Question

我正在制作一个java应用程序（用于练习），其中必须有一个面板和2个按钮。

每按一次开始按钮，必须显示一个球，并根据线程移动。用户可以一直显示最多10个独立球。
按下停止按钮，每按一次停止按钮，必须移除1个球（例如，当有4个球时，用户必须按4次停止按钮才能独立移除所有球）
球的所有x和y坐标必须存储在矩阵
当一个或多个球相互碰撞时，只有碰撞的球必须从红色变为蓝色

好的，我几乎完全完成了它（从第1点到第4点），但问题就出现了。当一个球与另一个球相撞时，我的代码将所有球颜色从红色变为蓝色，而不是将碰撞球的颜色改为蓝色。我知道我的错误在于new Balls().setColor(Color.Blue)，但我不知道如何只改变碰撞球。

下面是java应用程序和代码的屏幕截图。任何人都可以帮我解决这个问题吗？

Printscreen：

源代码：

import java.awt.Color;             
import java.awt.Dimension;    
import java.awt.FlowLayout;   
import java.awt.Graphics;    
import java.awt.event.ActionEvent;   
import java.awt.event.ActionListener;   
import java.util.ArrayList;  
import java.util.List;  
import javax.swing.JButton;    
import javax.swing.JFrame;    
import javax.swing.JLabel;  
import javax.swing.JPanel;`


public class BouncingBalls extends JPanel implements ActionListener {

protected List<Ball> balls = new ArrayList<Ball>(10);
private final Container container;
private final DrawCanvas canvas;
private  int canvasWidth;
private  int canvasHeight;
public JButton start, stop;
int [][] coords= new int[11][2];
int ammountOfBalls = 0;
static Color clr= Color.RED;


public static int random(int maxRange) {
    return (int) Math.round((Math.random() * maxRange));
}

public BouncingBalls(int width, int height) {
    setLayout(new FlowLayout());
     start= new JButton("start");
    start.addActionListener(this);
     stop= new JButton("stop");
    stop.addActionListener(this);
    add(start);
    add(stop);
    add(new JLabel(""));
    container = new Container();
    canvasWidth = width;
    canvasHeight = height;
    canvas = new DrawCanvas();
    this.setLayout(new FlowLayout());
    this.add(canvas);
    start();

}

public void start() {

    Thread t = new Thread() {
        @Override
        public void run() {

            while (true) {

                update();
                getPositions();
                collisionDetection();
                repaint();
                try {
                    Thread.sleep(30);
                } catch (InterruptedException e) {
                }
            }
        }

        private void collisionDetection() {
            // The algorithm  that detects collision
          for(int i=0;i<ammountOfBalls;i++){
            for(int j=i+1; j<ammountOfBalls; j++){
                  if(collisionMethod(i,j)){  // my collision method
                      //HOW DO I CHANGE ONLY THE COLLIDING BALLS COLOR HERE????
                     new Ball().setColor(Color.BLUE);  // this line here changes the color of all the balls on the panel
                      System.out.println("Its a hit");
                  }
              }

           }  

        }

        private void getPositions() {
            int row=0;
            for (Ball ball : balls) {
             int x =ball.getXPosition();
             int y =ball.getYPosition();
             coords[row][0]=x;
             coords[row][1]=y;
             row++;
            }

        }

        private boolean collisionMethod(int i, int j) {
           float xd = coords[i][0]-coords[j][0];
           float yd=coords[i][1]-coords[j][1];
           float radius= new Ball().ballRadius;
           float sqrRadius= radius * radius;
           float distSqr= (xd * xd) + (yd * yd);

           if(distSqr <= sqrRadius)
               return true;

            return false;
        }
      };
    t.start();
}

public void update() {
    for (Ball ball : balls) {
        ball.move(container);
    }
 }

@Override
public void actionPerformed(ActionEvent e) {
    if(e.getSource() == start){
        if(ammountOfBalls < 10){
            // to limit the ammount of balls to 10
            balls.add(new Ball());
            ammountOfBalls++;
       }
    }

    else if( e.getSource() == stop){
        if(ammountOfBalls > 0){
      ammountOfBalls --;
      balls.remove(ammountOfBalls);

    }

    }
}

class DrawCanvas extends JPanel {

    @Override
    public void paintComponent(Graphics g) {

        super.paintComponent(g);
        container.draw(g);
        for (Ball ball : balls) {
            ball.draw(g);
        }
    }
    @Override
    public Dimension getPreferredSize() {
        return (new Dimension(700, 400));
    }
}

public static void main(String[] args) {
            JFrame f = new JFrame("Bouncing Balls");
            f.setDefaultCloseOperation(f.EXIT_ON_CLOSE);
            f.setPreferredSize(new Dimension(800,500));
            f.setContentPane(new BouncingBalls(800,800));
            f.pack();
            f.setVisible(true);
    }


public static class Ball {

    public int random(int maxRange) {
        return (int) Math.round(Math.random() * maxRange);
    }

int x = random(700); // method to get random coords for the x-value
int y = random(400); // method to get random coords for the y-value  ...... these are used to get random positions for the balls instead of only static
int xMovement = 10;
int yMovement = 10;
int ballRadius = 20;
int i = 0;


public Color getColor(){
  return clr;
}
public Color setColor(Color color){
clr=color;
return clr;
}
    public void draw(Graphics g) {
        g.setColor(getColor());
        g.fillOval(x,y,ballRadius,ballRadius);

    }
    public int getXPosition(){
        return x;
    }
    public int getYPosition(){
        return y;
    }

    public void move(Container container) {
        x += xMovement;
        y += yMovement;

        if (x - ballRadius < 0) {
            xMovement = -xMovement;
            x = ballRadius;
        } 
        else if (x + ballRadius > 700) {
            xMovement = -xMovement;
            x = 700 - ballRadius;
        }

        if (y - ballRadius < 0) {
            yMovement = -yMovement;
            y = ballRadius;
        } 
        else if (y + ballRadius > 400) {
            yMovement = -yMovement;
            y = 400 - ballRadius;
        }
    }
}



public static class Container {
    private static final int hightPanel = 800;
    private static final int widthPanel=  800;

    public void draw(Graphics g) {
        g.setColor(Color.WHITE);
        g.fillRect(0, 0, widthPanel, hightPanel);
    }
}
}

`

Answer 1

您已将clr定义为应用程序的静态字段。当您的Ball课程调用setColor()时，您要将clr的值更改为蓝色...然后调用Ball的任何getColor()都会看到clr 1}}是蓝色的。

解决方案：不要让clr成为应用程序范围内的静态字段。在Ball类中将其定义为非静态字段，因此每个Ball都有自己的颜色。

碰撞时改变球的颜色

1 个答案: