@KevinWorkman是正确的。你需要某种数据结构来容纳火球。在下面的示例中，我使用List的Fireball。
List<Fireball> fireBalls;
...
private class Fireball {
Image fireball;
int x = 150;
int y = 125;
public Fireball(Image image) {
fireball = image;
}
public void drawFireball(Graphics g) {
g.drawImage(fireball, x, y, 50, 50, null);
}
}
要绘制它们，我只是遍历它们。为了使它们向前移动，我只是增加了计时器中的x值，然后调用重绘
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
...
for (Fireball ball : fireBalls) {
ball.drawFireball(g);
}
}
这是完整的代码
import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;
import java.util.*;
import java.util.List;
import java.util.logging.*;
import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.Timer;
public class WannaBeStreetfighter extends JPanel {
private static final int D_W = 700;
private static final int D_H = 250;
private static final int X_INC = 10;
List<Fireball> fireBalls;
BufferedImage ryu;
BufferedImage fireball;
BufferedImage background;
public WannaBeStreetfighter() {
try {
ryu = ImageIO.read(new URL("http://www.sirlin.net/storage/street_fighter/ryu_hadoken_pose.png?__SQUARESPACE_CACHEVERSION=1226531909576"));
background = ImageIO.read(new URL("http://fightingstreet.com/folders/varIoUsinfofolder/ehondasbath/hondasfz3stage.gif"));
fireball = ImageIO.read(new URL("http://farm6.staticflickr.com/5480/12297371495_ec19ded155_o.png"));
} catch (IOException ex) {
Logger.getLogger(WannaBeStreetfighter.class.getName()).log(Level.SEVERE, null, ex);
}
fireBalls = new LinkedList<>();
Timer timer = new Timer(40, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
Iterator<Fireball> it = fireBalls.iterator();
while (it.hasNext()) {
Fireball ball = it.next();
if (ball.x > D_W) {
it.remove();
System.out.println(fireBalls.size());
} else {
ball.x += X_INC;
repaint();
}
}
}
});
timer.start();
InputMap inputMap = getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
inputMap.put(Keystroke.getKeystroke("SPACE"), "hadouken");
getActionMap().put("hadouken", new AbstractAction() {
@Override
public void actionPerformed(ActionEvent e) {
fireBalls.add(new Fireball(fireball));
}
});
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawImage(background, 0, 0, D_W, D_H, this);
g.drawImage(ryu, 50, 125, 150, 115, this);
for (Fireball ball : fireBalls) {
ball.drawFireball(g);
}
}
@Override
public Dimension getPreferredSize() {
return new Dimension(D_W, D_H);
}
private class Fireball {
Image fireball;
int x = 150;
int y = 125;
public Fireball(Image image) {
fireball = image;
}
public void drawFireball(Graphics g) {
g.drawImage(fireball, x, y, 75, 50, null);
}
}
public static void main(String[] args) {
SwingUtilities.invokelater(new Runnable() {
public void run() {
JFrame frame = new JFrame("Best Street fighter ever");
frame.setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new WannaBeStreetfighter());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
}
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