Question

我正在尝试使用两个球精灵创建球碰撞。当一个球碰撞时它的速度应该取决于其他球的初始速度，所以在精灵中我需要调用另一个球的速度，但我无法弄清楚如何通过非静态变量信息。这是带错误的行

xa = BIGBALLspeedx()*(BIGBALLmass()-1)+(BallTest.ball.BALLspeedx()*2*1);

这是我的一个精灵和主要包'BallTest'的代码：

package balltest;

import java.awt.Graphics2D;
import java.awt.Rectangle;
import static java.lang.Math.sqrt;

public class BigBall {

    private final int DIAMETER = 80;
    int x = (int )(Math.random() * 200 + 15 );
    int y = (int )(Math.random() * 200 + 15 );
    int xa = (int )(Math.random() * 4  );
    int ya = (int )(1 );

    private BallTest game;

    public BigBall(BallTest game) {
        this.game= game;
    }

    public void  move() {
        if (x + xa < 0)
            xa = 1;
        if (x + xa > game.getWidth() - DIAMETER)
            xa = -1;
        if (y + ya < 0)
            ya = 1;
        if (y + ya > game.getHeight() - DIAMETER)
            ya=-1;
        if (y + ya < 1)
            ya=1;
        if (50>sqrt(xDIFF()*xDIFF()+yDIFF()*yDIFF()) && -50<sqrt(xDIFF()*xDIFF()+yDIFF()*yDIFF())) {
            xa = BIGBALLspeedx()*(BIGBALLmass()-1)+(BallTest.ball.BALLspeedx()*2*1);
        }
        x = x + xa;
        y = y + ya;
    }

    public int BIGBALLx() {
        return x+40;
    }

    public int BIGBALLy(){
        return y+40;
    }

    public int BIGBALLspeedx(){
        return xa;
    }

    public int BIGBALLspeedy(){
        return ya;
    }

    public int BIGBALLmass(){
        return 5;
    }

    public int xDIFF(){
        return game.ball.BALLx()-game.BigBall.BIGBALLx();
    }

    public int yDIFF(){
        return game.ball.BALLy()-game.BigBall.BIGBALLy();
    }

    public void paint2(Graphics2D g) {
        g.fillOval(x, y, DIAMETER, DIAMETER);
    }

    public Rectangle getBounds() {
        return new Rectangle(x, y, DIAMETER, DIAMETER);
    }
}

这是BallTest代码：

package balltest;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import static java.awt.image.ImageObserver.ABORT;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;

/**
 *
         * @author F27834
 */
public class BallTest extends JPanel {

    Ball ball = new Ball(this);
    BigBall BigBall = new BigBall(this);

    private void move() {
        ball.move();
        BigBall.move();
    }

    @Override
    public void paint(Graphics g) {
        super.paint(g);
        g.setColor(Color.RED);
        Graphics2D g2d = (Graphics2D) g;
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
            RenderingHints.VALUE_ANTIALIAS_ON);

        ball.paint(g2d);

        g.setColor(Color.BLUE);
        Graphics2D g3d = (Graphics2D) g;
        BigBall.paint2(g3d);
    }

    public void gameOver() {
        JOptionPane.showMessageDialog(this, "Game Over", "Game Over", JOptionPane.YES_NO_OPTION);
        System.exit(ABORT);
    }

    public static void main(String[] args) throws InterruptedException {
        JFrame frame = new JFrame("Mini Tennis");
        BallTest game = new BallTest();
        frame.add(game);
        frame.setSize(300, 400);
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        while (true) {
            game.move();
            game.repaint();
            Thread.sleep(10);
        }
    }
}

Answer 1

您正在尝试引用BallTest.ball - BallTest可能是另一个类，而ball是该类中定义的实例变量。在Java术语中，BallTest是一个静态引用（它指的是一个类，而不是一个对象），而ball只是由BallTest的一个实例定义。

在代码的其他部分，您可以参考game.ball。没有看到剩下的代码就无法确定，但是你应该使用game.ball而不是BallTest.ball吗？

那就是这样吗？

xa = BIGBALLspeedx()*(BIGBALLmass()-1)+(game.ball.BALLspeedx()*2*1);

Java非静态变量

1 个答案: