【问题标题】:SnakeGame how to make the tail follow the head?贪吃蛇游戏如何让尾巴跟随头部?
【发布时间】:2017-04-28 14:31:31
【问题描述】:

我正在制作一个蛇游戏,但我被困在让尾巴跟随头部的地方。我听说在头部和尾部使用添加和删除可以实现这一点,但我不知道从哪里开始。

到目前为止,这是我的代码:

Screen.java

public class Screen extends JPanel implements ActionListener, KeyListener {
    public static final JLabel statusbar = new JLabel("Default");
    public static final int WIDTH = 800, HEIGHT = 800;
    Timer t = new Timer(100, this);
    int x = 400;
    int y = 400;
    int size = 5; //increase size if eat 
    private boolean right = false, left = false, up = false, down = false;

    int head = 0;

    private LinkedList<BodyPart> snake = new LinkedList<BodyPart>();
    private BodyPart b;

    public Screen(){

        initSnake();

        t.start();
        addKeyListener(this);
        setFocusable(true);
        setFocusTraversalKeysEnabled(false);
    }

    public void update(){

    }

    public void direction(){
        if(right) x+=10;
        if(left) x-=10;
        if(up) y-=10;
        if(down) y+=10;
    }

    public void trackOutBound(){
        if(x < 0 || x > 800 || y < 0 || y > 800) {
            x = 400;
            y = 400;
        }
    }

    public void initSnake(){
        if(snake.size() == 0){
            b = new BodyPart(x, y);
            for(int i = 0; i < size; i++) {
                snake.add(b);
            }
            System.out.println(snake);
        }
    }

    public static void main(String[] args) {

    }

    @Override
    public void paintComponent(Graphics g){
        super.paintComponent(g);
        g.setColor(new Color(10, 50, 0));
        g.fillRect(0, 0, WIDTH, HEIGHT);

        g.setColor(Color.BLACK);
        for(int i = 0; i < WIDTH / 10; i++) {
            g.drawLine(i * 10, 0, i * 10, HEIGHT);
        }

        for(int i = 0; i < HEIGHT / 10; i++) {
            g.drawLine(0, i * 10, WIDTH, i * 10);
        }

        int tempx = 0, tempy = 0;
        int temp = 0;
        for(int i = 0; i < size; i++){
            if(i == head) {
                snake.get(i).x = x;
                snake.get(i).y = y;
                snake.get(i).draw(g);
                g.setColor(Color.blue);
                g.fillRect(x, y, 10, 10);
                g.setColor(Color.white);
                g.drawRect(x, y, 10, 10);
            } else if(i > 0 && up) {
                snake.get(i).x = x;
                snake.get(i).y = y + temp;
                snake.get(i).draw(g);
            } else if(i > 0 && down) {
                snake.get(i).x = x;
                snake.get(i).y = y - temp;
                snake.get(i).draw(g);
            } else if(i > 0 && left) {
                snake.get(i).x = x + temp;
                snake.get(i).y = y;
                snake.get(i).draw(g);
            } else if(i > 0 && right) {
                snake.get(i).x = x - temp;
                snake.get(i).y = y;
                snake.get(i).draw(g);
            }
            temp += 10;
        }

        /*
        if(snake.size() == 5){
            snake.add(b);
            size += 1;
        }
                */

    }

    @Override
    public void actionPerformed(ActionEvent e) {
        direction();
        trackOutBound();
        repaint();        
       // System.out.println(snake);
        statusbar.setText("(" + x + " , " + y + ")");
    }

    @Override
    public void keyTyped(KeyEvent e) {}

    @Override
    public void keyPressed(KeyEvent e) {
        int key = e.getKeyCode();
        if(key == KeyEvent.VK_RIGHT && !left) { 
            up = false;
            down = false;
            right = true;
        }
        if(key == KeyEvent.VK_LEFT && !right) { 
                up = false;
                down = false;
                left = true;
        }
        if(key == KeyEvent.VK_UP && !down) {
                left = false;
                right = false;
                up = true;
        }
        if(key == KeyEvent.VK_DOWN && !up) {
                left = false;
                right = false;
                down = true;
        } 
    }

    @Override
    public void keyReleased(KeyEvent e) {}
}

BodyPart.java

public class BodyPart {

    int x;
    int y;

    public BodyPart(int x, int y) {
        this.x = x;
        this.y = y;
    }
    public void draw(Graphics g) {
        this.x = x;
        this.y = y;
    g.setColor(Color.red);
        g.fillRect(x, y, 10, 10);
        g.setColor(Color.white);
        g.drawRect(x, y, 10, 10);
    }
}

Frame.java

public class Frame extends JPanel {
    private static JLabel statusbar = new JLabel("Default");

    public void statusbar(){
        statusbar = Screen.statusbar;
    }

    public static void main(String[] args) {
        JFrame f = new JFrame();
        Screen s = new Screen();
        f.add(s);

        f.add(statusbar, BorderLayout.SOUTH);
        f.setSize(800, 800);
        f.setVisible(true);
        f.setLocationRelativeTo(null);
        f.setResizable(false);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

现在这段代码只会让尾巴翻转到水平或垂直,是否可以使用这段代码让尾巴跟随头部?或者我需要更改我的代码?

谢谢

【问题讨论】:

  • 你需要知道蛇的每一部分都在哪里。当你画蛇时,你在每个点上画一些东西

标签: java swing


【解决方案1】:

基本思想是,您需要某种List,其中包含蛇的所有点。从概念上讲,List 将包含虚拟坐标,即1x1 将表示虚拟空间中的坐标,它表示虚拟板上的一个位置(具有一定的宽度和高度)。

然后您可以将其转换到屏幕上,这样就可以让蛇的每个部分都比单个像素大。所以,如果每个部分都是5x5 像素,那么屏幕上的1x1 实际上就是5x5

每次蛇移动时,您都会在头部添加一个新值,并从尾部删除最后一个值(假设它没有增长)。当您需要绘制蛇时,您只需遍历 List,绘制蛇的每个点。

下面是一个简单的例子,它使用了LinkedList,它将一个新的Point推到List上,形成一个新的头部,并在每个循环中删除最后一个元素(尾部)。

这基本上归结为...

snakeBody.removeLast();
snakeBody.push(new Point(xPos, yPos));

作为一个可运行的概念

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.util.LinkedList;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Snake {

    public static void main(String[] args) {
        new Snake();
    }

    public Snake() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public static class TestPane extends JPanel {

        public enum Direction {

            UP, DOWN, LEFT, RIGHT
        }

        private int xPos, yPos;

        private Direction direction = Direction.UP;

        private LinkedList<Point> snakeBody = new LinkedList<>();

        public TestPane() {
            xPos = 100;
            yPos = 100;

            for (int index = 0; index < 50; index++) {
                snakeBody.add(new Point(xPos, yPos));
            }

            bindKeyStrokeTo("up.pressed", KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0, false), new MoveAction(Direction.UP));
            bindKeyStrokeTo("down.pressed", KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0, false), new MoveAction(Direction.DOWN));

            bindKeyStrokeTo("left.pressed", KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0, false), new MoveAction(Direction.LEFT));
            bindKeyStrokeTo("right.pressed", KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0, false), new MoveAction(Direction.RIGHT));

            Timer timer = new Timer(40, new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    switch (direction) {
                        case UP:
                            yPos--;
                            break;
                        case DOWN:
                            yPos++;
                            break;
                        case LEFT:
                            xPos--;
                            break;
                        case RIGHT:
                            xPos++;
                            break;
                    }
                    if (yPos < 0) {
                        yPos--;
                    } else if (yPos > getHeight() - 1) {
                        yPos = getHeight() - 1;
                    }
                    if (xPos < 0) {
                        xPos--;
                    } else if (xPos > getWidth() - 1) {
                        xPos = getWidth() - 1;
                    }

                    snakeBody.removeLast();
                    snakeBody.push(new Point(xPos, yPos));
                    repaint();
                }
            });
            timer.start();
        }

        public void bindKeyStrokeTo(String name, KeyStroke keyStroke, Action action) {
            InputMap im = getInputMap(WHEN_IN_FOCUSED_WINDOW);
            ActionMap am = getActionMap();

            im.put(keyStroke, name);
            am.put(name, action);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setColor(Color.RED);
            for (Point p : snakeBody) {
                g2d.drawLine(p.x, p.y, p.x, p.y);
            }
            g2d.dispose();
        }

        public class MoveAction extends AbstractAction {

            private Direction moveIn;

            public MoveAction(Direction direction) {
                this.moveIn = direction;
            }

            @Override
            public void actionPerformed(ActionEvent e) {
                direction = this.moveIn;
            }

        }

    }

}

现在,它没有碰撞检测或其他功能,但你可以移动蛇,它会跟随自己

【讨论】:

    【解决方案2】:

    对于蛇式移动,您可以从尾部到头部,将每个BodyPart 位置移动到其前面的BodyPart 位置。对于头部,前面没有部分,因此您必须编写决定代码是简单地移动与前面部分相同的方向还是基于输入的新方向。然后更新屏幕。

    【讨论】:

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