java - java中如何让 Sprite 跳跃？

Question

我有用于左、右、上、下移动的 Sprite 的 KeyEvents。我只是在闲逛，正在考虑另一个我希望 Sprite 跳跃的项目。它不必完全现实，因为我才刚刚开始。我所拥有的是，当按下空格键时，它将导致 Sprite 跳跃，让我们说“dy = -3”。那么我就有了 keyReleased 的 KeyEvent，它会下降，“dy = -2”。这不起作用，因为 Sprite 继续下落......有人可以发光吗？

整个代码: 包碰撞；

    import java.awt.Image;
    import java.awt.Rectangle;
    import java.awt.event.KeyEvent;

    import java.util.ArrayList;

    import javax.swing.ImageIcon;

    public class Craft {

    private String craft = "pelican.png";

    private int dx;
    private int dy;
    private int x;
    private int y;
    private int width;
    private int height;
    private boolean visible;
    private Image image;
    private ArrayList missiles;


    public Craft() {
    ImageIcon ii = new ImageIcon(this.getClass().getResource(craft));
    image = ii.getImage();
    width = image.getWidth(null);
    height = image.getHeight(null);
    missiles = new ArrayList();
    visible = true;
    x = 100;
    y = 300;
    }


    public void move() {

    x += dx;
    y += dy;

    if (x < 1) {
        x = 1;
    }

    if (y < 1) {
        y = 1;
    }

    }

    public int getX() {
    return x;
    }

    public int getY() {
    return y;
    }

    public Image getImage() {
    return image;
    }

    public ArrayList getMissiles() {
    return missiles;
    }

    public void setVisible(boolean visible) {
    this.visible = visible;
    }

    public boolean isVisible() {
    return visible;
    }

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

    public void keyPressed(KeyEvent e) {

    int key = e.getKeyCode();

    if (key == KeyEvent.VK_SPACE) {

    }
    if (key == KeyEvent.VK_V){
        dx = 6;
    }

    if (key == KeyEvent.VK_LEFT) {
        dx = -1;
    }

    if (key == KeyEvent.VK_RIGHT) {
        dx = 2;
    }

    if (key == KeyEvent.VK_UP) {
        dy = -1;
    }

    if (key == KeyEvent.VK_DOWN) {
        dy = 1;
    }
    }

    public void fire() {
    missiles.add(new Missile(x + width, y + height/2));
    }

    public void keyReleased(KeyEvent e) {
    int key = e.getKeyCode();

    if (key == KeyEvent.VK_LEFT) {
        dx = 0;
    }
    if (key == KeyEvent.VK_SPACE) {

    }

    if (key == KeyEvent.VK_RIGHT) {
        dx = 0;
    }

    if (key == KeyEvent.VK_UP) {
        dy = 0;
    }

    if (key == KeyEvent.VK_DOWN) {
        dy = 0;
    }
    }
    }

您可能已经注意到，我对 Java 和游戏编程都很陌生。我想要的只是让 Sprite 上升，然后再下降。如果有帮助的话，它将始终保持静止。 Sprite 会一直跳跃，直到被迎面而来的障碍物击中。我知道还有其他 Action 的代码，但是一旦我开始下一个 Sprite ，这些代码就会被删除。

Answer 1

这是基本概念。您的实现将根据引擎的实现而变化。

基本思想是玩家有一个垂直增量，该增量会随着时间的推移而因重力而变化。这会影响 Sprite 的垂直速度。

这个实现还有一个重新绑定(bind)增量，它允许 Sprite 重新绑定(bind)而不是突然“停止”。重新绑定(bind)受到重新绑定(bind)降级的影响，这会减少每次重新绑定(bind)的重新绑定(bind)量。

这模拟了游戏角色，因此您需要按空格才能开始弹跳...

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import javax.swing.AbstractAction;
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 JumpingSprite {

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

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

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

    public static class TestPane extends JPanel {

        protected static final int SPRITE_HEIGHT = 10;
        protected static final int SPRITE_WIDTH = 10;
        private float vDelta; // The vertical detla...
        private float rbDelta; // Rebound delta...
        private float rbDegDelta; // The amount the rebound is degradation...
        private int yPos; // The vertical position...
        private float gDelta; // Gravity, how much the vDelta will be reduced by over time...
        private Timer engine;
        private boolean bounce = false;

        public TestPane() {

            yPos = getPreferredSize().height - SPRITE_HEIGHT;
            vDelta = 0;
            gDelta = 0.25f;
            // This is how much the re-bound will degrade on each cycle...
            rbDegDelta = 2.5f;

            InputMap im = getInputMap(WHEN_IN_FOCUSED_WINDOW);
            ActionMap am = getActionMap();
            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_SPACE, 0), "jump");
            am.put("jump", new AbstractAction() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    // Can only bound when we're actually on the ground...
                    // You might want to add fudge factor here so that the 
                    // sprite can be within a given number of pixels in order to
                    // jump again...
                    if (yPos + SPRITE_HEIGHT == getHeight()) {
                        vDelta = -8;
                        rbDelta = vDelta;
                        bounce = true;
                    }
                }
            });

            engine = new Timer(40, new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    int height = getHeight();
                    // No point if we've not been sized...
                    if (height > 0) {
                        // Are we bouncing...
                        if (bounce) {
                            // Add the vDelta to the yPos
                            // vDelta may be postive or negative, allowing
                            // for both up and down movement...
                            yPos += vDelta;
                            // Add the gravity to the vDelta, this will slow down
                            // the upward movement and speed up the downward movement...
                            // You may wish to place a max speed to this
                            vDelta += gDelta;
                            // If the sprite is not on the ground...
                            if (yPos + SPRITE_HEIGHT >= height) {
                                // Seat the sprite on the ground
                                yPos = height - SPRITE_HEIGHT;
                                // If the re-bound delta is 0 or more then we've stopped
                                // bouncing...
                                if (rbDelta >= 0) {
                                    // Stop bouncing...
                                    bounce = false;
                                } else {
                                    // Add the re-bound degregation delta to the re-bound delta
                                    rbDelta += rbDegDelta;
                                    // Set the vDelta...
                                    vDelta = rbDelta;
                                }
                            }
                        }
                    }
                    repaint();
                }
            });
            engine.start();
        }

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

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            int width = getWidth() - 1;
            int xPos = (width - SPRITE_WIDTH) / 2;
            g2d.drawOval(xPos, yPos, SPRITE_WIDTH, SPRITE_HEIGHT);
            g2d.dispose();
        }
    }
}