抱歉，我不知道标题的字法。但是我正在做一个Java游戏，在屏幕的底部有一个桨，可以左右移动它，以避免掉落小行星。我正在使用桨，但是我不知道如何制作一颗下降的小行星。小行星现在将只是一个矩形。我还希望能够调整速度以及有多少小行星落下。这是我的代码：
public class Main extends Applet implements KeyListener, MouseListener {
private Rectangle rect;
private Rectangle asteroidrect;
private ArrayList<Integer> keysDown;
private Image dbImage;
private Graphics dbg;
Random randomGenerator = new Random();
int speed = 8;
int level = 1; // change to 0 once start menu works
int xpos, ypos;
int blockx = 0;
int blocky = 0;
int width = 1024;
int height = 768;
String version = "0.0.1";
public static final int START_X_POS = 160;
public static final int START_Y_POS = 160;
public static final int START_WIDTH = 256;
public static final int START_HEIGHT = 64;
boolean startClicked;
boolean asteroid = false;
public void init() {
setSize(width, height);
addKeyListener(this);
addMouseListener(this);
setBackground(Color.black);
Frame c = (Frame)this.getParent().getParent();
c.setTitle("Asteroid Attack - Version " + version);
keysDown = new ArrayList<Integer>();
rect = new Rectangle(460, 700, 64, 12);
asteroidrect = new Rectangle(0, 0, 48, 48);
addAsteroid();
}
public void update(Graphics g) {
dbImage = createImage(this.getSize().width, this.getSize().height);
dbg = dbImage.getGraphics ();
if (dbImage == null) {}
dbg.setColor(getBackground ());
dbg.fillRect(0, 0, this.getSize().width, this.getSize().height);
dbg.setColor(getForeground());
paint(dbg);
g.drawImage(dbImage, 0, 0, this);
}
public void paint(Graphics g) {
Graphics2D g2 = (Graphics2D)g;
if (level != 0) {
g2.setPaint(Color.gray);
g2.fill(rect);
//if (asteroid == true) {
g2.setPaint(Color.red);
g2.fill(asteroidrect);
//}
}
}
@Override
public void keyPressed(KeyEvent e) {
if (!keysDown.contains(e.getKeyCode()))
keysDown.add(new Integer(e.getKeyCode()));
moveChar();
}
@Override
public void keyReleased(KeyEvent e) {
keysDown.remove(new Integer(e.getKeyCode()));
}
public void moveChar() {
if (level != 0) {
int x = rect.x;
int y = rect.y;
if (keysDown.contains(KeyEvent.VK_LEFT)) {
x -= speed;
}
if (keysDown.contains(KeyEvent.VK_RIGHT)) {
x += speed;
}
rect.setLocation(x, y);
repaint();
}
}
public void addAsteroid() {
asteroid = true;
}
@Override
public void keyTyped(KeyEvent e) {}
@Override
public void mouseClicked(MouseEvent me) {
if (level == 0) {
xpos = me.getX();
ypos = me.getY();
if (xpos >= START_X_POS && ypos >= START_Y_POS && xpos <= START_X_POS + START_WIDTH && ypos <= START_X_POS + START_HEIGHT ) {
level = 1;
}
}
}
@Override
public void mouseEntered(MouseEvent me) {}
@Override
public void mouseExited(MouseEvent me) {}
@Override
public void mouseReleased(MouseEvent me) {}
@Override
public void mousePressed(MouseEvent me) {}
}
如您所见，我已经添加了一个小行星对象和一个矩形。
最佳答案
看看这个例子。我使用了三个具有不同x和y点的小行星（矩形）。我用不同的偏移量绘制它们。我使用了一个Sing定时器来设置重画的延迟。每隔毫秒，y位置将更改并重新绘制。我还添加了向上和向下的按键绑定，以减慢或加快延迟。如果您有任何问题，请告诉我。
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
import javax.swing.SwingUtilities;
import javax.swing.Timer;
public class Asteroids extends JPanel {
int astr1X = 50;
int astr1Y = 30;
int astr2X = 150; // x and y for 3 different asteriods
int astr2Y = 60;
int astr3X = 250;
int astr3Y = 45;
private final static int OFFSET = 5;
private final static int WIDTH = 20;
private final static int HEIGHT = 20;
private Timer timer = null;
public Asteroids() {
timer = new Timer(300, new ActionListener() { // timer with 150 millisecond delay
public void actionPerformed(ActionEvent e) {
astr1Y += OFFSET; // add 5 t the y poistion
astr2Y += OFFSET;
astr3Y += OFFSET;
repaint();
}
});
timer.start();
Action downAction = new AbstractAction() { // slows down the timer
public void actionPerformed(ActionEvent e) {
int delay = timer.getDelay();
if (delay < 1000) {
delay += 100;
timer.setDelay(delay);
}
}
};
Action upAction = new AbstractAction() { // speeds up the timer
public void actionPerformed(ActionEvent e) {
int delay = timer.getDelay();
if (delay > 100) {
delay -= 100;
timer.setDelay(delay);
}
}
};
getInputMap().put(KeyStroke.getKeyStroke("UP"), "upAction"); // up key binding
getActionMap().put("upAction", upAction);
getInputMap().put(KeyStroke.getKeyStroke("DOWN"), "downAction"); // down key binding
getActionMap().put("downAction", downAction);
}
private static void createAndShowGui() {
JFrame frame = new JFrame();
frame.add(new Asteroids());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setVisible(true);
}
public Dimension getPreferredSize() {
return new Dimension(350, 600);
}
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (astr1Y > 590) // if y is size of screen
astr1Y = 10; // make it 0. This brings
if (astr2Y > 590) // asteroid back to top
astr2Y = 10;
if (astr3Y > 590)
astr3Y = 10;
g.fillRect(astr1X, astr1Y, WIDTH, HEIGHT);
g.fillRect(astr2X, astr2Y, WIDTH, HEIGHT);
g.fillRect(astr3X, astr3Y, WIDTH, HEIGHT);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}