How to use Javafx and scenebuilder to draw on canvas (Group element) - javafx

Question

i am new to scenebuilder and fx and need some help.
I have the class Puffer , TestMain and MainViewController.
I tried to paint on the canvas and it worked.I tried Puffer and it worked too.
Now I wanted to use scenebuilder and have my problems.I would like to draw the Group from Puffer on the canvas with a button and don't know what's the best solution.I already tried to modify Puffer without any result.
public class Puffer {
Group root = new Group();
public void draw() {
for (int x = 0; x < 800; x++) {
for (int y = 0; y < 600; y++) {
Complex z0 = new Complex(0.11, 0.123); //!!!!!!!!!!!!! under 1
Complex c = new Complex(x / 400.0 - 2, 1 - y / 400.0);
if (isBounded(iterate(z0, c))) {
drawPoint(x, y, root);
}
}
}
// primaryStage.setScene(new Scene(root, 800, 600));
// primaryStage.show();
}
public void drawPoint(int x, int y, Group root) {
int max = 255;
int min = 0;
int range = max - min + 1;
Line line = new Line(x, y, x, y);
// line.setStroke(Color.rgb((int)(Math.random() * range) + min,(int)(Math.random() * range) + min,(int)(Math.random() * range) + min));
root.getChildren().add(line);
}
public Complex iterate(Complex z0, Complex c) {
Complex zn = z0;
for (int i = 0; i < 20; i++) {
zn.square().add(c);
}
return zn;
}
public boolean isBounded(Complex zn) {
return zn.module() < 2;
}
public class MainViewController {
#FXML
Canvas canvas;
// Event Listener on Button.onAction
#FXML
public void btnOkClicked(ActionEvent event) {
System.out.println("Test");
}
#FXML
public void drawCanvas(){
// GraphicsContext gc = canvas.getGraphicsContext2D();
// gc.setLineWidth(3);
// gc.setStroke(Color.BLACK);
// System.out.println("drawCanvas");
//
// try {
// canvas.setOnMousePressed(event -> {
// System.out.println("Mouse click");
// gc.beginPath();
// gc.lineTo(event.getSceneX(), event.getSceneY());
// gc.stroke();
// });
//
// canvas.setOnMouseDragged(event -> {
// System.out.println("Mouse dragged");
// gc.lineTo(event.getSceneX(), event.getSceneY());
// gc.stroke();
// });
// }catch (Exception e){
// System.out.println(e);
// System.exit(0);
// }
}
public class TestMain extends Application {
#Override
public void start(Stage s1) throws Exception {
try {
Parent root = FXMLLoader.load(getClass().getResource("MainView.fxml"));
Scene scene = new Scene(root);
s1.setTitle("Test");
s1.setScene(scene);
s1.show();
}catch(Exception ex) {
ex.printStackTrace();
}
}
public static void main(String[] args) {
launch(args);
}