java线程弹跳球

Question

提前感谢帮助我创建了一个程序，使多个弹跳球当用户点击屏幕上一个新的球应该出现并在屏幕上移动。但是当我点击屏幕上一个球出现，根本不移动。当另一个点击发生时，以前创建的球立即跳到另一个位置。

这是ball类：用于创建球

import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.geom.Ellipse2D;
import java.util.Random;
import javax.swing.JComponent;

public class Ball extends JComponent implements Runnable{
    private final int DIAMETER = 25;
    private final int v1 = 5;
    private final int v2 = -5;
    private final Random rnd = new Random();
    private int posX;
    private int posY;
    private Color color;
    private int xVelocity;
    private int yVelocity;
    
    public Ball(int posX, int posY) {
        this.posX = posX;
        this.posY = posY;
        this.color = randomColor(); 
        this.xVelocity = rnd.nextBoolean()?v1:v2;
        this.yVelocity = rnd.nextBoolean()?v1:v2;
    }
    
    public void move() {
        if (posX < 15) {
            xVelocity = -xVelocity;
        } else if(posX > 475) {
            xVelocity = -xVelocity;
        }
        
        if (posY < 0) {
            yVelocity = -yVelocity;
        } else if(posY > 475) {
            yVelocity = -yVelocity;
        }
        posX +=xVelocity;
        posY +=yVelocity;

    }
    
    public void draw(Graphics2D g2) {
        g2.setColor(color);
        g2.fill(new Ellipse2D.Double(posX,posY,DIAMETER,DIAMETER));
    }
    
    private static Color randomColor() {
        int r = (int)(Math.random()*255);
        int g = (int)(Math.random()*255);
        int b = (int)(Math.random()*255);
        Color rColor = new Color(r,g,b);
        return rColor;
    }

    @Override
    public void run() {
            while(!Thread.interrupted()) {
            move();
            repaint();
            try {
                Thread.sleep(60);
            } catch (InterruptedException ex) {}
            }

        
    }
}

这是一个ball组件类：用于创建面板

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class BallComponent extends JPanel{
    private ArrayList<Ball> bList;
    
    public BallComponent() {
        bList = new ArrayList<Ball>();
        this.setPreferredSize(new Dimension(500,500));
        this.setBackground(Color.BLACK);
        this.addMouseListener(new ClickListener());
    }
    
    public void paintComponent(Graphics g) {
        Graphics2D g2 = (Graphics2D)g;
        super.paintComponent(g2);
        for (Ball a : bList) {
            a.draw(g2);
        }
    }
    
    private class ClickListener extends MouseAdapter{
        public void mouseClicked(MouseEvent e) {
            Ball a = new Ball(e.getX(),e.getY());
            bList.add(a);
            repaint();
            Thread gameThread = new Thread(a);
            gameThread.start();
        }
    }
    
    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.setTitle("Bouncing Balls");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(new BallComponent());
        frame.pack();
        frame.setVisible(true);
    }
}

Answer 1

因为你有一堆线程在做随机的事情。你不妨让你的JPanel更新自己。

在你的主要方法的末尾。

new Thread( ()->{
    while(true){
        frame.repaint();
        try{
            Thread.sleep(60);
        } catch(Exception e){
            break;
        }
    }
}).start();

通常你会用一个定时器任务来完成这个任务，但既然你说你不能用定时器，我就写了一个线程版本。

我认为repaint（）可以安全地从关闭EDT调用，因为它只是计划重新绘制。paintComponent方法和click方法将仅在EDT上调用。所以你不应该得到CCME。多线程有很多比赛条件，但唯一的问题似乎是球被拉离了位置。