java - 我无法让蛇的 body 部位沿着头部的路径移动

Question

Board.Java(程序逻辑部分)

package snake;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.ArrayList;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Board extends JPanel implements KeyListener, Runnable{
private final int WIDTH = 500, HEIGHT = 500,TWIDTH = WIDTH/25, THEIGHT = HEIGHT/25, RAND_POS = 29;
private int foodLocX, foodLocY, snakeHeadX = 240, snakeHeadY = 240;;
private boolean running = true, up = false,down = false,left = false,right = true;
private JFrame frame;
private Thread t;
private ArrayList<BodyPart> body;
public Board() {
    frame = new JFrame("Snake");
    initBoard();
    foodLocX = snakeHeadX + 8*TWIDTH;
    foodLocY = snakeHeadY;
    body = new ArrayList<BodyPart>();
    body.add(new BodyPart(snakeHeadX,snakeHeadY, TWIDTH));
    t = new Thread(this);
}

public void initBoard() {
    frame.setPreferredSize(new Dimension(518,540));
    this.setPreferredSize(new Dimension(WIDTH,HEIGHT));
    frame.addKeyListener(this);
    frame.pack();
    frame.add(this);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setVisible(true);
}

private void locateApple() {

    int r = (int) (Math.random() * RAND_POS);
    foodLocX = ((r * TWIDTH));

    r = (int) (Math.random() * RAND_POS);
    foodLocY = ((r * THEIGHT));

    while(foodLocX >= WIDTH || foodLocY >= HEIGHT || foodLocX < 0 || foodLocY < 0) {
         r = (int) (Math.random() * RAND_POS);
         foodLocX = ((r * TWIDTH));

         r = (int) (Math.random() * RAND_POS);
         foodLocY = ((r * THEIGHT));
    }
}

public void paint(Graphics g) {
    g.clearRect(0, 0, WIDTH, HEIGHT);
    g.setColor(Color.GREEN);
    for(int i = 0; i<WIDTH;i+=TWIDTH) {
        for(int ii = 0; ii<HEIGHT;ii+=THEIGHT) {
            g.fillRect(i, ii, TWIDTH, THEIGHT);
        }
    }

    if(foodLocX == body.get(0).getX() && foodLocY == body.get(0).getY()) {
        int x = body.get(body.size()-1).getX();
        int y = body.get(body.size()-1).getY();

        if(right) {
            body.add(new BodyPart(x+20,y,TWIDTH));
        }if(left) {
            body.add(new BodyPart(x-20,y,TWIDTH));
        }if(down) {
            body.add(new BodyPart(x,y+20,TWIDTH));
        }if(up) {
            body.add(new BodyPart(x,y-20,TWIDTH));
        }
        locateApple();
    }
    g.setColor(Color.RED);
    g.fillRect(foodLocX, foodLocY, TWIDTH, THEIGHT);
    g.setColor(Color.BLACK);
    for(int i = 0; i< body.size();i++) {
        body.get(i).draw(g);
    }
    repaint();
}

@Override
public void keyPressed(KeyEvent e) {
    if(e.getKeyCode() == KeyEvent.VK_UP && !down) {
        up = true;
        down = false;
        left = false;
        right = false;
        try {
            Thread.sleep(55,666);
        } catch (InterruptedException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
    }else if(e.getKeyCode() == KeyEvent.VK_DOWN && !up) {
        up = false;
        down = true;
        left = false;
        right = false;
        try {
            Thread.sleep(55,666);
        } catch (InterruptedException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
    }else if(e.getKeyCode() == KeyEvent.VK_RIGHT && !left) {
        up = false;
        down = false;
        left = false;
        right = true;
        try {
            Thread.sleep(55,666);
        } catch (InterruptedException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
    }else if(e.getKeyCode() == KeyEvent.VK_LEFT && !right) {
        up = false;
        down = false;
        left = true;
        right = false;
        try {
            Thread.sleep(100,666);
        } catch (InterruptedException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
    }

}
@Override
public void keyReleased(KeyEvent arg0){};
@Override
public void keyTyped(KeyEvent arg0){}

//public void addBodyPart() {
    //body.add(previousHead); // Part that I left off on
//}

public void moveSnake() {
    if(right) {
        for(int i = 0; i<body.size();i++) {
            body.get(i).setX(body.get(i).getX()+20);
        }
    }if(left) {
        for(int i = 0; i<body.size();i++) {
            body.get(i).setX(body.get(i).getX()-20);
        }
    }if(down) {
        for(int i = 0; i<body.size();i++) {
            body.get(i).setY(body.get(i).getY()+20);
        }
    }if(up) {
        for(int i = 0; i<body.size();i++) {
            body.get(i).setY(body.get(i).getY()-20);
        }
    }
}
@Override
public void run() {
    while(running) {

        if(body.get(0).getX()<0 || body.get(0).getX()>480 || body.get(0).getY()<0 || body.get(0).getY()>480){
            System.out.println("Game Over!\nYour snake was " + body.size() + " blocks long");
            endGame();
        }

        moveSnake();

        repaint();
        try {
            Thread.sleep(75,666);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

public void startGame() {
    t.start();
}

public void endGame() {
    t.stop();
}
}

Main.java(可运行程序)

package snake;

public class Main {

    public static void main(String[] args) {
        Board b = new Board();
        b.startGame();
    }

}

BodyPart.java

package snake;

import java.awt.Color;
import java.awt.Graphics;

public class BodyPart {

    private int x,y,tilesize;
    public BodyPart(int x, int y, int tilesize) {
        this.x = x;
        this.y = y;
        this.tilesize = tilesize;
    }

    public void draw(Graphics g) {
        g.setColor(Color.BLACK);
        g.fillRect(x,y,tilesize,tilesize);
    }

    public int getX() {
        return x;
    }

    public int getY() {
        return y;
    }

    public void setX(int x) {
        this.x = x;
    }

    public void setY(int y) {
        this.y = y;
    }
}

这让我很困扰，因为它将 body 部位添加到数组列表中，但是一旦我移动，这些部位就不会跟随 body 。我迷路了，不知道该怎么办。任何帮助将不胜感激。非常感谢大家。

-AbysssCoder

Answer 1

因为在 moveSnake() 方法中，您正在迭代 body 并将 body 的每个部分移动相同的量(您拿起整条蛇并移动它，而不是拥有它“滑行”)。

您不需要移动整个蛇 - 您需要使用箭头键来移动“头”或“父级”。然后，您需要将蛇的其余部分编码为“子级”，其中蛇的每个新部分将其新位置设置为其父级的当前位置。

例如，如果您的蛇只有 2 个单位长，则箭头键将确定第一个单位(仅“头”)的位置。然后对于每个 bodypart : yoursnake (psuedocode)，您可以将新位置设置为 bodyPart.getParentBodyPart.getLocation() 或类似逻辑的内容。

这很丑，因为我只是把它和你拥有的东西放在一起 - 你绝对可以清理它。但它会起作用:

public void moveSnake() {
    if(right) {
        // iterate from the tail forward so we don't overwrite positions that we need
        for(int i = body.size()-1; i>=0;i--) {
            if (i == 0) {
                body.get(i).setX(body.get(i).getX()+20);
            } else {
                // we dont know what direct we are moving, so we need x and y
                body.get(i).setX(body.get(i-1).getX());
                body.get(i).setY(body.get(i-1).getY());
            }

        }
    }if(left) {
        for(int i = body.size()-1; i>=0;i--) {
            if (i == 0) {
                body.get(i).setX(body.get(i).getX()-20);
            } else {
                body.get(i).setX(body.get(i-1).getX());
                body.get(i).setY(body.get(i-1).getY());
            }

        }
    }if(down) {
        for(int i = body.size()-1; i>=0;i--) {
            if (i == 0) {
                body.get(i).setY(body.get(i).getY()+20);
            } else {
                body.get(i).setY(body.get(i-1).getY());
                body.get(i).setX(body.get(i-1).getX());
            }

        }
    }if(up) {
        for(int i = body.size()-1; i>=0;i--) {
            if (i == 0) {
                body.get(i).setY(body.get(i).getY()-20);
            } else {
                body.get(i).setY(body.get(i-1).getY());
                body.get(i).setX(body.get(i-1).getX());
            }

        }
    }
}