafx.scene.layout.AnchorPane(javafx.scene.layout.VBox and javafx.scene.layout.AnchorPane are in module javafx.graphics of loader 'app')
My code:
minimal code provided only contains two cards, one of which is being used only in my code.
Edit: I no longer get the error message however, I am not getting my desired result as the cards are not changing positions
mport javafx.beans.property.ObjectProperty;
import javafx.event.EventHandler;
import javafx.fxml.FXML;
import javafx.scene.Node;
import javafx.scene.Parent;
import javafx.scene.SnapshotParameters;
import javafx.scene.control.Button;
import javafx.scene.control.ScrollPane;
import javafx.scene.control.TitledPane;
import javafx.scene.image.WritableImage;
import javafx.scene.input.*;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.VBox;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class Controller
{
#FXML public AnchorPane card1, card2;
#FXML public AnchorPane current;
#FXML public GridPane gridPane;
#FXML public GridPane column1;
#FXML public AnchorPane col1;
#FXML public Button button1, button2;
#FXML public Button currentButton;
#FXML public VBox v1;
#FXML
public void detect() { //detect card
card1.setOnDragDetected((MouseEvent event) -> { //card1 is the card
Dragboard db = card1.startDragAndDrop(TransferMode.MOVE);
ClipboardContent content = new ClipboardContent();
content.putString(card1.getId());
WritableImage snapshot = card1.snapshot(new SnapshotParameters(), null);
db.setDragView(snapshot);
db.setContent(content);
event.consume();
});
}
#FXML
public void accept() { //add to vbox
v1.addEventHandler(DragEvent.DRAG_OVER, (DragEvent event) -> { //v1 is the vbox
if (event.getGestureSource() != v1
&& event.getDragboard().hasString()) {
event.acceptTransferModes(TransferMode.COPY_OR_MOVE);
}
event.consume();
});
}
#FXML
public void drop() {
v1.addEventHandler(DragEvent.DRAG_DROPPED, (DragEvent event) -> {
Dragboard db = event.getDragboard();
boolean success = false;
if (db.hasString()) {
VBox parent = (VBox) card1.getParent();
//int targetIndex = parent.getChildren().indexOf(card1);
List<Node> nodes = new ArrayList<Node>(parent.getChildren());
parent.getChildren().clear();
parent.getChildren().addAll(nodes);
success = true;
}
event.setDropCompleted(success);
event.consume();
});
}
}
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.TextArea?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.layout.ColumnConstraints?>
<?import javafx.scene.layout.GridPane?>
<?import javafx.scene.layout.Pane?>
<?import javafx.scene.layout.RowConstraints?>
<?import javafx.scene.layout.VBox?>
<?import javafx.scene.text.Font?>
<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="772.0" prefWidth="1295.0" style="-fx-background-color: #C5F5D4;" xmlns="http://javafx.com/javafx/11.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="KanbanBoard.Controller">
<children>
<AnchorPane layoutY="47.0" prefHeight="687.0" prefWidth="1295.0">
<children>
<AnchorPane fx:id="col1" layoutX="-1.0" prefHeight="724.0" prefWidth="216.0">
<children>
<GridPane fx:id="column1" layoutX="33.0" layoutY="15.0" onMouseDragOver="#accept" prefHeight="724.0" prefWidth="209.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="7.0" AnchorPane.topAnchor="0.0">
<columnConstraints>
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
</columnConstraints>
<rowConstraints>
<RowConstraints maxHeight="353.8666748046875" minHeight="10.0" prefHeight="103.20001831054685" vgrow="SOMETIMES" />
<RowConstraints maxHeight="621.5999816894531" minHeight="10.0" prefHeight="621.5999816894531" vgrow="SOMETIMES" />
</rowConstraints>
<children>
<VBox fx:id="v1" onDragDropped="#drop" onDragOver="#accept" prefHeight="200.0" prefWidth="210.0" GridPane.rowIndex="1">
<children>
<AnchorPane fx:id="card1" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" onDragDetected="#detect" onMouseDragged="#handleLabel" prefHeight="125.0" prefWidth="198.0" style="-fx-background-color: #E5EAE6;">
<children>
<TextField layoutX="5.0" layoutY="3.0" prefHeight="26.0" prefWidth="65.0" promptText="ID" />
<TextField layoutX="72.0" layoutY="3.0" prefHeight="26.0" prefWidth="124.0" promptText="Title" />
<TextArea layoutX="5.0" layoutY="32.0" prefHeight="50.0" prefWidth="190.0" promptText="Description" />
<TextField layoutX="5.0" layoutY="85.0" prefHeight="26.0" prefWidth="124.0" promptText="Story point" />
<Button fx:id="button1" layoutX="164.0" layoutY="85.0" mnemonicParsing="false" onMouseClicked="#removeCard" prefHeight="24.0" prefWidth="31.0" style="-fx-background-color: #ECF4EE;" text="-" />
<Button layoutX="129.0" layoutY="85.0" mnemonicParsing="false" prefHeight="24.0" prefWidth="31.0" style="-fx-background-color: #ECF4EE;" text="+" />
</children>
</AnchorPane>
<AnchorPane fx:id="card2" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" onDragDetected="#detect" onMouseClicked="#handleLabel" prefHeight="125.0" prefWidth="198.0" style="-fx-background-color: #E5EAE6;">
<children>
<TextField layoutX="5.0" layoutY="3.0" prefHeight="26.0" prefWidth="65.0" promptText="ID" />
<TextField layoutX="72.0" layoutY="3.0" prefHeight="26.0" prefWidth="124.0" promptText="Title" />
<TextArea layoutX="5.0" layoutY="32.0" prefHeight="50.0" prefWidth="190.0" promptText="Description" />
<TextField layoutX="5.0" layoutY="85.0" prefHeight="26.0" prefWidth="124.0" promptText="Story point" />
<Button fx:id="button2" layoutX="164.0" layoutY="85.0" mnemonicParsing="false" onMouseClicked="#removeCard" prefHeight="24.0" prefWidth="31.0" style="-fx-background-color: #ECF4EE;" text="-" />
<Button layoutX="129.0" layoutY="85.0" mnemonicParsing="false" prefHeight="24.0" prefWidth="31.0" style="-fx-background-color: #ECF4EE;" text="+" />
</children>
</AnchorPane>
</children>
</VBox>
<Pane prefHeight="98.0" prefWidth="226.0" style="-fx-background-color: #D1D3D1;">
<children>
<Button layoutX="124.0" layoutY="64.0" mnemonicParsing="false" prefHeight="26.0" prefWidth="26.0" text="-" />
<TextArea layoutY="39.0" prefHeight="50.0" prefWidth="124.0" promptText="Role" />
<TextField layoutX="1.0" layoutY="5.0" prefHeight="26.0" prefWidth="124.0" promptText="Name" />
<Button fx:id="addColumnButton" layoutX="124.0" layoutY="36.0" mnemonicParsing="false" prefHeight="26.0" prefWidth="26.0" text="+" />
</children>
</Pane>
</children>
</GridPane>
</children>
</AnchorPane>
<AnchorPane layoutX="1082.0" prefHeight="726.0" prefWidth="213.0">
<children>
<Pane prefHeight="50.0" prefWidth="214.0" style="-fx-background-color: #8F9691;">
<children>
<Label layoutX="49.0" layoutY="7.0" prefHeight="36.0" prefWidth="46.0" text="Log" textAlignment="CENTER" textOverrun="WORD_ELLIPSIS">
<font>
<Font size="22.0" />
</font>
</Label>
</children>
</Pane>
<Pane layoutY="49.0" prefHeight="676.0" prefWidth="214.0" style="-fx-background-color: #C6C8C6;" />
</children>
</AnchorPane>
<GridPane fx:id="gridPane" layoutX="228.0" onDragDropped="#drop" onDragOver="#accept" prefHeight="726.0" prefWidth="856.0">
<columnConstraints>
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
</columnConstraints>
<rowConstraints>
<RowConstraints maxHeight="627.1999938964843" minHeight="10.0" prefHeight="622.4000061035156" vgrow="SOMETIMES" />
</rowConstraints>
</GridPane>
</children>
</AnchorPane>
<Label layoutX="381.0" layoutY="-4.0" prefHeight="50.0" prefWidth="180.0" text="Kanban Board">
<font>
<Font size="28.0" />
</font>
</Label>
</children>
</AnchorPane>
import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.input.*;
import javafx.stage.Stage;
import java.io.IOException;
public class Kanban extends Application {
//private Button b;
public static void main(String[] args) {
launch(args);
}
#Override
public void start(Stage primaryStage) {
Parent root = null;
try {
root = FXMLLoader.load(getClass().getResource("Kanban.fxml"));
} catch (IOException e) {
throw new RuntimeException(e);
}
Controller controller = new Controller();
FXMLLoader loader = new FXMLLoader();
loader.setController(controller);
//Controller c = loader.getController();
Scene scene = new Scene(root);
primaryStage.setScene(scene);
primaryStage.show();
}
}
Can someone help me out please.

AnchorPane parent = (AnchorPane) card1.getParent(); (In the drop() method, at the bottom of your code)
card1.getParent() with a type of VBox cannot be cast to AnchorPane

i have application layout:
https://i.stack.imgur.com/YsK5R.png
as a result of writing code I get this
https://i.stack.imgur.com/j2Nym.png
Question: How to remove the top line with closing tabs and leave only as on the layout?
project structure:
-[src]
.....|-[sample]
..............|- Main
..............|- sample.fxml
..............|- SampleController
..............|- Tab1.fxml
..............|- Tab1Controller
..............|- Tab2.fxml
..............|- Tab2Controller
CODE
class Main
package sample;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.control.Tab;
import javafx.scene.control.TabPane;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;
import java.io.IOException;
public class Main extends Application {
private Stage primary;
private BorderPane rootLayout;
#Override
public void start(Stage primary) throws Exception{
this.primary = primary;
initRootLayout();
showTab();
}
private void initRootLayout() {
try {
FXMLLoader loader = new FXMLLoader();
loader.setLocation(Main.class.getResource("sample.fxml"));
rootLayout = loader.load();
Scene scene = new Scene(rootLayout);
primary.setScene(scene);
primary.show();
}catch (IOException e){
e.printStackTrace();}
}
private void showTab() {
try {
FXMLLoader loaderTab1 = new FXMLLoader();
loaderTab1.setLocation(Main.class.getResource("Tab1.fxml"));
FXMLLoader loaderTab2 = new FXMLLoader();
loaderTab2.setLocation(Main.class.getResource("Tab2.fxml"));
TabPane tabPane = new TabPane();
Tab tab1 = new Tab();
Tab tab2 = new Tab();
tab1.setContent(loaderTab1.load());
tab2.setContent(loaderTab2.load());
tabPane.getTabs().addAll(tab1,tab2);
rootLayout.setCenter(tabPane);
} catch (IOException e){
e.printStackTrace();
}
}
public static void main(String[] args) {
launch(args);
}
}
sample.fxml
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Menu?>
<?import javafx.scene.control.MenuBar?>
<?import javafx.scene.control.MenuItem?>
<?import javafx.scene.layout.BorderPane?>
<BorderPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.172-ea" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.SampleController">
<top>
<MenuBar BorderPane.alignment="CENTER">
<menus>
<Menu mnemonicParsing="false" text="File">
<items>
<MenuItem mnemonicParsing="false" text="Close" />
</items>
</Menu>
<Menu mnemonicParsing="false" text="Edit">
<items>
<MenuItem mnemonicParsing="false" text="Delete" />
</items>
</Menu>
<Menu mnemonicParsing="false" text="Help">
<items>
<MenuItem mnemonicParsing="false" text="About" />
</items>
</Menu>
</menus>
</MenuBar>
</top>
</BorderPane>
Tab1.fxml = Tab2.fxml = ... = Tab{n}.fxml
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.SplitPane?>
<?import javafx.scene.control.Tab?>
<?import javafx.scene.control.TabPane?>
<?import javafx.scene.control.TableColumn?>
<?import javafx.scene.control.TableView?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.layout.ColumnConstraints?>
<?import javafx.scene.layout.GridPane?>
<?import javafx.scene.layout.RowConstraints?>
<TabPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" tabClosingPolicy="UNAVAILABLE" xmlns="http://javafx.com/javafx/10.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Tab1Controller">
<tabs>
<Tab text="Tab1">
<content>
<SplitPane dividerPositions="0.29797979797979796" prefHeight="160.0" prefWidth="200.0">
<items>
<AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="160.0" prefWidth="100.0">
<children>
<TableView fixedCellSize="1.0" layoutX="-12.0" layoutY="27.0" prefHeight="371.0" prefWidth="176.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
<columns>
<TableColumn prefWidth="75.0" text="C1" />
<TableColumn prefWidth="75.0" text="C2" />
</columns>
<columnResizePolicy>
<TableView fx:constant="CONSTRAINED_RESIZE_POLICY" />
</columnResizePolicy>
</TableView>
</children></AnchorPane>
<AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="160.0" prefWidth="100.0">
<children>
<Label layoutY="14.0" text="Label" AnchorPane.leftAnchor="5.0" AnchorPane.topAnchor="14.0" />
<GridPane layoutX="98.0" layoutY="125.0" AnchorPane.leftAnchor="5.0" AnchorPane.rightAnchor="5.0" AnchorPane.topAnchor="35.0">
<columnConstraints>
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
</columnConstraints>
<rowConstraints>
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
</rowConstraints>
<children>
<Label text="Label" />
<Label text="Label" GridPane.rowIndex="1" />
<Label text="Label" GridPane.rowIndex="2" />
<Label text="Label" GridPane.columnIndex="1" />
<Label text="Label" GridPane.columnIndex="1" GridPane.rowIndex="1" />
<Label text="Label" GridPane.columnIndex="1" GridPane.rowIndex="2" />
</children>
</GridPane>
</children></AnchorPane>
</items>
</SplitPane>
</content></Tab>
</tabs>
</TabPane>
this question is double from this: https://ru.stackoverflow.com/questions/941060/%D0%A3%D0%B1%D1%80%D0%B0%D1%82%D1%8C-%D0%B2%D1%82%D0%BE%D1%80%D0%B8%D1%87%D0%BD%D1%8B%D0%B5-%D0%B2%D0%BA%D0%BB%D0%B0%D0%B4%D0%BA%D0%B8

There are many way to do this depending on the genericity you want to add to your application/layout.
But the most important thing is that you seem to make a mistake by mixing up the TabPane and the Tabs. While the first one is the container, the second(s) one(s) correspond to each tab you could have. Usually you have one TabPane which contain many Tab(s) (even if it is not necessary).
One solution could be to modify your method showTab by doing this (read comment)
private void showTab() {
try {
// Tab 1 loader
FXMLLoader loaderTab1 = new FXMLLoader(Main.class.getResource("Tab1.fxml"));
// Tab 2 loader
FXMLLoader loaderTab2 = new FXMLLoader(Main.class.getResource("Tab2.fxml"));
TabPane tabPane = new TabPane();
// Remove the 4 following lines, Tabs are already declared in FXML
//Tab tab1 = new Tab();
//Tab tab2 = new Tab();
//tab1.setContent(loaderTab1.load());
//tab2.setContent(loaderTab2.load());
Tab tab1 = loaderTab1.load();
Tab tab2 = loaderTab2.load();
tabPane.getTabs().addAll(tab1,tab2);
rootLayout.setCenter(tabPane);
} catch (IOException e){
e.printStackTrace();
}
}
And change your FXML files like the following one (TabPane and tabs tags are removed) :
<Tab xmlns="http://javafx.com/javafx/10.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Tab1Controller" text="Tab1">
<content>
<SplitPane dividerPositions="0.29797979797979796" prefHeight="160.0" prefWidth="200.0">
<items>
<AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="160.0" prefWidth="100.0">
<children>
<TableView fixedCellSize="1.0" layoutX="-12.0" layoutY="27.0" prefHeight="371.0" prefWidth="176.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
<columns>
<TableColumn prefWidth="75.0" text="C1" />
<TableColumn prefWidth="75.0" text="C2" />
</columns>
<columnResizePolicy>
<TableView fx:constant="CONSTRAINED_RESIZE_POLICY" />
</columnResizePolicy>
</TableView>
</children></AnchorPane>
<AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="160.0" prefWidth="100.0">
<children>
<Label layoutY="14.0" text="Label" AnchorPane.leftAnchor="5.0" AnchorPane.topAnchor="14.0" />
<GridPane layoutX="98.0" layoutY="125.0" AnchorPane.leftAnchor="5.0" AnchorPane.rightAnchor="5.0" AnchorPane.topAnchor="35.0">
<columnConstraints>
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
</columnConstraints>
<rowConstraints>
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
</rowConstraints>
<children>
<Label text="Label" />
<Label text="Label" GridPane.rowIndex="1" />
<Label text="Label" GridPane.rowIndex="2" />
<Label text="Label" GridPane.columnIndex="1" />
<Label text="Label" GridPane.columnIndex="1" GridPane.rowIndex="1" />
<Label text="Label" GridPane.columnIndex="1" GridPane.rowIndex="2" />
</children>
</GridPane>
</children></AnchorPane>
</items>
</SplitPane>
</content>
</Tab>

In my JavaFX program I have multiple grid panes. The FXML code I have is here.
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.shape.*?>
<?import javafx.geometry.*?>
<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<AnchorPane id="AnchorPane" prefHeight="553.0" prefWidth="586.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="pkg3dtictactoe.FXMLDocumentController">
<children>
<VBox prefHeight="489.0" prefWidth="586.0">
<children>
<MenuBar>
<menus>
<Menu mnemonicParsing="false" text="File">
<items>
<MenuItem id="NewGame" mnemonicParsing="false" onAction="#handleNewGameAction" text="New Game" />
<MenuItem id="SaveGame" mnemonicParsing="false" onAction="#handleSaveGameAction" text="Save Game" />
<MenuItem id="Quit" mnemonicParsing="false" onAction="#handleQuitGameAction" text="Quit" />
</items>
</Menu>
<Menu mnemonicParsing="false" text="Help">
<items>
<MenuItem mnemonicParsing="false" text="About" />
</items>
</Menu>
</menus>
</MenuBar>
<GridPane fx:id="topGrid" alignment="CENTER" gridLinesVisible="true" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" onMouseClicked="#topGridClicked" prefHeight="175.0" prefWidth="175.0" rotate="-73.0" style="-fx-background-color: #FFFFFF;" VBox.vgrow="NEVER">
<columnConstraints>
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
</columnConstraints>
<rowConstraints>
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
</rowConstraints>
<rotationAxis>
<Point3D x="1.0" y="1.0" z="1.0" />
</rotationAxis>
<VBox.margin>
<Insets left="200.0" top="50.0" />
</VBox.margin>
</GridPane>
<GridPane fx:id="middleGrid" gridLinesVisible="true" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" onMouseClicked="#middleGridClicked" prefHeight="175.0" prefWidth="175.0" rotate="-73.0" style="-fx-background-color: #FFFFFF;" VBox.vgrow="NEVER">
<columnConstraints>
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
</columnConstraints>
<rowConstraints>
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
</rowConstraints>
<rotationAxis>
<Point3D x="1.0" y="1.0" z="1.0" />
</rotationAxis>
<VBox.margin>
<Insets left="200.0" top="-45.0" />
</VBox.margin>
</GridPane>
<GridPane fx:id="lowerGrid" gridLinesVisible="true" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" onMouseClicked="#lowerGridClicked" prefHeight="175.0" prefWidth="175.0" rotate="-73.0" style="-fx-background-color: #FFFFFF;" VBox.vgrow="NEVER">
<columnConstraints>
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
</columnConstraints>
<rowConstraints>
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
</rowConstraints>
<rotationAxis>
<Point3D x="1.0" y="1.0" z="1.0" />
</rotationAxis>
<VBox.margin>
<Insets left="200.0" top="-40.0" />
</VBox.margin>
</GridPane>
<Label prefHeight="17.0" prefWidth="588.0" />
</children>
</VBox>
<Line endX="172.0" endY="410.0" startX="172.0" startY="145.0" style="-fx-opacity: .2;" />
<Line endX="403.0" endY="447.0" startX="403.0" startY="182.0" style="-fx-opacity: .2;" />
<Line endX="265.0" endY="353.0" startX="265.0" startY="89.0" style="-fx-opacity: .2;" />
<Line endX="310.0" endY="500.0" startX="310.0" startY="235.0" style="-fx-opacity: .2;" />
</children>
</AnchorPane>
The FXML Controller code is the following
package pkg3dtictactoe;
import java.io.IOException;
import java.net.URL;
import java.util.Iterator;
import java.util.ResourceBundle;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.Node;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.GridPane;
/**
*
*/
public class FXMLDocumentController implements Initializable {
#FXML
private GridPane topGrid;
private GridPane middleGrid;
private GridPane lowerGrid;
private Image imageX = null;
private Image imageO = null;
private Image imageEmpty = null;
public FXMLDocumentController(){
imageEmpty = new Image("resources/empty.png");
imageX = new Image("resources/x.png");
imageO = new Image("resources/0.png");
}
#FXML
private void handleButtonAction(ActionEvent event) {
}
#FXML
private void handleNewGameAction(ActionEvent event) throws IOException {
for(int i=0; i<3; i++){
for(int j=0; j<3; j++){
resetNode(topGrid, i, j);
resetNode(middleGrid, i, j);
resetNode(lowerGrid, i, j);
}
}
}
private void resetNode(GridPane grid, int i, int j) {
Node node = getNodeByRowColumnIndex(j, i, grid);
grid.getChildren().remove(node);
grid.add(new ImageView(imageEmpty), j, i);
}
public Node getNodeByRowColumnIndex(final int row,final int column,GridPane gridPane) {
Node result = null;
ObservableList<Node> childrens = gridPane.getChildren();
for(Node node : childrens) {
if(node instanceof ImageView && gridPane.getRowIndex(node) == row && gridPane.getColumnIndex(node) == column) {
result = node;
break;
}
}
return result;
}
#Override
public void initialize(URL url, ResourceBundle rb) {
// TODO
}
}
When I run debug into the constructor, topGrid has information, however middleGrid and lowerGrid do not. There doesn't appear to be anything special when it comes to topGrid and it matches the code for the other GridPanes. Is it not possible to have multiple grid panes in JavaFX?

#FXML annotations apply to the Object declared directly after them. You need to write the annotation multiple times on the lines above every component with an fx:id to connect them.

I am trying to run the following very simple app
Main.java:
package sample;
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("sample.fxml"));
primaryStage.setTitle("Hello World");
primaryStage.setScene(new Scene(root, 600, 400));
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}
Controller.java
package sample;
import java.awt.*;
public class Controller {
public TextField theight;
public TextField tweight;
public Label lbmi;
public Label lresult;
public void buttonclicked(){
double height;
double weight;
double bmi;
String result;
height = Double.parseDouble(theight.getText());
weight = Double.parseDouble(tweight.getText());
double square = height * height;
bmi = weight / square;
lbmi.setText("The BMI is " + bmi);
}
}
and sample.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.ColumnConstraints?>
<?import javafx.scene.layout.GridPane?>
<?import javafx.scene.layout.RowConstraints?>
<?import javafx.scene.text.Font?>
<GridPane 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="sample.Controller">
<columnConstraints>
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
</columnConstraints>
<rowConstraints>
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
</rowConstraints>
<children>
<Label alignment="CENTER" prefHeight="43.0" prefWidth="210.0" text="BMI Calculator" GridPane.columnIndex="1">
<font>
<Font size="29.0" />
</font>
</Label>
<TextField fx:id="theight" alignment="CENTER" promptText="Enter your height in meters" GridPane.columnIndex="1" GridPane.rowIndex="1" />
<TextField fx:id="tweight" alignment="CENTER" promptText="Enter your weight in kg" GridPane.columnIndex="1" GridPane.rowIndex="2" />
<Button mnemonicParsing="false" onAction="#buttonclicked" text="Calculate" GridPane.columnIndex="2" GridPane.rowIndex="3" />
<Label fx:id="lbmi" alignment="CENTER" prefHeight="17.0" prefWidth="280.0" text="Your BMI will be displayed here" textOverrun="CLIP" GridPane.columnIndex="1" GridPane.rowIndex="3" />
<Label fx:id="lresult" alignment="CENTER" prefHeight="17.0" prefWidth="211.0" text="What your BMI means" GridPane.columnIndex="1" GridPane.rowIndex="4" />
</children>
</GridPane>
I have figured out that the controller was not added by default and added it as fx:controller="sample.Controller". However, I still get an error:
Caused by: javafx.fxml.LoadException:
/D:/JAVA/BMIC/out/production/BMIC/sample/sample.fxml:30

In your controller class you are importing awt classes for TextField and Label. Import the javafx classes.
Edit:
You have to remove the awt imports and insert the javafx imports:
package sample;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
public class Controller {
public TextField theight;
public TextField tweight;
public Label lbmi;
public Label lresult;
public void buttonclicked() {
double height;
double weight;
double bmi;
String result;
height = Double.parseDouble(theight.getText());
weight = Double.parseDouble(tweight.getText());
double square = height * height;
bmi = weight / square;
lbmi.setText("The BMI is " + bmi);
}
}

I'm developing a password manager program. When opening a new window in this program it throws an exception on the addEntry() mouse click event. I have a Main class that opens the main window (with sample.fxml) and a Controller class that manages to open the new window (with addNewEntryDialog.fxml). Here's my code:
Main.java
package sample;
import javafx.application.Application;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Modality;
import javafx.stage.Stage;
import java.io.IOException;
public class Main extends Application {
#Override
public void start(Stage primaryStage) throws Exception{
Parent root = FXMLLoader.load(getClass().getResource("/sample.fxml"));
primaryStage.setTitle("Password Manager");
primaryStage.setScene(new Scene(root, 800, 600));
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}
Controller.java
package sample;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.fxml.Initializable;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.stage.Stage;
import javafx.stage.StageStyle;
import java.io.IOException;
import java.net.URL;
import java.sql.*;
import java.util.ResourceBundle;
public class Controller implements Initializable {
public ObservableList<Data> data;
public TableView dbTable;
public TableColumn siteColumn, usernameColumn, passwordColumn;
public ToggleButton showPasswordToggle;
#Override
public void initialize(URL location, ResourceBundle resources) {
fillTable();
}
public void fillTable(){
data = FXCollections.observableArrayList();
String query = "SELECT * FROM accounts";
try {
Connection connection = connectToDatabase();
ResultSet resultSet = connection.createStatement().executeQuery(query);
while (resultSet.next()) {
data.add(new Data(resultSet.getString(1), resultSet.getString(2), resultSet.getString(3)));
}
siteColumn.setCellValueFactory(new PropertyValueFactory("site"));
usernameColumn.setCellValueFactory(new PropertyValueFactory("username"));
passwordColumn.setCellValueFactory(new PropertyValueFactory("password"));
dbTable.setItems(data);
} catch (SQLException e) {
e.printStackTrace();
}
}
#FXML
public void addEntry() throws IOException {
Stage stage = new Stage();
Parent root = FXMLLoader.load(getClass().getResource("/addEntryDialog.fxml"));
stage.setTitle("Add new entry");
stage.setScene(new Scene(root, 800, 600));
stage.show();
}
addEntryDialog.fxml
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<Pane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="200.0" prefWidth="400.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Controller">
<children>
<GridPane layoutX="28.0" layoutY="21.0" prefHeight="123.0" prefWidth="317.0">
<columnConstraints>
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" />
</columnConstraints>
<rowConstraints>
<RowConstraints minHeight="10.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" vgrow="SOMETIMES" />
</rowConstraints>
<children>
<Label layoutX="33.0" layoutY="26.0" text="Site:" />
<Label layoutX="28.0" layoutY="78.0" text="Username:" GridPane.rowIndex="1" />
<Label layoutX="44.0" layoutY="135.0" text="Password:" GridPane.rowIndex="2" />
<TextField fx:id="siteField" layoutX="150.0" layoutY="21.0" GridPane.columnIndex="1" />
<TextField fx:id="usernameField" layoutX="150.0" layoutY="73.0" GridPane.columnIndex="1" GridPane.rowIndex="1" />
<PasswordField fx:id="passwordField" layoutX="150.0" layoutY="123.0" GridPane.columnIndex="1" GridPane.rowIndex="2" />
</children>
</GridPane>
<Button layoutX="327.0" layoutY="163.0" mnemonicParsing="false" text="OK" />
<Button layoutX="246.0" layoutY="163.0" mnemonicParsing="false" text="Cancel" />
</children>
</Pane>
sample.fxml
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<?import javafx.geometry.Insets?>
<?import javafx.scene.layout.GridPane?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<Pane prefHeight="600.0" prefWidth="800.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Controller">
<children>
<TableView fx:id="dbTable" layoutX="4.0" layoutY="85.0" prefHeight="505.0" prefWidth="790.0">
<columns>
<TableColumn fx:id="siteColumn" prefWidth="263.0" text="Site" />
<TableColumn fx:id="usernameColumn" prefWidth="263.0" text="Username" />
<TableColumn fx:id="passwordColumn" prefWidth="263.0" text="Password" />
</columns>
</TableView>
<GridPane layoutX="14.0" layoutY="27.0" prefHeight="25.0" prefWidth="263.0">
<columnConstraints>
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" />
</columnConstraints>
<rowConstraints>
<RowConstraints minHeight="10.0" vgrow="SOMETIMES" />
</rowConstraints>
<children>
<Button fx:id="addNewEntry" layoutX="14.0" layoutY="14.0" mnemonicParsing="false" onMouseClicked="#addEntry" text="Add.." GridPane.columnIndex="0" />
<Button fx:id="removeEntry" layoutX="83.0" layoutY="14.0" mnemonicParsing="false" text="Remove.." GridPane.columnIndex="1" />
<Button fx:id="editEntry" layoutX="178.0" layoutY="14.0" mnemonicParsing="false" text="Edit.." GridPane.columnIndex="2" />
</children>
</GridPane>
<ToggleButton fx:id="showPasswordToggle" layoutX="671.0" layoutY="27.0" mnemonicParsing="false" text="Show Password" />
</children>
</Pane>
STACK TRACE
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:54)
at javafx.event.Event.fireEvent(Event.java:198)
at javafx.scene.Scene$ClickGenerator.postProcess(Scene.java:3470)
at javafx.scene.Scene$ClickGenerator.access$8100(Scene.java:3398)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3766)
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$354(GlassViewEventHandler.java:388)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:387)
at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
at com.sun.glass.ui.View.notifyMouse(View.java:937)
at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
at com.sun.glass.ui.gtk.GtkApplication.lambda$null$49(GtkApplication.java:139)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1771)
... 31 more
Caused by: javafx.fxml.LoadException:
/home/umberto/passwordManager/out/production/passwordManager/addEntryDialog.fxml
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.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 sample.Controller.addEntry(Controller.java:58)
... 41 more
Caused by: java.lang.NullPointerException
at sample.Controller.loadTableData(Controller.java:45)
at sample.Controller.initialize(Controller.java:30)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2548)
... 49 more

Look at your addEntryDialog.fxml file. There is definition of this view's controller:
<Pane ... fx:controller="sample.Controller>
JavaFX loads the view, looks for the controller and creates it. (At this moment another sample.Controller object is instantiated). After creating it sees that this controller implements Initializable interface, so it executes initialize method which in turn calls fillTable method and finally the statement siteColumn.setCellValueFactory(..) is reached. The problem is that there's no siteColumn for addEntryDialog.fxml view - it has not been binded since there's no element on view with that id.
Solution is to create proper controller for addEntryView.fxml and call it in xml fx:controller attribute.