我想在Java中做一个弹跳球应用程序。每个球都应通过鼠标单击来发生，并且每个球都应具有随机的速度，颜色，半径和起始位置。除了鼠标侦听器发生的部分，我设法完成了所有操作。无论我在mousePressed方法中做什么都没有用。我应该怎么做才能使用户按下鼠标时创建随机球？
编辑：这是我的代码的最新版本。现在的问题是我不能制造多个球。当我在屏幕上单击时，同一个球就一直在加速。
弹跳球类
public class BouncingBalls extends JPanel implements MouseListener{
private Ball ball;
protected List<Ball> balls = new ArrayList<Ball>(20);
private Container container;
private DrawCanvas canvas;
private int canvasWidth;
private int canvasHeight;
public static final int UPDATE_RATE = 30;
int x = random(480);
int y = random(480);
int speedX = random(30);
int speedY = random(30);
int radius = random(20);
int red = random(255);
int green = random(255);
int blue = random(255);
int count = 0;
public static int random(int maxRange) {
return (int) Math.round((Math.random() * maxRange));
}
public BouncingBalls(int width, int height){
canvasWidth = width;
canvasHeight = height;
ball = new Ball(x, y, speedX, speedY, radius, red, green, blue);
container = new Container();
canvas = new DrawCanvas();
this.setLayout(new BorderLayout());
this.add(canvas, BorderLayout.CENTER);
this.addMouseListener(this);
}
public void start(){
Thread t = new Thread(){
public void run(){
while(true){
update();
repaint();
try {
Thread.sleep(1000 / UPDATE_RATE);
} catch (InterruptedException e) {}
}
}
};
t.start();
}
public void update(){
ball.move(container);
}
class DrawCanvas extends JPanel{
public void paintComponent(Graphics g){
super.paintComponent(g);
container.draw(g);
ball.draw(g);
}
public Dimension getPreferredSize(){
return(new Dimension(canvasWidth, canvasHeight));
}
}
public static void main(String[] args){
javax.swing.SwingUtilities.invokeLater(new Runnable(){
public void run(){
JFrame f = new JFrame("Bouncing Balls");
f.setDefaultCloseOperation(f.EXIT_ON_CLOSE);
f.setContentPane(new BouncingBalls(500, 500));
f.pack();
f.setVisible(true);
}
});
}
@Override
public void mouseClicked(MouseEvent e) {
// TODO Auto-generated method stub
}
@Override
public void mouseEntered(MouseEvent e) {
// TODO Auto-generated method stub
}
@Override
public void mouseExited(MouseEvent e) {
// TODO Auto-generated method stub
}
@Override
public void mousePressed(MouseEvent e) {
balls.add(new Ball(x, y, speedX, speedY, radius, red, green, blue));
start();
}
@Override
public void mouseReleased(MouseEvent e) {
// TODO Auto-generated method stub
}
}
球类
import java.awt.Color;
import java.awt.Graphics;
public class Ball{
public static int random(int maxRange) {
return (int) Math.round((Math.random() * maxRange));
}
private BouncingBalls balls;
int x = random(480);
int y = random(480);
int speedX = random(30);
int speedY = random(30);
int radius = random(20);
int red = random(255);
int green = random(255);
int blue = random(255);
int i = 0;
public Ball(int x, int y, int speedX, int speedY, int radius, int red, int green, int blue){
this.x = x;
this.y = y;
this.speedX = speedX;
this.speedY = speedY;
this.radius = radius;
this.red = red;
this.green = green;
this.blue = blue;
}
public void draw(Graphics g){
for(Ball ball : balls){
g.setColor(new Color(red, green, blue));
g.fillOval((int)(x - radius), (int)(y - radius), (int)(2 * radius), (int)(2 * radius));
}
}
public void move(Container container){
x += speedX;
y += speedY;
if(x - radius < 0){
speedX = -speedX;
x = radius;
}
else if(x + radius > 500){
speedX = -speedX;
x = 500 - radius;
}
if(y - radius < 0){
speedY = -speedY;
y = radius;
}
else if(y + radius > 500){
speedY = -speedY;
y = 500 - radius;
}
}
}
集装箱类
import java.awt.Color;
import java.awt.Graphics;
public class Container {
private static final int HEIGHT = 500;
private static final int WIDTH = 500;
private static final Color COLOR = Color.WHITE;
public void draw(Graphics g){
g.setColor(COLOR);
g.fillRect(0, 0, WIDTH, HEIGHT);
}
}
错误：这部分代码中出现“只能迭代数组或java.lang.Iterable实例”错误：
public void draw(Graphics g){
for(Ball ball : balls){
g.setColor(new Color(red, green, blue));
g.fillOval((int)(x - radius), (int)(y - radius), (int)(2 * radius), (int)(2 * radius));
}
}
最佳答案
首先，如果要渲染多个球，则应创建另一个类来包含绘制一个球所需的所有属性（甚至可以使用draw (Graphics g)方法委托该绘制）。这样，您在BouncingBalls类上将有一个球列表，这些球应进行迭代并在paintComponent方法上进行绘制。
也就是说，您的mouseClicked处理程序将只创建一个新的Ball实例并将其添加到列表中。
编辑：
有关如何在DrawCanvas类上进行绘制的示例：
class DrawCanvas {
public void paintComponent(Graphics g){
super.paintComponent(g);
container.draw(g);
for (Ball ball : balls)
//the draw method should only care of the specific ball instance
//you are calling it from
ball.draw(g);
}
...
我认为您在将问题分成多个类并使它们的实例协作以执行所需操作时遇到问题。如果您确实对此有疑问，建议您阅读一些有关该主题的文章/书，以更好地了解类和对象的概念以及它们的工作方式。它肯定会帮助您轻松进行编程。