How to count from TextField in javaFx?

Question

Java

Hello, I started to understand javafx, there was a problem with reading information from a textfield and outputting it to a label, I implemented it myself without controller.java and fxml, but I would like to use them, I want to understand how the controller works, etc., so as not to write everything in main'e. Thanks in advance
1) this is how it works, without a controller and fxml, everything is done manually

@Override
    public void start(Stage stage) {
        Group root = new Group();
        Scene scene = new Scene(root, 300, 150);
        stage.setScene(scene);
        stage.setTitle("Text Field Sample");

        GridPane grid = new GridPane();
        grid.setPadding(new Insets(10, 10, 10, 10));
        grid.setVgap(5);
        grid.setHgap(5);

        scene.setRoot(grid);

        final TextField name = new TextField();
        name.setPromptText("Enter your first name.");
        name.setPrefColumnCount(10);
        name.getText();
        GridPane.setConstraints(name, 0, 0);
        grid.getChildren().add(name);

        final TextField lastName = new TextField();
        lastName.setPromptText("Enter your last name.");
        GridPane.setConstraints(lastName, 0, 1);
        grid.getChildren().add(lastName);

        final TextField comment = new TextField();
        comment.setPrefColumnCount(15);
        comment.setPromptText("Enter your comment.");
        GridPane.setConstraints(comment, 0, 2);
        grid.getChildren().add(comment);

        Button submit = new Button("Submit");
        GridPane.setConstraints(submit, 1, 0);
        grid.getChildren().add(submit);

        Button clear = new Button("Clear");
        GridPane.setConstraints(clear, 1, 1);
        grid.getChildren().add(clear);

        final Label label = new Label();
        GridPane.setConstraints(label, 0, 3);
        GridPane.setColumnSpan(label, 2);
        grid.getChildren().add(label);

        submit.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent e) {
                if (
                    (comment.getText() != null && !comment.getText().isEmpty())
                ) {
                    label.setText(name.getText() + " " +
                        lastName.getText() + ", "
                        + "thank you for your comment!");
                } else {
                    label.setText("You have not left a comment.");
                }
            }
        });

        clear.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent e) {
                name.clear();
                lastName.clear();
                comment.clear();
                label.setText(null);
            }
        });

        stage.show();
    }

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

2) and when I do this, it does not work

<GridPane alignment="center" hgap="10" prefHeight="150.0" prefWidth="303.0" vgap="10" xmlns="http://javafx.com/javafx/8.0.112" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Controller">
   <columnConstraints>
      <ColumnConstraints />
   </columnConstraints>
   <rowConstraints>
      <RowConstraints />
      <RowConstraints />
      <RowConstraints />
      <RowConstraints />
   </rowConstraints>
   <TextField id="tittel" fx:id="tittel" layoutX="120.0" layoutY="64.0" onAction="#handleButton1Action" promptText="Tittel" GridPane.rowIndex="1" />
   <Button id="button" fx:id="button1" layoutX="100.0" layoutY="50.0" onAction="#handleButton1Action" prefHeight="25.0" prefWidth="70.0" text="Click me" GridPane.rowIndex="3" />
</GridPane>

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");
        Scene scene = new Scene(root, 300, 275, Color.RED);
        primaryStage.setScene(scene);
        primaryStage.show();
    }


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

Answer 1

Because you have a newly created JTextField, instead of "caught" from FXML:
Remove this.
In addition, in FXML you have id=tittel, which means that the field name must be tittel, not textField, otherwise it will not be picked up.
Are you going to write JavaFX for Android? Seriously?