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HarryDulaneyHarryDulaney
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new chapters and exercise solutions
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‎ch_15/Exercise15_21.java

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package ch_15;
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import javafx.application.Application;
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import javafx.geometry.Point2D;
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import javafx.scene.Scene;
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import javafx.scene.layout.Pane;
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import javafx.scene.shape.Circle;
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import javafx.scene.shape.Line;
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import javafx.scene.text.Text;
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import javafx.stage.Stage;
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/**
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* 15.21 (Drag points) Draw a circle with three random points on the circle. Connect
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* the points to form a triangle. Display the angles in the triangle. Use the mouse
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* to drag a point along the perimeter of the circle. As you drag it, the triangle and
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* angles are redisplayed dynamically, as shown in Figure 15.30b. For computing
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* angles in a triangle, see Listing 4.1.
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* <p>
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* The parametric equation for a circle is
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* x = cx + r * cos(a)
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* y = cy + r * sin(a)
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* where r is the radius, (cx, cy) the center of the circle, and a, an angle in radians.
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*/
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public class Exercise15_21 extends Application {
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private double radius = 10;
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private int centerX = 200;
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private int centerY = 125;
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private int radiusMainCircle = 100;
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private Pane pane = new Pane();
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private Circle outlineCircle = new Circle(centerX, centerY, radiusMainCircle);
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private Circle[] points = new Circle[3];
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private Line line1 = new Line();
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private Line line2 = new Line();
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private Line line3 = new Line();
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private Text[] text = {new Text(), new Text(), new Text()};
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@Override
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public void start(Stage primaryStage) {
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draw();
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pane.getChildren().addAll(points[0], points[1], points[2],
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line1, line2, line3, text[0], text[1], text[2]);
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Scene scene = new Scene(pane, 400, 250);
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primaryStage.setTitle(getClass().getName());
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primaryStage.setScene(scene);
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primaryStage.show();
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points[0].setOnMouseDragged(e -> {
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if (points[0].contains(e.getX(), e.getY())) {
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// Recompute and display angles
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points[0].setCenterX(e.getX());
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points[0].setCenterY(e.getY());
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setLines();
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}
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});
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points[1].setOnMouseDragged(e -> {
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if (points[1].contains(e.getX(), e.getY())) {
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// Recompute and display angles
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points[1].setCenterX(e.getX());
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points[1].setCenterY(e.getY());
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setLines();
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}
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});
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points[2].setOnMouseDragged(e -> {
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if (points[2].contains(e.getX(), e.getY())) {
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// Recompute and display angles
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points[2].setCenterX(e.getX());
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points[2].setCenterY(e.getY());
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setLines();
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}
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});
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}
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void draw() {
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points[0] = new Circle(40, 40, 10);
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points[1] = new Circle(140, 40, 10);
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points[2] = new Circle(60, 140, 10);
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setLines();
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}
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private void setLines() {
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line1.setStartX(points[0].getCenterX());
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line1.setStartY(points[0].getCenterY());
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line1.setEndX(points[1].getCenterX());
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line1.setEndY(points[1].getCenterY());
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line2.setStartX(points[0].getCenterX());
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line2.setStartY(points[0].getCenterY());
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line2.setEndX(points[2].getCenterX());
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line2.setEndY(points[2].getCenterY());
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line3.setStartX(points[1].getCenterX());
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line3.setStartY(points[1].getCenterY());
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line3.setEndX(points[2].getCenterX());
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line3.setEndY(points[2].getCenterY());
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// Compute angles
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double a = new Point2D(points[2].getCenterX(), points[2].getCenterY()).
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distance(points[1].getCenterX(), points[1].getCenterY());
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double b = new Point2D(points[2].getCenterX(), points[2].getCenterY()).
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distance(points[0].getCenterX(), points[0].getCenterY());
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double c = new Point2D(points[1].getCenterX(), points[1].getCenterY()).
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distance(points[0].getCenterX(), points[0].getCenterY());
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double[] angle = new double[3];
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angle[0] = Math.acos((a * a - b * b - c * c) / (-2 * b * c));
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angle[1] = Math.acos((b * b - a * a - c * c) / (-2 * a * c));
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angle[2] = Math.acos((c * c - b * b - a * a) / (-2 * a * b));
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for (int i = 0; i < 3; i++) {
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text[i].setX(points[i].getCenterX());
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text[i].setY(points[i].getCenterY() - radius);
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text[i].setText(String.format("%.2f", Math.toDegrees(angle[i])));
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}
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}
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}

‎ch_15/Exercise15_29.java

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package ch_15;
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import javafx.animation.KeyFrame;
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import javafx.animation.Timeline;
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import javafx.application.Application;
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import javafx.scene.Scene;
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import javafx.scene.input.KeyCode;
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import javafx.scene.layout.Pane;
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import javafx.scene.shape.Circle;
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import javafx.scene.shape.Polygon;
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import javafx.scene.shape.Rectangle;
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import javafx.stage.Stage;
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import javafx.util.Duration;
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/**
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* **15.29 (Racing car) Write a program that simulates car racing, as shown in
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* Figure 15.34a. The car moves from left to right. When it hits the right end, it
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* restarts from the left and continues the same process. You can use a timer to
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* control animation. Redraw the car with a new base coordinates (x, y), as shown
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* in Figure 15.34b. Also let the user pause/resume the animation with a
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* button press/release and increase/decrease the car speed by pressing the UP and
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* DOWN arrow keys.
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*/
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public class Exercise15_29 extends Application {
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private final double WIDTH = 600;
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private final double HEIGHT = 100;
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@Override
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public void start(Stage primaryStage) throws Exception {
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RacingPane pane = new RacingPane(WIDTH, HEIGHT);
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pane.start();
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pane.setOnMousePressed(e -> pane.pause());
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pane.setOnMouseReleased(e -> pane.play());
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pane.setOnKeyPressed(e -> {
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if (e.getCode() == KeyCode.UP) {
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pane.increaseSpeed();
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} else if (e.getCode() == KeyCode.DOWN) {
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pane.decreaseSpeed();
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}
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});
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Scene scene = new Scene(pane, WIDTH, HEIGHT);
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primaryStage.setTitle(getClass().getName());
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primaryStage.setScene(scene);
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primaryStage.show();
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pane.requestFocus();
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}
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}
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class RacingPane extends Pane {
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private double x;
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private double y;
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private CarShape car;
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private Timeline animation;
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/**
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* Construct and animate a default CarPane
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*/
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RacingPane(double width, double height) {
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setHeight(height);
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setWidth(width);
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car = new CarShape(x, y, 5, this);
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x = 0;
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y = 100;
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animation = new Timeline(
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new KeyFrame(Duration.millis(50), e -> car.moveCar(x, y, this)));
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animation.setCycleCount(Timeline.INDEFINITE);
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}
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void start() {
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animation.play();
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}
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/**
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* Pause animation
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*/
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public void pause() {
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animation.pause();
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}
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/**
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* Play animation
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*/
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public void play() {
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animation.play();
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}
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/**
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* Increase rate by 1
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*/
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public void increaseSpeed() {
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animation.setRate(animation.getRate() + 1);
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}
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/**
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* decrease rate by 1
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*/
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public void decreaseSpeed() {
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animation.setRate(animation.getRate() > 0 ? animation.getRate() - 1 : 0);
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}
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class CarShape {
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private double wheelRadius;
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private Rectangle lowerBody;
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private Polygon topBody;
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private Circle wheel1;
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private Circle wheel2;
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public CarShape(double x, double y, double wheelRadius, Pane pane) {
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this.wheelRadius = wheelRadius;
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drawAndRender(x, y, pane);
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}
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void drawAndRender(double x, double y, Pane pane) {
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if (!pane.getChildren().isEmpty()) {
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pane.getChildren().clear();
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}
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lowerBody = new Rectangle(x, y - 20, 50, 10);
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topBody = new Polygon(x + 10, y - 20, x + 20, y - 30, x + 30,
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y - 30, x + 40, y - 20);
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wheel1 = new Circle(x + 15, y - 5, wheelRadius);
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wheel2 = new Circle(x + 35, y - 5, wheelRadius);
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pane.getChildren().addAll(getLowerBody(), getWheel1(), getWheel2(), getTopBody());
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}
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/**
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* Calculate new x position and draw car
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*
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* @param x the current x position
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* @param y the current y position
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* @param pane the pane to render the car on
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*/
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protected void moveCar(double x, double y, Pane pane) {
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x += 1;
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drawAndRender(x, y, pane);
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}
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public Rectangle getLowerBody() {
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return lowerBody;
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}
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public Polygon getTopBody() {
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return topBody;
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}
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public Circle getWheel1() {
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return wheel1;
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}
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public Circle getWheel2() {
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return wheel2;
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}
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}
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}

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