我必须检测javaFX程序中两个“球”何时碰撞。每次单击按钮时，都会将新的球添加到窗格中。我知道getChildren（）返回一个可观察的列表，其中包含每个球的节点，并且当我打印带有两个圆圈的列表时，例如，
Circle [centerX = 30.0，centerY = 30.0，半径= 20.0，填充= 0x9ac26780]，Circle [centerX = 224.0，centerY = 92.0，半径= 20.0，填充= 0x9ac26780]
我的想法是使用嵌套循环将每个球的（x，y）坐标与其他每个球进行比较。如何比较每个Circle的centerX和centerY以进行比较？
我尝试了getChildren（）。sublist（0,0）;认为我将获得第一个元素的centerX值，但这不起作用。我也尝试过getCenterX，因为Ball扩展了Circle，但这也失败了。谢谢你的时间。
public class Exercise20_05 extends Application {
@Override // Override the start method in the Application class
public void start(Stage primaryStage) {
MultipleBallPane ballPane = new MultipleBallPane();
ballPane.setStyle("-fx-border-color: yellow");
Button btAdd = new Button("+");
Button btSubtract = new Button("-");
HBox hBox = new HBox(10);
hBox.getChildren().addAll(btAdd, btSubtract);
hBox.setAlignment(Pos.CENTER);
// Add or remove a ball
btAdd.setOnAction(e -> ballPane.add());
btSubtract.setOnAction(e -> ballPane.subtract());
// Pause and resume animation
ballPane.setOnMousePressed(e -> ballPane.pause());
ballPane.setOnMouseReleased(e -> ballPane.play());
// Use a scroll bar to control animation speed
ScrollBar sbSpeed = new ScrollBar();
sbSpeed.setMax(20);
sbSpeed.setValue(10);
ballPane.rateProperty().bind(sbSpeed.valueProperty());
BorderPane pane = new BorderPane();
pane.setCenter(ballPane);
pane.setTop(sbSpeed);
pane.setBottom(hBox);
// Create a scene and place the pane in the stage
Scene scene = new Scene(pane, 250, 150);
primaryStage.setTitle("MultipleBounceBall"); // Set the stage title
primaryStage.setScene(scene); // Place the scene in the stage
primaryStage.show(); // Display the stage
}
private class MultipleBallPane extends Pane {
private Timeline animation;
public MultipleBallPane() {
// Create an animation for moving the ball
animation = new Timeline(
new KeyFrame(Duration.millis(50), e -> moveBall()));
animation.setCycleCount(Timeline.INDEFINITE); //animation will play indefinitely
animation.play(); // Start animation
}
public void add() {
Color color = new Color(Math.random(),
Math.random(), Math.random(), 0.5);
//creates a new Ball at (30, 30) with a radius of 20
getChildren().add(new Ball(30, 30, 20, color));
ballCollision();
}
public void subtract() {
if (getChildren().size() > 0) {
getChildren().remove(getChildren().size() - 1);
}
}
public void play() {
animation.play();
}
public void pause() {
animation.pause();
}
public void increaseSpeed() {
animation.setRate(animation.getRate() + 0.1);
}
public void decreaseSpeed() {
animation.setRate(
animation.getRate() > 0 ? animation.getRate() - 0.1 : 0);
}
public DoubleProperty rateProperty() {
return animation.rateProperty();
}
protected void moveBall() {
for (Node node: this.getChildren()) {
Ball ball = (Ball)node;
// Check boundaries
if (ball.getCenterX() < ball.getRadius() ||
ball.getCenterX() > getWidth() - ball.getRadius()) {
ball.dx *= -1; // Change ball move direction
}
if (ball.getCenterY() < ball.getRadius() ||
ball.getCenterY() > getHeight() - ball.getRadius()) {
ball.dy *= -1; // Change ball move direction
}
// Adjust ball position
ball.setCenterX(ball.dx + ball.getCenterX());
ball.setCenterY(ball.dy + ball.getCenterY());
ballCollision();
}
}
//check for ball collisions
protected void ballCollision() {
/*System.out.println(getChildren().size());
getChildren returns an observableList; this observableList is what
keeps track of the balls (specifically, the nodes added to ballPane)
added each time the + button is clicked
*/
ObservableList ballList = getChildren();
System.out.println(ballList.get(0));
//if there are 2 or more balls, check for collision
if (ballList.size() > 1) {
//compare each (x,y) coordinate value to every other (x,y) value
for (int i = 0; i < ballList.size(); i++) {
for (int k = 0; k < ballList.size(); k++) {
// if (ballList.sublist(i,i) < 1) {
//
// }
}
}
}
}
}
class Ball extends Circle {
private double dx = 1, dy = 1;
Ball(double x, double y, double radius, Color color) {
super(x, y, radius);
setFill(color); // Set ball color
}
}
/**
* The main method is only needed for the IDE with limited
* JavaFX support. Not needed for running from the command line.
*/
public static void main(String[] args) {
launch(args);
}
}
编辑：多亏了几个人，我才能够使碰撞检查正常工作。一个球将被移除，但是我得到了ConcurrentModificationException。这是更新的方法：
protected void ballCollision() {
ObservableList ballList = getChildren();
//if there are 2 or more balls, check for collision
if (ballList.size() > 1) {
//compare each (x,y) coordinate value to every other (x,y) value
for (int i = 0; i < ballList.size(); i++) {
for (int k = i + 1; k < ballList.size(); k++) {
Circle c1 = (Circle) ballList.get(i);
Circle c2 = (Circle) ballList.get(k);
if ((c1.getCenterX() <= c2.getCenterX() * 1.10 &&
(c1.getCenterX() >= c2.getCenterX()*.90)) &&
((c1.getCenterY() <= c2.getCenterY() * 1.10) &&
c1.getCenterY() >= c2.getCenterY() * .90)){
ballList.remove(c2);
}
}
}
}
}
最终编辑：感谢David Wallace花时间帮助我。问题是我在moveBall方法的for-each循环内调用ballCollision。一旦我将其移出循环，它就会完美运行。
最佳答案
您可以像对待其他ObservableList一样对待List。您可能想要将元素强制转换为正确的类，如此处所示。使用hypot类的Math方法计算中心之间的距离。
for (int first = 0; first < ballList.size(); first++) {
Ball firstBall = (Ball) ballList.get(first);
for (int second = first + 1; second < ballList.size(); second++) {
Ball secondBall = (Ball) ballList.get(second);
double distanceBetweenCentres = Math.hypot(
firstBall.getCenterX() - secondBall.getCenterX(),
firstBall.getCenterY() - secondBall.getCenterY());
if (distanceBetweenCentres <= firstBall.getRadius() + secondBall.getRadius()) {
System.out.println("Collision between ball " + first + " and ball " + second);
}
}
}
关于java - 当getChildren()返回以Circle作为第一个元素的可观察列表时，如何访问Circle中的值？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/41918076/