LISTS, STACKS, QUEUES, AND PRIORITY QUEUES - Introduction to Java Programming: Comprehensive Version - page 779

25 Button btSubtract = new Button( "-" );
26 HBox hBox = new HBox( 10 );
27 hBox.getChildren().addAll(btAdd, btSubtract);
28 hBox.setAlignment(Pos.CENTER);
29
30

add buttons to HBox

// Add or remove a ball

31 btAdd.setOnAction(e -> ballPane.add());

add a ball
remove a ball 32 btSubtract.setOnAction(e -> ballPane.subtract());

33
34

// Pause and resume animation

35 ballPane.setOnMousePressed(e -> ballPane.pause()); pause animation

resume animation

36 ballPane.setOnMouseReleased(e -> ballPane.play());

37
38 // Use a scroll bar to control animation speed
39 ScrollBar sbSpeed = new ScrollBar();
40 sbSpeed.setMax( 20 );
41 sbSpeed.setValue( 10 );
42

create a scroll bar

ballPane.rateProperty().bind(sbSpeed.valueProperty());

bind animation rate

43
44 BorderPane pane = new BorderPane();
45 pane.setCenter(ballPane);
46 pane.setTop(sbSpeed);
47 pane.setBottom(hBox);
48
49 // Create a scene and place the pane in the stage
50 Scene scene = new Scene(pane, 250 , 150 );
51 primaryStage.setTitle( "MultipleBounceBall" ); // Set the stage title
52 primaryStage.setScene(scene); // Place the scene in the stage
53 primaryStage.show(); // Display the stage
54 }
55
56

private class MultipleBallPane extends Pane {

57 private Timeline animation;

58
59 public MultipleBallPane() {
60 // Create an animation for moving the ball
61 animation = new Timeline(
62 new KeyFrame(Duration.millis( 50 ), e -> moveBall()));
63 animation.setCycleCount(Timeline.INDEFINITE);
64 animation.play(); // Start animation

65 }
66
67 public void add() {
68 Color color = new Color(Math.random(),
69 Math.random(), Math.random(), 0.5 );
70

getChildren().add( new Ball( 30 , 30 , 20 , color)); add a ball to pane

71 }
72
73 public void subtract() {
74 if (getChildren().size() > 0 ) {
75 getChildren().remove(getChildren().size() - 1 );
76 }
77 }
78
79 public void play() {
80 animation.play();
81 }
82
83

remove a ball

public void pause() {