JavaFX ChoiceBox handle selection event

import javafx.application.Application;
import javafx.beans.value.ChangeListener;
import javafx.collections.FXCollections;
import javafx.scene.Scene;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.control.Button;
import javafx.scene.control.ChoiceBox;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.StackPane;
import javafx.scene.paint.Color;
import javafx.stage.Stage;

public class Main extends Application {
   public static void main(String[] args) {
      Application.launch(Main.class, args);
   }/*  www.  j a  v a  2  s.  c  o m*/

   @Override
   public void start(Stage primaryStage) {
      StackPane root = new StackPane();
      Canvas canvas = new Canvas(300, 300);
      final GraphicsContext graphicsContext = canvas.getGraphicsContext2D();

      final Button resetButton = new Button("Reset");
      resetButton.setOnAction(actionEvent -> {
         graphicsContext.clearRect(1, 1, graphicsContext.getCanvas().getWidth() - 2,
               graphicsContext.getCanvas().getHeight() - 2);
      });
      resetButton.setTranslateX(10);

      // Set up the pen color chooser
      ChoiceBox<String> colorChooser = new ChoiceBox<>(
            FXCollections.observableArrayList("Black", "Blue", "Red", "Green", "Brown", "Orange"));
      // Select the first option by default
      colorChooser.getSelectionModel().selectFirst();

      colorChooser.getSelectionModel().selectedIndexProperty().addListener((ChangeListener) (ov, old, newval) -> {
         Number idx = (Number) newval;
         Color newColor;
         switch (idx.intValue()) {
         case 0:
            newColor = Color.BLACK;
            break;
         case 1:
            newColor = Color.BLUE;
            break;
         case 2:
            newColor = Color.RED;
            break;
         case 3:
            newColor = Color.GREEN;
            break;
         case 4:
            newColor = Color.BROWN;
            break;
         case 5:
            newColor = Color.ORANGE;
            break;
         default:
            newColor = Color.BLACK;
            break;
         }
         graphicsContext.setStroke(newColor);

      });
      colorChooser.setTranslateX(5);

      ChoiceBox<String> sizeChooser = new ChoiceBox<>(FXCollections.observableArrayList("1", "2", "3", "4", "5"));
      // Select the first option by default
      sizeChooser.getSelectionModel().selectFirst();

      sizeChooser.getSelectionModel().selectedIndexProperty().addListener((ChangeListener) (ov, old, newval) -> {
         Number idx = (Number) newval;

         switch (idx.intValue()) {
         case 0:
            graphicsContext.setLineWidth(1);
            break;
         case 1:
            graphicsContext.setLineWidth(2);
            break;
         case 2:
            graphicsContext.setLineWidth(3);
            break;
         case 3:
            graphicsContext.setLineWidth(4);
            break;
         case 4:
            graphicsContext.setLineWidth(5);
            break;
         default:
            graphicsContext.setLineWidth(1);
            break;
         }
      });
      sizeChooser.setTranslateX(5);

      canvas.addEventHandler(MouseEvent.MOUSE_PRESSED, (MouseEvent event) -> {
         graphicsContext.beginPath();
         graphicsContext.moveTo(event.getX(), event.getY());
         graphicsContext.stroke();
      });

      canvas.addEventHandler(MouseEvent.MOUSE_DRAGGED, (MouseEvent event) -> {
         graphicsContext.lineTo(event.getX(), event.getY());
         graphicsContext.stroke();
      });

      canvas.addEventHandler(MouseEvent.MOUSE_RELEASED, (MouseEvent event) -> {
      });

      HBox buttonBox = new HBox();
      buttonBox.getChildren().addAll(colorChooser, sizeChooser, resetButton);

      initDraw(graphicsContext, canvas.getLayoutX(), canvas.getLayoutY());

      BorderPane container = new BorderPane();
      container.setTop(buttonBox);

      container.setCenter(canvas);

      root.getChildren().add(container);

      Scene scene = new Scene(root, 400, 400);
      primaryStage.setTitle("java2s.com");
      primaryStage.setScene(scene);
      primaryStage.show();
   }

   private void initDraw(GraphicsContext gc, double x, double y) {
      double canvasWidth = gc.getCanvas().getWidth();
      double canvasHeight = gc.getCanvas().getHeight();

      gc.fill();
      gc.strokeRect(x, // x of the upper left corner
            y, // y of the upper left corner
            canvasWidth, // width of the rectangle
            canvasHeight); // height of the rectangle

   }
}