JavaFX、合并碰撞的弹球

package collection;
 
import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.application.Application;
import javafx.beans.property.DoubleProperty;
import javafx.geometry.Point2D;
import javafx.geometry.Pos;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ScrollBar;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.paint.Paint;
import javafx.scene.shape.Circle;
import javafx.stage.Stage;
import javafx.util.Duration;
 
import java.security.SecureRandom;
import java.util.ConcurrentModificationException;
 
public class MultipleBouncePane extends Application {
    @Override
    public void start(Stage primaryStage) throws Exception {
        MultipleBallPane ballPane = new MultipleBallPane(); //创建多球面板
        ballPane.setStyle("-fx-border-color: darkseagreen;");
 
        Button suspend = new Button("Suspend"); //按钮
        Button resume = new Button("Resume");
        Button add = new Button("+");
        Button subtract = new Button("-");
        HBox hBox = new HBox(10, suspend, resume, add, subtract);
        hBox.setAlignment(Pos.CENTER);
 
        suspend.setOnAction(event -> ballPane.pause()); //按钮注册动作事件
        resume.setOnAction(event -> ballPane.play());
        add.setOnAction(event -> ballPane.add());
        subtract.setOnAction(event -> ballPane.subtract());
 
        ballPane.setOnMousePressed(event -> ballPane.pause());  //多球面板注册鼠标按下事件
        ballPane.setOnMouseReleased(event -> ballPane.play());
 
        ScrollBar speed = new ScrollBar();  //滚动条
        speed.setMax(20);   //设置最大值
        speed.setValue(10); //设置值
        ballPane.rateProperty().bind(speed.valueProperty());    //多球面板速度属性绑定滚动条值属性
 
        BorderPane pane = new BorderPane(ballPane); //总面板
        pane.setTop(speed);
        pane.setBottom(hBox);
 
        Scene scene = new Scene(pane, 350, 250);
        primaryStage.setScene(scene);
        primaryStage.setTitle("MultipleBouncePane");
        primaryStage.show();
    }
 
    /** 内部类（多球面板） */
    private class MultipleBallPane extends Pane {
        private Timeline animation; //时间线动画
 
        public MultipleBallPane() {
            animation = new Timeline(new KeyFrame(Duration.millis(50), event -> moveBall()));
            animation.setCycleCount(Timeline.INDEFINITE);
            animation.play();
        }
 
        /** 添加弹球 */
        public void add() {
            Color color = new Color(Math.random(), Math.random(), Math.random(), 0.5);  //创建半透明的随机颜色对象
            Ball ball = new Ball(30, 30, 2+new SecureRandom().nextInt(19), color);  //创建弹球对象
            getChildren().add(ball);    //多球面板添加弹球
 
            //弹球注册鼠标按下事件
            ball.setOnMousePressed(event -> {
                if (ball.isPressed()) { //如果被按下
                    animation.stop();
                    getChildren().remove(ball); //移除当前弹球
                    animation.play();
                }
            });
        }
 
        /** 减少弹球 */
        public void subtract() {
            if (getChildren().size() > 0) { //移除最大半径的弹球
                Ball temp = (Ball)getChildren().get(0);
                for (Node node: getChildren()) {
                    if (((Ball)node).getRadius() > temp.getRadius())
                        temp = (Ball)node;
                }
                getChildren().remove(temp);
            }
        }
 
        /** 播放动画 */
        public void play() {
            animation.play();
        }
 
        /** 暂停动画 */
        public void pause() {
            animation.pause();
        }
 
        /** 加速动画 */
        public void increaseSpeed() {
            animation.setRate(animation.getRate() + 0.1);
        }
 
        /** 减速动画 */
        public void decreaseSpeed() {
            animation.setRate(animation.getRate() <= 0 ? 0 : animation.getRate()-0.1);
        }
 
        /** 返回动画速度属性 */
        public DoubleProperty rateProperty() {
            return animation.rateProperty();
        }
 
        /** 移动弹球 */
        protected void moveBall() {
            try {
                for (Node node : this.getChildren()) {  //遍历弹球列表
                    Ball ball = (Ball)node;
 
                    //到达边界时改变方向
                    if (ball.getCenterX() < ball.getRadius() || ball.getCenterX() > getWidth()-ball.getRadius())
                        ball.dx *= -1;
                    if (ball.getCenterY() < ball.getRadius() || ball.getCenterY() > getHeight()-ball.getRadius())
                        ball.dy *= -1;
 
                    //设置新坐标
                    ball.setCenterX(ball.dx + ball.getCenterX());
                    ball.setCenterY(ball.dy + ball.getCenterY());
 
                    //合并弹球（在边界时弹球半径的突然增大会呈水平或垂直方向（拉伸场景可解决））
                    for (Node node1: this.getChildren()) {  //再次遍历列表
                        Ball ball1 = (Ball)node1;
 
                        //如果俩球不相等且相交
                        if (!ball1.equals(ball) && (new Point2D(ball.getCenterX(), ball.getCenterY()).distance(ball1.getCenterX(),
                                ball1.getCenterY()) <= ball.getRadius()+ball1.getRadius())) {
                            int index1 = getChildren().indexOf(ball);   //获取弹球下标
                            int index2 = getChildren().indexOf(ball1);
 
                            //移除后面的球
                            if (index1 < index2) {
                                ball.setRadius(ball.getRadius() + ball1.getRadius());
                                getChildren().remove(ball1);
                            } else {
                                ball1.setRadius(ball1.getRadius() + ball.getRadius());
                                getChildren().remove(ball);
                            }
                        }
                    }
                }
            } catch (ConcurrentModificationException ex) {  //捕获并发修改异常
            }
        }
 
    }
 
    /** 内部类（弹球类） */
    class Ball extends Circle {
        private double dx = 1, dy = 1;
 
        public Ball(double centerX, double centerY, double radius, Paint fill) {
            super(centerX, centerY, radius, fill);
        }
    }
}