(Sierpinski triangle) Revise Listing 1 to develop a program that lets the user use the + a...

(Sierpinski triangle) Revise Listing 1 to develop a program that lets the user use the + and – buttons to increase or decrease the current order by 1, as shown in Figure 1a. The initial order is 0. If the current order is 0, the Decrease button is ignored.

FIGURE 1 (a) Programming Exercise uses the + and – buttons to increase or decrease the current order by 1.

LISTING 1 SierpinskiTriangle.java

1 import javafx.application.Application;
2 import javafx.geometry.Point2D;
3 import javafx.geometry.Pos;
4 import javafx.scene.Scene;
5 import javafx.scene.control.Label;
6 import javafx.scene.control.TextField;
7 import javafx.scene.layout.BorderPane;
8 import javafx.scene.layout.HBox;
9 import javafx.scene.layout.Pane;
10 import javafx.scene.paint.Color;
11 import javafx.scene.shape.Polygon;
12 import javafx.stage.Stage;
13
14 public class SierpinskiTriangle extends Application {
15 @Override // Override the start method in the Application class
16 public void start(Stage primaryStage) {
17 SierpinskiTrianglePane trianglePane = new SierpinskiTrianglePane();
18 TextField tfOrder = new TextField();
19 tfOrder.setOnAction(
29 BorderPane borderPane = new BorderPane();
30 borderPane.setCenter(trianglePane);
31 borderPane.setBottom(hBox);
32
33 // Create a scene and place it in the stage
34 Scene scene = new Scene(borderPane, 200, 210);
35 primaryStage.setTitle("SierpinskiTriangle"); // Set the stage title
36 primaryStage.setScene(scene); // Place the scene in the stage
37 primaryStage.show(); // Display the stage
38
39 scene.widthProperty().addListener(ov -> trianglePane.paint());
40 scene.heightProperty().addListener(ov -> trianglePane.paint());
41 }
42
43 /** Pane for displaying triangles */
44 static class SierpinskiTrianglePane extends Pane {
45 private int order = 0;
46
47 /** Set a new order */
48 public void setOrder(int order) {
49 this.order = order;
50 paint();
51 }
52
53 SierpinskiTrianglePane() {
54 }
55
56 protected void paint() {
57 // Select three points in proportion to the pane size
58 Point2D p1 = new Point2D(getWidth() / 2, 10);
59 Point2D p2 = new Point2D(10, getHeight() - 10);
60 Point2D p3 = new Point2D(getWidth() - 10, getHeight() - 10);
61
62 this.getChildren().clear(); // Clear the pane before redisplay
63
64 displayTriangles(order, p1, p2, p3);
65 }
66
67 private void displayTriangles(int order, Point2D p1,
68 Point2D p2, Point2D p3) {
69 if (order == 0) {
70 // Draw a triangle to connect three points
71 Polygon triangle = new Polygon();
72 triangle.getPoints().addAll(p1.getX(), p1.getY(), p2.getX(),
73 p2.getY(), p3.getX(), p3.getY());
74 triangle.setStroke(Color.BLACK);
75 triangle.setFill(Color.WHITE);
76
77 this.getChildren().add(triangle);
78 }
79 else {
80 // Get the midpoint on each edge in the triangle
81 Point2D p12 = p1.midpoint(p2);
82 Point2D p23 = p2.midpoint(p3);
83 Point2D p31 = p3.midpoint(p1);
84
85 // Recursively display three triangles
86 displayTriangles(order - 1, p1, p12, p31);
87 displayTriangles(order - 1, p12, p2, p23);
88 displayTriangles(order - 1, p31, p23, p3);
89 }
90 }
91 }
92 }