Show Polygon

// Ricardo Santiago
// 4/6/16
// CSCI-112
// Homework13
// display polygon with buttons to add or subtract sides

import javafx.application.Application;
import javafx.collections.ObservableList;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextArea;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.scene.paint.Color;
import javafx.scene.shape.Polygon;
import javafx.stage.Stage;

public class ShowPolygon extends Application {

    static int numOfSides = 6;
    final double WIDTH = 200;
    final double HEIGHT = 200;
    double radius = Math.min(WIDTH, HEIGHT) * 0.4;
    double centerX = WIDTH / 2;
    double centerY = HEIGHT / 2;
    Button btnAdd, btnSub;
    ObservableList<Double> list;
    BorderPane root = new BorderPane();
    Polygon polygon = new Polygon();
    TextArea showNumOfSides = new TextArea("" + numOfSides);

    @Override
    public void start(Stage primaryStage) throws Exception {

        root.setBottom(getBottomHBox());

        list = polygon.getPoints();
        polygon.setFill(Color.WHITE);
        polygon.setStroke(Color.BLACK);
        root.setCenter(polygon);

        generatePolygon(numOfSides);

        Scene scene = new Scene(root, 200, 200);
        primaryStage.setTitle("Show Polygon");
        primaryStage.setScene(scene);
        primaryStage.show();

        btnAdd.setOnMouseClicked(e -> {
            generatePolygon(numOfSides++);
        });

        btnSub.setOnMouseClicked(e -> {
            generatePolygon(numOfSides--);
        });
    }

    public void generatePolygon(int sides) {
        list.clear();
        root.setCenter(polygon);

        for (int i = 0; i < numOfSides; i++) {
            list.add(centerX + radius * Math.cos(2 * i * Math.PI / numOfSides));
            list.add(centerY + radius * Math.sin(2 * i * Math.PI / numOfSides));
        }

    }

    public int getNumOfSides() {
        return numOfSides;
    }

    private HBox getBottomHBox() {
        HBox bottomHBox = new HBox();
        bottomHBox.setAlignment(Pos.CENTER);
        bottomHBox.setSpacing(10.0);
        root.setPadding(new Insets(10));
        btnAdd = new Button("+");
        btnSub = new Button("-");
        bottomHBox.getChildren().addAll(btnAdd, btnSub);

        return bottomHBox;

    }

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

}