JAVAFX BASICS - Introduction to Java Programming: Comprehensive Version - page 571

8
9 public class ShowPolygon extends Application {
10 @Override // Override the start method in the Application class
11 public void start(Stage primaryStage) {
12 // Create a pane, a polygon, and place polygon to pane
13 Pane pane = new Pane();
14 Polygon polygon = new Polygon();
15 pane.getChildren().add(polygon);
16 polygon.setFill(Color.WHITE);
17 polygon.setStroke(Color.BLACK);
18

create a pane
create a polygon
add polygon to pane

ObservableList<Double> list = polygon.getPoints(); get a list of points

19
20 final double WIDTH = 200 , HEIGHT = 200 ;

21 double centerX = WIDTH / 2 , centerY = HEIGHT / 2 ;

22 double radius = Math.min(WIDTH, HEIGHT) * 0.4 ;

23
24

// Add points to the polygon list

25 for ( int i = 0 ; i < 6 ; i++) {

26 list.add(centerX + radius * Math.cos( 2 * i * Math.PI / 6 )); add x- coordinate of a point

add y- coordinate of a point

27 list.add(centerY - radius * Math.sin( 2 * i * Math.PI / 6 ));

28 }
29
30 // Create a scene and place it in the stage
31 Scene scene = new Scene(pane, WIDTH, HEIGHT);
32 primaryStage.setTitle( " ShowPolygon " ); // Set the stage title
33 primaryStage.setScene(scene); // Place the scene in the stage
34 primaryStage.show(); // Display the stage
35 }
36 }

add pane to scene

The program creates a polygon (line 14) and adds it to a pane (line 15). The polygon
.getPoints() method returns an ObservableList<Double> (line 18), which contains
the add method for adding an element to the list (lines 26-27). Note that the value
passed to add(value) must be a double value. If an int value is passed, the int value
would be automatically boxed into an Integer . This would cause an error because the
ObservableList<Double> consists of Double elements.
The loop adds six points to the polygon (lines 25-28). Each point is represented by its
x - and y -coordinates. For each point, its x -coordinate is added to the polygon's list (line 26)
and then its y -coordinate is added to the list (line 27). The formula for computing the x - and
y -coordinates for a point in the hexagon is illustrated in Figure 14.40a.
If you replace Polygon by Polyline , the program displays a polyline as shown in
Figure 14.40b. The Polyline class is used in the same way as Polygon except that the start-
ing and ending point are not connected in Polyline .

14.27

✓ ✓

How do you display a text, line, rectangle, circle, ellipse, arc, polygon, and polyline?

Check

14.28

Write code fragments to display a string rotated 45 degrees in the center of the pane.

Point

14.29

Write code fragments to display a thick line of 10 pixels from ( 10 , 10 ) to ( 70 , 30 ).

14.30

Write code fragments to fill red color in a rectangle of width 100 and height 50 with
the upper-left corner at ( 10 , 10 ).

14.31

Write code fragments to display a round-cornered rectangle with width 100 , height
200 with the upper-left corner at ( 10 , 10 ), corner horizontal diameter 40 , and corner
vertical diameter 20 .

14.32

Write code fragments to display an ellipse with horizontal radius 50 and vertical
radius 100 .

14.33

Write code fragments to display the outline of the upper half of a circle with radius 50 .