Main:

package be.vincent_nagy.oxo;

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(getClass().getResource("oxo.fxml"));

        Parent root = loader.load();
        Scene mainScene = new Scene(root,600,600);

        primaryStage.setTitle("OXO Spel");
        primaryStage.setScene(mainScene);

        primaryStage.show();

        //Hier geef ik de controller toegang tot de main app.
        OxoController controller = loader.getController();
        controller.setMain(this);

    }


    public static void main(String[] args) {
        launch(args);
    }
}







Controller:
package be.vincent_nagy.oxo;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.Button;
import javafx.scene.layout.GridPane;

public class OxoController {

    @FXML
    private GridPane mainGrid;

    @FXML
    private Button button5;

    @FXML
    private Button button3;

    @FXML
    private Button button2;

    @FXML
    private Button button4;

    @FXML
    private Button button6;

    @FXML
    private Button button7;

    @FXML
    private Button button8;

    @FXML
    private Button button9;

    @FXML
    private Button button1;

    //Referentie naar de main applicatie
    private Main main;

    //Constructor wordt opgeroepen voor de initialize() methode
    public OxoController(){

    }

    //Deze methode wordt automatisch opgeroepen NADAT de FXML file geladen is. Vanaf hier heb ik dus toegang
    // tot de @FXML properties van deze controller
    @FXML
    private void initialize(){

    }

    //Referentie naar de main applicatie. Aanroeping vanuit main
    public void setMain(Main main){
        this.main = main;
    }


    @FXML
    void handleButtonAction(ActionEvent event) {
        if(event.getSource() instanceof Button){
            Button src = (Button) event.getSource();

            //send the src up to main or handle the game code here?
        }
    }


}






FXML:
<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.Button?>
<?import javafx.scene.layout.ColumnConstraints?>
<?import javafx.scene.layout.GridPane?>
<?import javafx.scene.layout.RowConstraints?>

<GridPane fx:id="mainGrid" alignment="center" gridLinesVisible="true" minHeight="600.0" minWidth="600.0" xmlns="http://javafx.com/javafx/8.0.111" xmlns:fx="http://javafx.com/fxml/1" fx:controller="be.vincent_nagy.oxo.OxoController">
   <rowConstraints>
      <RowConstraints maxHeight="200.0" minHeight="200.0" prefHeight="200.0" />
      <RowConstraints maxHeight="200.0" minHeight="200.0" prefHeight="200.0" />
      <RowConstraints maxHeight="200.0" minHeight="200.0" prefHeight="200.0" />
   </rowConstraints>
   <columnConstraints>
      <ColumnConstraints maxWidth="200.0" minWidth="200.0" prefWidth="200.0" />
      <ColumnConstraints maxWidth="200.0" minWidth="200.0" prefWidth="200.0" />
      <ColumnConstraints maxWidth="200.0" minWidth="200.0" prefWidth="200.0" />
   </columnConstraints>
   <children>
      <Button fx:id="button5" mnemonicParsing="false" onAction="#handleButtonAction" prefHeight="200.0" prefWidth="200.0" GridPane.columnIndex="1" GridPane.rowIndex="1" />
      <Button fx:id="button3" mnemonicParsing="false" onAction="#handleButtonAction" prefHeight="200.0" prefWidth="200.0" GridPane.columnIndex="2" />
      <Button fx:id="button2" mnemonicParsing="false" onAction="#handleButtonAction" prefHeight="200.0" prefWidth="200.0" GridPane.columnIndex="1" />
      <Button fx:id="button4" mnemonicParsing="false" onAction="#handleButtonAction" prefHeight="200.0" prefWidth="200.0" GridPane.rowIndex="1" />
      <Button fx:id="button6" mnemonicParsing="false" onAction="#handleButtonAction" prefHeight="200.0" prefWidth="200.0" GridPane.columnIndex="2" GridPane.rowIndex="1" />
      <Button fx:id="button7" mnemonicParsing="false" onAction="#handleButtonAction" prefHeight="200.0" prefWidth="200.0" GridPane.rowIndex="2" />
      <Button fx:id="button8" mnemonicParsing="false" onAction="#handleButtonAction" prefHeight="200.0" prefWidth="200.0" GridPane.columnIndex="1" GridPane.rowIndex="2" />
      <Button fx:id="button9" mnemonicParsing="false" onAction="#handleButtonAction" prefHeight="200.0" prefWidth="200.0" GridPane.columnIndex="2" GridPane.rowIndex="2" />
      <Button fx:id="button1" mnemonicParsing="false" onAction="#handleButtonAction" prefHeight="200.0" prefWidth="200.0" />
   </children>
</GridPane>