Question

这是我的第一个图形Java程序，我尝试做的是重新创建一个简单的经典程序，我在JFrame窗口中弹出多个球。

到目前为止，我已成功地使用run()方法内的代码获得一个球反弹。这适用于我创建的一个球对象，但现在我想要有很多球，所以我试图在我的Ball类中创建一个方法，使我创建的每个球对象在我的＆＃34;球世界＆＃34;独立地

现在我所关心的只是他们从墙上弹跳而不是彼此（我稍后会想到的）。

问题：在我的ballMove(int, int, int, int)方法中，我有四个int参数，其中前两个参数是width和height window，最后两个参数是Xspeed和Yspeed。当我浏览if statements时，当球击中右侧或底壁时，它将温和地将x和y speed参数设置为负值，但是当run()方法执行时再次ballMove(int, int, int, int)方法，他们回到积极的状态，球从窗口消失。我尝试在我的球类中使用一堆getter和setter方法。我在ballMove(int, int, int, int)方法中尝试了临时变量。我没有尝试过任何作品。

问题：通过使用我的Ball类方法，如何防止我的参数Xspeed和Yspeed重新初始化我的实例速度变量为正值球与墙壁相撞？

因为我是图形编程的新手，所以非常感谢任何有用的建议。

import java.awt.Color;
import java.awt.Graphics;
import java.util.Random;

import javax.swing.JFrame;

public class Main extends JFrame implements Runnable {
    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    private int width = 800;
    private int height= 600;
    private int ballRadius = 50;

    private Random rand = new Random();

    //Create and initialize a ball object
    public Ball ball = new Ball(Color.BLUE, ballRadius, ballRadius, rand.nextInt(500), rand.nextInt(500));
    //public Ball ball2 = new Ball(Color.RED, ballRadius, ballRadius, rand.nextInt(500), rand.nextInt(500));
    //public Ball ball3 = new Ball(Color.GREEN, ballRadius, ballRadius, rand.nextInt(500), rand.nextInt(500));
    //public Ball ball4 = new Ball(Color.ORANGE, ballRadius, ballRadius, rand.nextInt(500), rand.nextInt(500));
    //public Ball ball5 = new Ball(Color.YELLOW, ballRadius, ballRadius, rand.nextInt(500), rand.nextInt(500));
    //constructor
    public Main(){

        setSize(width, height);
        setDefaultCloseOperation(EXIT_ON_CLOSE);

    }
    //Paint the ball(s)
    public void paint(Graphics g){
        super.paint(g);
        g.setColor(ball.getColor());
        g.fillOval(ball.getBallX(), ball.getBallY(), ball.getWidth(), ball.getHeight());
        //g.setColor(ball2.getColor());
        //g.fillOval(ball2.getBallX(), ball2.getBallY(), ball2.getWidth(), ball2.getHeight());
        //g.setColor(ball3.getColor());
        //g.fillOval(ball3.getBallX(), ball3.getBallY(), ball3.getWidth(), ball3.getHeight());
        //g.setColor(ball4.getColor());
        //g.fillOval(ball4.getBallX(), ball4.getBallY(), ball4.getWidth(), ball4.getHeight());
        //g.setColor(ball5.getColor());
        //g.fillOval(ball5.getBallX(), ball5.getBallY(), ball5.getWidth(), ball5.getHeight());
    }
    //Run the program
    public static void main(String [] args){
        Main main = new Main();
        main.setVisible(true);
        main.run();

    }

    @Override
    public void run() {
        // TODO Auto-generated method stub


        while(true){
            try {
                Thread.sleep(10);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            ball.ballMove(width, height, 20, 5);
            repaint();
            //ball2.ballMove(width, height, 15, 3);
            //repaint();
            //ball3.ballMove(width, height, 3, 20);
            //repaint();
            //ball4.ballMove(width, height, 10, 10);
            //repaint();
            //ball5.ballMove(width, height, 10, 20);
            //repaint();


        }
    }


}

这是我的Ball班级

import java.awt.Color;

import javax.swing.JFrame;


public class Ball extends JFrame {
    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    private int width, height, ball_X, ball_Y;
    private int Xspeed;
    private int Yspeed;
    private Color color;
    public Ball(Color color, int width, int height, int ball_X, int ball_Y){
        this.width = width;
        this.height = height;
        this.color = color;
        this.ball_X = ball_X;
        this.ball_Y = ball_Y;
    }
    public Color getColor(){
        return this.color;
    }
    public int getWidth(){
        return this.width;
    }
    public int getHeight(){
        return this.height;
    }
    public int getBallX(){
        return this.ball_X;
    }
    public int getBallY(){
        return this.ball_Y;
    }
    public void setSpeedX(int x){
        this.Xspeed = x;
    }
    public void setSpeedY(int x){
        this.Yspeed = x;
    }
    public int getSpeedX(){
        return this.Xspeed;
    }
    public int getSpeedY(){
        return this.Yspeed;
    }
    public void setBallX(int x){
        this.ball_X = x;
    }
    public void setBallY(int y){
        this.ball_Y = y;
    }
    public void ballMove(int X, int Y, int xSpeed, int ySpeed){

        //initialize Xspeed and Yspeed with the parameters of the function
        this.setSpeedX(xSpeed);
        this.setSpeedY(ySpeed);
        //Moves the balls by adding the set speed to the position of the balls each time thread is executed
        this.setBallX(this.getBallX() + this.getSpeedX());
        this.setBallY(this.getBallY() + this.getSpeedY());
        //When the balls hit the walls they are suppose to bounce back until they hit another wall.
        if(this.getBallX() + 50 >= X){
            this.setSpeedX(-xSpeed);
        }
        if(this.getBallY() + 50 >= Y){
            this.setSpeedY(-ySpeed);
        }
        if(this.getBallX() + 25 <= 0){
            this.setBallX(xSpeed);
        }
        if(this.getBallY() + 25 <= 0){
            this.setSpeedY(ySpeed);
        }
    }
}

Answer 1

你的问题就在那里：

ball.ballMove(width, height, 20, 5);

因为这是一个循环，所以每次调用它都会让它向同一个方向移动。如果碰到墙壁，你会在转弯结束时反转速度，但这并不重要，因为下次你打电话时，球仍会朝+20，+ 5移动。

我的建议是在创建球的实例时添加速度参数，并让球更换自己的速度。

ball.ballMove(width, height);

其他建议：在实际移动球之前进行碰撞检查。这样你就可以确保在实际移动它之前没有走错方向。

现在，另一个问题是，在你的主要部分，你正在调用runnable的run()方法。 Run在当前线程上执行。你需要做这样的事情：

Thread t = new Thread(main); t.start();

独立于JFrame进行绘图和计算。

Java Graphics＆＃34; Bouncing Ball＆＃34;程序

1 个答案: