我对Java还是陌生的，我一直试图在Java的本机图形中复制SpaceInvaders。我已经完成了基本的机制，但是当玩家或外星人发射子弹时，游戏速度会大大降低。我试图找出是什么原因导致游戏变慢，但无法。
'''
public class Board extends JPanel implements KeyListener,ActionListener{
Ship ship;
Alien[] row1 = new Alien[10];
Alien[] row2 = new Alien[10];
Alien[] row3 = new Alien[10];
private Timer timer;
int DELAY = 16;
boolean reachedend = false;
Bullet bullet;
int lives;
public Board() {
setBackground(Color.BLACK);
addKeyListener(this);
lives = 3;
ship = new Ship();
fillAliens();
timer = new Timer(DELAY, this);
timer.start();
}
void fillAliens() {
for(int x=1;x<11;x++) {
row1[x-1] = new Alien(x*30+40,30);
row2[x-1] = new Alien(x*30+40,70);
row3[x-1] = new Alien(x*30+40,110);
}
}
void shoot() {
if(bullet==null) {
bullet = new Bullet(ship.x + ship.width/2,ship.y - ship.height/2,-1);
}
}
void drawAliens(Graphics2D g) {
g.setColor(Color.red);
for(int x=1;x<11;x++) {
if(row1[x-1].alive == true) {
g.fillRect(row1[x-1].x_loc, row1[x-1].y_loc, row1[x-1].width, row1[x-1].width);
}
if(row2[x-1].alive == true) {
g.fillRect(row2[x-1].x_loc, row2[x-1].y_loc, row2[x-1].width, row2[x-1].width);
}
if(row3[x-1].alive == true) {
g.fillRect(row3[x-1].x_loc, row3[x-1].y_loc, row3[x-1].width, row2[x-1].width);
}
}
}
public void addNotify() {
super.addNotify();
requestFocus();
}
void drawShip(Graphics2D g) {
g.fillRect(ship.x, ship.y, ship.width, ship.height);
}
@Override
public void keyPressed(KeyEvent e) {
int key = e.getKeyCode();
if(lives>0) {
if (key == KeyEvent.VK_SPACE) {
shoot();
}
if (key == KeyEvent.VK_LEFT) {
if(ship.x>=5) {
ship.x -= 5;
}
}
if (key == KeyEvent.VK_RIGHT) {
if(ship.x+ship.width<434) {
ship.x += 5;
}
}
}
repaint();
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
drawShip(g2);
drawAliens(g2);
drawBullet(g2);
drawAlienBullet(g2);
drawLives(g2);
}
private void drawLives(Graphics2D g2) {
g2.setColor(Color.white);
g2.drawString("Lives:", 10, 300);
for(int x=1; x<=lives;x++) {
g2.fillRect(15*x+30, 290, 10, 10);
}
}
private void drawBullet(Graphics2D g2) {
g2.setColor(Color.GREEN);
if(bullet!=null) {
g2.fillRect(bullet.x_loc, bullet.y_loc, bullet.width, bullet.height);
}
}
private void drawAlienBullet(Graphics2D g2) {
g2.setColor(Color.BLUE);
for(int x=0;x<10;x++) {
if(row3[x].bullet != null) {
g2.fillRect(row3[x].bullet.x_loc, row3[x].bullet.y_loc, row3[x].bullet.width, row3[x].bullet.height);
}
if(row2[x].bullet != null) {
g2.fillRect(row2[x].bullet.x_loc, row2[x].bullet.y_loc, row2[x].bullet.width, row2[x].bullet.height);
}
if(row1[x].bullet != null ) {
g2.fillRect(row1[x].bullet.x_loc, row1[x].bullet.y_loc, row1[x].bullet.width, row1[x].bullet.height);
}
}
}
private void bulletHitPlayer() {
for(int x=0;x<10;x++) {
if(row3[x].bullet != null) {
if(row3[x].bullet.y_loc >= 350) {
row3[x].bullet = null;
break;
}
}
if(row2[x].bullet != null) {
if(row2[x].bullet.y_loc >= 350) {
row2[x].bullet = null;
break;
}
}
if(row1[x].bullet != null) {
if(row1[x].bullet.y_loc >= 350) {
row1[x].bullet = null;
break;
}
}
if(row3[x].bullet != null && row3[x].bullet.y_loc + 10 >= ship.y && row3[x].bullet.y_loc <= ship.y + ship.height && row3[x].bullet.x_loc >= ship.x && row3[x].bullet.x_loc <= ship.x+ship.width) {
row3[x].bullet = null;
lives--;
break;
}
if(row2[x].bullet != null && row2[x].bullet.y_loc + 10 >= ship.y && row2[x].bullet.y_loc <= ship.y + ship.height && row2[x].bullet.x_loc >= ship.x && row2[x].bullet.x_loc <= ship.x+ship.width) {
row2[x].bullet = null;
lives--;
break;
}
if(row1[x].bullet != null && row1[x].bullet.y_loc + 10 >= ship.y && row1[x].bullet.y_loc <= ship.y + ship.height && row1[x].bullet.x_loc >= ship.x && row1[x].bullet.x_loc <= ship.x+ship.width) {
row1[x].bullet = null;
lives--;
break;
}
}
}
private void bulletHit() {
if(bullet!=null) {
for(int x=0;x<10;x++) {
if(row3[x].alive == true && bullet.y_loc >= row3[x].y_loc && bullet.y_loc <= row3[x].y_loc+row3[x].width && bullet.x_loc >= row3[x].x_loc && bullet.x_loc <= row3[x].x_loc+row3[x].width) {
row3[x].alive = false;
bullet=null;
break;
}
if(row2[x].alive == true && bullet.y_loc >= row2[x].y_loc && bullet.y_loc <= row2[x].y_loc+row2[x].width && bullet.x_loc >= row2[x].x_loc && bullet.x_loc <= row2[x].x_loc+row2[x].width) {
row2[x].alive = false;
bullet=null;
break;
}
if(row1[x].alive == true && bullet.y_loc >= row1[x].y_loc && bullet.y_loc <= row1[x].y_loc+row1[x].width && bullet.x_loc >= row1[x].x_loc && bullet.x_loc <= row1[x].x_loc+row1[x].width) {
row1[x].alive = false;
bullet=null;
break;
}
}
}
if(bullet!=null) {
if(bullet.y_loc<0) {
bullet=null;
}
}
}
@Override
public void keyTyped(KeyEvent e) {}
@Override
public void keyReleased(KeyEvent e) {}
@Override
public void actionPerformed(ActionEvent e) {
bulletHitPlayer();
bulletHit();
repaint();
}
}
'''
您的Timer仅绘制场景一次（请参阅API和[教程]¢https://docs.oracle.com/javase/tutorial/uiswing/misc/timer.html））-现在，您仅在按下键时重新绘制，这看起来很丑！” >
[创建Timer时，请允许它
timer.setRepeats(true);Timer：public void actionPerformed(ActionEvent e) {
bulletHitPlayer();
bulletHit();
repaint();
timer.restart(); //manually restart the timer
}