请高手帮帮忙，Java多线程与图形界面的有关问题

请高手帮帮忙，Java多线程与图形界面的问题
麻烦高手帮忙看一下，为什么按空格后炮弹不发射了，再按空格炮弹还不发射。（我想的是按空格炮弹发射，再按不发射；按一下发射一次也行）；小弟菜鸟，初学Java。

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.Random;
import java.lang.Math;
public class Pete extends JFrame
{
public enemytank enemy;
public enemytank1 enemy1;
public ammo ammo1;
public ammoo ammoo1;
public myammoo myammoo1;
public int i=0;
  PetePanel pete = new PetePanel();
public Pete() 
{
super("Tank Battle");
  setSize(512, 430);
setResizable(false);
enemy=new enemytank(pete);
enemy1=new enemytank1(pete);
ammo1=new ammo(pete);
ammoo1=new ammoo(pete);
myammoo1=new myammoo(pete);
  setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//添加窗口关闭
  JPanel pane = new JPanel();
  pane.setLayout(new GridLayout(1, 1, 15, 15));
  pane.add(pete);
  this.addKeyListener(new KeyAdapter(){//得到焦点，放frame容易获取焦点。
  @Override
  public void keyPressed(KeyEvent e)
{
  System.out.println("ppppp");
if (e.getKeyCode() == KeyEvent.VK_SPACE) //fire
{
i=i+1;
if(i%2==0)
  pete.live=1;
else pete.live=0;
System.out.println(pete.live);
  }
  }

  public void keyTyped(KeyEvent e)
{
  System.out.println("kkkkk");
  }

  public void keyReleased(KeyEvent e) 
{
  System.out.println("rrrrrr");
  }
  });
  setContentPane(pane);//建立联系与pane
enemy.start();
enemy1.start();
ammo1.start();
ammoo1.start();
myammoo1.start();
  this.setVisible(true);//窗口可见
  this.requestFocus();//具体办法可以手设焦点。如果焦点有问题，就优先想到它
}
public static void main(String[] arguments)
{
  Pete Penguin = new Pete();
  PetePanel a = new PetePanel();
  }
}

class PetePanel extends JPanel{
  Image petePics[] = new Image[4];
Image petePics1[] = new Image[4];
Image petePics2[] = new Image[4];
Image petePics3[] = new Image[4];
Image petePics4[] = new Image[4];
Image petePics5[] = new Image[4];
  Image back;
  int current = 0;
  int x = 100;
  int y = 100;
int current1 = 0;
  int x1 = 300;
  int y1 = 300;
int current2 = 0;
  int x2 = 400;
  int y2 = 50;
int current3 = 0;
  int x3 = -20;
  int y3 = -20;
int current4 = 0;
  int x4 = -20;
  int y4 = -20;
int current5 = 0;
  int x5 = -20;
  int y5 = -20;
int live=1;
PetePanel() 
{
  super();
  String peteSrc[] = { "right.jpg", "left.jpg", "up.jpg", "down.jpg" };
String peteSrc1[] = { "right.jpg", "left.jpg", "up.jpg", "down.jpg" };
String peteSrc2[] = { "right.jpg", "left.jpg", "up.jpg", "down.jpg" };
String peteSrc3[] = { "ar.jpg", "al.jpg", "au.jpg", "ad.jpg" };
String peteSrc4[] = { "ar.jpg", "al.jpg", "au.jpg", "ad.jpg" };
String peteSrc5[] = { "ar.jpg", "al.jpg", "au.jpg", "ad.jpg" };
  Toolkit kit = Toolkit.getDefaultToolkit();
  for (int i = 0; i < petePics.length; i++)