JavaFX - refreshing a chart

Question

I have two classes ViewTaskTest and ControllerTaskTest. The view has two buttons, one to create a random point and the other to start the controller. After the start, the controller will place 10 random points to the chart inside the view. But the points are visible only at the end. I want to see the points being placed one by one. I know, that I have to use somehow the Task-functions and I am struggling to understand this concept.

This is the ViewTaskTest-class:

package View;

import Controller.ControllerTaskTest;
import javafx.concurrent.Task;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.chart.Axis;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.ScatterChart;
import javafx.scene.chart.XYChart;
import javafx.scene.control.Button;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class ViewTaskTest{

    ScatterChart<Number, Number> scatterChart;
    XYChart.Series<Number, Number> series = new XYChart.Series<Number, Number>();  
    Axis<Number> xAxis = new NumberAxis(0, 10, 2); ;
    Axis<Number> yAxis = new NumberAxis(0, 10, 2); ; 
    Button buttonAddRandomPoint = new Button("Add random point");
    Button buttonStartControllerTest = new Button("Start controller");
    private final int MAIN_WINDOW_HEIGHT = 800;
    private final int MAIN_WINDOW_WIDTH = 800;
    ControllerTaskTest controller;

    public ViewTaskTest() {

    }

    public void setController(ControllerTaskTest controller) {
        this.controller = controller;
    }

    public void fillStage(Stage stage)  {

        stage.setTitle("QuickPID");
        stage.setMinHeight(MAIN_WINDOW_HEIGHT);
        stage.setMinWidth(MAIN_WINDOW_WIDTH);
        stage.setMaxHeight(MAIN_WINDOW_HEIGHT);
        stage.setMaxWidth(MAIN_WINDOW_WIDTH);
        Scene sceneOne = new Scene(new Group());
        scatterChart = new ScatterChart<Number, Number>(xAxis, yAxis);
        scatterChart.getData().add(series);

        // add a random point 
        buttonAddRandomPoint.setOnAction(e -> {
            Double x = new Double(0.0);
            Double y = new Double(0.0);
            try{
                x = Math.random() * 10;
                y = Math.random() * 10;
                series.getData().add(new XYChart.Data<Number, Number>(x, y)); 
            } catch (Exception ex) {
                System.out.println("Error");
            }

        });

        buttonStartControllerTest.setOnAction(e -> {
            controller.startAddingPoints();
        });

        VBox vboxButtons = new VBox(5);
        HBox hboxMain = new HBox(5);
        vboxButtons.getChildren().addAll(buttonAddRandomPoint, buttonStartControllerTest);
        vboxButtons.setAlignment(Pos.BOTTOM_LEFT);
        vboxButtons.setPadding(new Insets(10));
        hboxMain.getChildren().addAll(scatterChart, vboxButtons);
        sceneOne.setRoot(hboxMain);
        stage.setScene(sceneOne);
    }

    public void addRandomPointFromController(Double x, Double y) {
        System.out.println("starting view task");
        Task<Integer> task = new Task<Integer>() {
            @Override protected Integer call() throws Exception {
                series.getData().add(new XYChart.Data<Number, Number>(x, y));
                return 0;
            }
        };  

        task.run();
    }
}

Here is the ControllerTestTask-Class:

package Controller;

import View.ViewTaskTest;
import javafx.concurrent.Task;

public class ControllerTaskTest {

    ViewTaskTest view;

    public ControllerTaskTest() {
    }

    public void setView(ViewTaskTest view) {
        this.view = view;
    }

    public void startAddingPoints() {
        System.out.println("starting controller task");
        Task<Integer> task = new Task<Integer>() {
            @Override protected Integer call() throws Exception {
                for(int i = 0; i < 10; i++) {
                    Double x = Math.random() * 10;
                    Double y = Math.random() * 10;
                    view.addRandomPointFromController(x, y);
                    System.out.println("Adding point x = " + x + " and y = " + y);
                    Thread.sleep(100);
                }
                return 0;
            }
        };  
        task.run();
    }
}

Here is the main-class:

package Test;

import Controller.ControllerTaskTest;
import View.ViewTaskTest;
import javafx.application.Application;
import javafx.stage.Stage;

public class Test extends Application{

    private ViewTaskTest view= new ViewTaskTest();
    private ControllerTaskTest controller = new ControllerTaskTest();

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

    @Override
    public void start(Stage stage) throws Exception {
        view.setController(controller);
        controller.setView(view);
        stage.show();
        view.fillStage(stage);
    }
}

Some please explain me what I am doing wrong. I am experimenting with the Thread-funcitons but I cant solve my problem.