弹跳球在Java[关闭]

Question

我正在创建一个弹跳球项目，每次点击鼠标时，都会以随机的速度、随机的大小和随机的位置生成弹跳球，除了一件事，一切都很完美，当球从顶部和左侧撞击墙壁时，它会完全反弹，但是当球撞击窗户的底部和右侧时，它们也会反弹，但不是完全反弹，我的意思是，球在撞击墙壁之前会从窗户的右侧反弹，当球超过窗户的一半时，会从底部反弹。问题是什么，为什么要这样做？

下面是代码：

import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
//To generate random colors
/*new Color((int) Math.floor((Math.random() * 256)),(int) Math.floor((Math.random() * 256)),(int) 
Math.floor((Math.random() * 256)))*/
public class bouncingBalls {
public static void main(String[] args) {
    Program program = new Program();
    program.run();
}
}

class Program {
protected JFrame mainFrame;
protected DrawPanel drawPanel;
protected java.util.List<Ball> balls;
void run() {

    balls = new ArrayList<>();
    mainFrame = new JFrame();
    drawPanel = new DrawPanel();
    mainFrame.getContentPane().add(drawPanel);
    mainFrame.setTitle("Bouncing Balls");
    mainFrame.setSize(640, 480);
    mainFrame.setVisible(true);
    mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    /* Generate balls */
    mainFrame.addMouseListener(new MouseAdapter() {
        public void mouseClicked(MouseEvent me) {
            System.out.println("Mouse clicked");
            Ball ball = new Ball(
                    /* Random positions from 0 to windowWidth or windowHeight */
                    (int) Math.floor(Math.random() * 640),
                    (int) Math.floor(Math.random() * 480),
                    /* Random size from 10 to 30 */
                    (int) Math.floor(Math.random() * 20) + 10,
                    /* Random RGB colors*/
                    new Color(0x851E3E),
                    /* Random velocities from -5 to 5 */
                    (int) Math.floor((Math.random() * 10) - 5),
                    (int) Math.floor((Math.random() * 10) - 5)
            );

            balls.add(ball);
        }
    });
    while (true) {
        for (Ball b: balls) {
            b.update();
        }

        /* Give Swing 10 milliseconds to see the update! */
        try {
            Thread.sleep(30);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        mainFrame.repaint();
    }
}

class DrawPanel extends JPanel {
    @Override
    public void paintComponent(Graphics graphics) {
        super.paintComponent(graphics);

        for (Ball b: balls) {
            b.draw(graphics);
        }

    }
}

class Ball {
    private int posX, posY, size;
    private Color color;

    private int vx;
    private int vy;

    public Ball(int posX, int posY, int size, Color color, int vx, int vy) {
        this.posX = posX;
        this.posY = posY;
        this.size = size;
        this.color = color;
        this.vx = vx;
        this.vy = vy;
    }

    void update() {

        if (posX > mainFrame.getWidth()-size*2 || posX < 0) {
            vx *= -1;
        }

        if (posY > mainFrame.getHeight()-size-32 || posY < 0) {
            vy *= -1;
        }

        if (posX > mainFrame.getWidth()-size*2) {
            posX = mainFrame.getWidth()-size*2;
        }

        if (posX < 0) {
            posX = 0;
        }

        if (posY > mainFrame.getHeight()-size-32) {
            posY = mainFrame.getHeight()-size-32;
        }

        if (posY < 0) {
            posY = 0;
        }

        this.posX += vx;
        this.posY += vy;

    }

    void draw(Graphics g) {
        g.setColor(color);
        g.fillOval(posX, posY, size, size);
        g.getClipBounds();
        g.getClipBounds();
    }
}
}

Answer 1

好的，所以你有一些关键问题。

一个JFrame包含一个ContentPane和装饰。装饰出现在框架的边界内，这使得ContentPane的大小等于框架大小减去装饰插页。这是您遇到问题的主要原因，因为您使用框架大小而不是DrawPanel大小来确定冲突检测。

相反，您应该使用绘图面板s大小（已添加到内容窗格）。

你看我怎么能把它放在中间？更多细节。

这是一个重新构建的代码示例，它使用SwingTimer而不是Thread，因此它是线程安全的，并将主工作负载放置到DrawPanel中，而不是将其分散到所有地方。

有关更多详细信息，请参见如何使用Swing定时器

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                Program program = new Program();
                program.run();
            }
        });
    }

    class Program {

        protected JFrame mainFrame;
        protected DrawPanel drawPanel;

        void run() {

            mainFrame = new JFrame();
            drawPanel = new DrawPanel();
            mainFrame.getContentPane().add(drawPanel);
            mainFrame.setTitle("Bouncing Balls");
            mainFrame.pack();
            mainFrame.setVisible(true);
            mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        }

        class DrawPanel extends JPanel {

            private java.util.List<Ball> balls;
            private Timer timer;

            public DrawPanel() {
                balls = new ArrayList<>(25);
                addMouseListener(new MouseAdapter() {
                    public void mouseClicked(MouseEvent me) {
                        System.out.println("Mouse clicked");
                        Ball ball = new Ball(
                                /* Random positions from 0 to windowWidth or windowHeight */
                                (int) Math.floor(Math.random() * 640),
                                (int) Math.floor(Math.random() * 480),
                                /* Random size from 10 to 30 */
                                (int) Math.floor(Math.random() * 20) + 10,
                                /* Random RGB colors*/
                                Color.RED,
                                /* Random velocities from -5 to 5 */
                                (int) Math.floor((Math.random() * 10) - 5),
                                (int) Math.floor((Math.random() * 10) - 5)
                        );

                        balls.add(ball);
                    }
                });
            }

            @Override
            public void addNotify() {
                super.addNotify();
                if (timer != null) {
                    timer.stop();
                }

                timer = new Timer(30, new ActionListener() {
                    @Override
                    public void actionPerformed(ActionEvent arg0) {
                        for (Ball b : balls) {
                            b.update(getSize());
                        }
                        repaint();
                    }
                });
                timer.start();
            }

            @Override
            public void removeNotify() {
                super.removeNotify();
                if (timer == null) {
                    return;
                }
                timer.stop();
            }

            @Override
            public Dimension getPreferredSize() {
                return new Dimension(640, 480);
            }

            @Override
            public void paintComponent(Graphics graphics) {
                super.paintComponent(graphics);

                for (Ball b : balls) {
                    b.draw(graphics);
                }

            }
        }

        class Ball {

            private int posX, posY, size;
            private Color color;

            private int vx;
            private int vy;

            public Ball(int posX, int posY, int size, Color color, int vx, int vy) {
                this.posX = posX;
                this.posY = posY;
                this.size = size;
                this.color = color;
                this.vx = vx;
                this.vy = vy;
            }

            void update(Dimension bounds) {

                if (posX + size > bounds.width || posX < 0) {
                    vx *= -1;
                }

                if (posY + size > bounds.height || posY < 0) {
                    vy *= -1;
                }

                if (posX + size > bounds.width) {
                    posX = bounds.width - size;
                }

                if (posX < 0) {
                    posX = 0;
                }

                if (posY + size > bounds.height) {
                    posY = bounds.height - size;
                }

                if (posY < 0) {
                    posY = 0;
                }

                this.posX += vx;
                this.posY += vy;

            }

            void draw(Graphics g) {
                g.setColor(color);
                g.fillOval(posX, posY, size, size);
            }
        }
    }
}