Java FX GUI can´t load unknown source - javafx-8

Question

I hope someone can help me with my problem.
The problem is that when I start the program I always get an exception saying that the source file can´t be found. I already used the internet for resolving the problem by using the exception message as search argument for google. But I didn´t find a solution.
Exception Message:
java.lang.NullPointerException: Location is required.
at javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
at javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
at javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
at javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
at javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
at javafx.fxml.FXMLLoader.load(Unknown Source)
at com.kw.overtaker_monitoring.Main.start(Main.java:18)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$153(Unknown Source)
at com.sun.javafx.application.LauncherImpl$$Lambda$51/924394080.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$166(Unknown Source)
at com.sun.javafx.application.PlatformImpl$$Lambda$45/1051754451.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$null$164(Unknown Source)
at com.sun.javafx.application.PlatformImpl$$Lambda$47/389777815.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$165(Unknown Source)
at com.sun.javafx.application.PlatformImpl$$Lambda$46/1775282465.run(Unknown Source)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(Unknown Source)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$141(Unknown Source)
at com.sun.glass.ui.win.WinApplication$$Lambda$37/1109371569.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Error Message in SceneBuilder:
No injectable field found in FXML Controller class for the id 'btnSelectDatabaseFile'
For further information, I´ll give you the code of my classes below
Main.java (Main class):
package com.kw.overtaker_monitoring;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.stage.Stage;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.layout.BorderPane;
public class Main extends Application
{
#Override
public void start(Stage primaryStage)
{
try
{
Parent root = FXMLLoader.load(getClass().getResource("MainWindow.fxml"));
Scene scene = new Scene(root);
primaryStage.setScene(scene);
primaryStage.show();
}
catch(Exception e)
{
e.printStackTrace();
}
}
public static void main(String[] args)
{
launch(args);
}
}
MainWindow.fxml (GUI File):
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.shape.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.layout.AnchorPane?>
<AnchorPane prefHeight="561.0" prefWidth="830.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="kw.IO.Controller">
<children>
<Accordion layoutX="22.0" layoutY="68.0" prefHeight="18.0" prefWidth="7.0" />
<Accordion layoutX="14.0" layoutY="14.0" prefHeight="639.0" prefWidth="889.0" AnchorPane.bottomAnchor="16.0" AnchorPane.leftAnchor="14.0" AnchorPane.rightAnchor="14.0" AnchorPane.topAnchor="14.0">
<panes>
<TitledPane animated="false" text="First">
<content>
<AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="187.0" prefWidth="234.0">
<children>
<Button id="btnAddSizeToFolderName" fx:id="btnAddSizeToFolderName" layoutX="142.0" layoutY="84.0" mnemonicParsing="false" onAction="#RunFolderRenaming" text="Add size to foldername" />
<TextField id="txtSrcPath" fx:id="txtSrcPath" layoutX="112.0" layoutY="14.0" prefHeight="25.0" prefWidth="671.0" />
<Label layoutX="22.0" layoutY="18.0" text="sourcepath" />
<Label layoutX="22.0" layoutY="48.0" text="destinationpath" />
<TextField id="txtDestPath" fx:id="txtDestPath" layoutX="112.0" layoutY="44.0" prefHeight="25.0" prefWidth="672.0" />
<CheckBox fx:id="chkIncludeSubDirs" layoutX="22.0" layoutY="88.0" mnemonicParsing="false" text="Only subdirs" />
<Separator layoutX="-5.0" layoutY="75.0" prefHeight="3.0" prefWidth="808.0" />
<Separator layoutX="-4.0" layoutY="116.0" prefHeight="3.0" prefWidth="808.0" />
<TextField id="txtSrcPath" fx:id="txtOldFileName" layoutX="14.0" layoutY="126.0" prefHeight="25.0" prefWidth="176.0" />
<TextField id="txtSrcPath" fx:id="txtReplaceWith" layoutX="282.0" layoutY="126.0" prefHeight="25.0" prefWidth="176.0" />
<Label layoutX="212.0" layoutY="130.0" text="replace with" />
<Button id="btnAddSizeToFolderName" fx:id="btnReplace" layoutX="469.0" layoutY="126.0" mnemonicParsing="false" onAction="#RunFileRenaming" text="replace from all files in folder" />
</children>
</AnchorPane>
</content>
</TitledPane>
<TitledPane animated="false" text="Movie Database Tools">
<content>
<AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0">
<children>
<TextField editable="false" layoutX="141.0" layoutY="10.0" prefHeight="25.0" prefWidth="651.0" />
<Button layoutX="14.0" layoutY="10.0" mnemonicParsing="false" onMouseClicked="#btnSelectDatabaseFile_Clicked" text="Select Database File" />
</children></AnchorPane>
</content>
</TitledPane>
<TitledPane animated="false" text="untitled 3">
<content>
<AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="434.0" prefWidth="731.0" />
</content>
</TitledPane>
</panes>
</Accordion>
</children>
</AnchorPane>
Controller.java (Controller class):
package kw.IO;
import java.net.URL;
import java.util.ResourceBundle;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Button;
import javafx.scene.control.CheckBox;
import javafx.scene.control.TextField;
public class Controller implements Initializable
{
#FXML
private Button btnAddSizeToFolderName;
#FXML
private Button btnReplace;
#FXML
private Button btnSelectDatabaseFile;
#FXML
private TextField txtSrcPath;
#FXML
private TextField txtOldFileName;//TODO: übergeben
#FXML
private TextField txtReplaceWith;//TODO: übergeben
#FXML
private CheckBox chkIncludeSubDirs;
private Operator operator = new Operator();
#Override
public void initialize(URL location, ResourceBundle resources)
{
// TODO Auto-generated method stub
}
// this starts the a thread with the function of renaming folders by adding their size to them
public void RunFolderRenaming(ActionEvent event)
{
System.out.println("Button wurde geklickt!");
System.out.println(txtSrcPath.getText());
operator.StartFolderRenaming(txtSrcPath.getText().toString(), chkIncludeSubDirs.isSelected());
}
public void RunFileRenaming(ActionEvent event)
{
System.out.println("File renaming button clicked!");
operator.ReplaceFromFiles(txtSrcPath.getText(), txtOldFileName.getText(), txtReplaceWith.getText());
}
public void btnSelectDatabaseFile(ActionEvent btnSelectDatabaseFile_Clicked)
{
System.out.println("Button Select Database File was clicked!");
}
}
Please help me with my problem?
Kind regards
Prouder