Android游戏开发---关于实体的绘制与跟踪技术

public class Enemy
{
private int x, y;
private Bitmap ePlayer;
private boolean flag = true;//标记是否有效. 被击中后变为无效的.
private int dx, dy;	//飞机的偏移量
private int pWidth, pHeight;
private GameView gameView;
private EnemyBullet enemyBullet;

//getter and setter
public boolean isFlag()
{
return flag;
}

public void setFlag(boolean flag)
{
this.flag = flag;
}

public Enemy(View view)
{
gameView = (GameView) view;
pWidth = view.getWidth();
pHeight = view.getHeight();

x = new Random().nextInt(pWidth);	//敌机出现的位置0-320(屏幕宽度)
y = new Random().nextInt(50) - 50;		//上移50像素, 有高有低的慢慢出来

dy = new Random().nextInt(10) + 1;//1-10, 至少得动吧

ePlayer = BitmapFactory.decodeResource(view.getResources(),
R.drawable.e6);
}

public void drawSelf(Canvas canvas)
{
if (flag)   //敌机管理里面已经检测了
canvas.drawBitmap(ePlayer, x, y, null);
}

public void enemyCheckCrash()
{
//遍历所有子弹
for (PlayerBullet playerBullet : PlayerBulletManager
.getAllPlayerBullet())
{
//如果敌机和玩家子弹都是有效的, 且发生碰撞
if (this.flag == true
&& playerBullet.isFlag() == true
&& CheckCrash
.ifCrash(
x,
y,
x + ePlayer.getWidth(),
y + ePlayer.getHeight(),
playerBullet.getX(),
playerBullet.getY(),
playerBullet.getX()
+ playerBullet.getBulletWidth(),
playerBullet.getY()
+ playerBullet.getBulletHeight()))
;
{
//打到后敌机消失, 玩家子弹消失
this.flag = false;
playerBullet.setFlag(false);

System.out
.println(x
+ " "
+ y
+ " "
+ (x + ePlayer.getWidth())
+ " "
+ (y + ePlayer.getHeight())
+ " "
+ playerBullet.getX()
+ " "
+ playerBullet.getY()
+ " "
+ (playerBullet.getX() + playerBullet
.getBulletWidth())
+ " "
+ (playerBullet.getY() + playerBullet
.getBulletHeight()));

}
}

}

/**
* 敌机移动是随机的. 包括出现也是随机的.
*/
public void move()
{
//将偏移量的设置放到这里, 让飞机每次生成时的偏移的变化的
int px = gameView.getPlayerManager().getPlayer().getX();
//跟踪功能, 即设置dx增量
if (px < x)		//玩家的位置在左边
dx = new Random().nextInt(3) - 3;//-3~-1
else if (px > x)//玩家的位置在右边
dx = new Random().nextInt(3) + 1; //1~3
else
//正对着
dx = 0;

//敌机慢慢移动
x += dx;
y += dy;
//敌机出屏幕后, 再重新回到上面去. 敌机中子弹了也要回到上面去
if (x < -1 * ePlayer.getWidth() || x > pWidth || y > pHeight)
//|| this.flag == false)
{
x = new Random().nextInt(pWidth);//敌机出现的位置0-320(屏幕宽度)
y = new Random().nextInt(50) - 50;		//上移50像素, 有高有低的慢慢出来
//this.flag = true; 		//飞机又重新有效
}
}

/**
* 敌机发射子弹
*/
public void fire()
{
enemyBullet = gameView.getEnemyBulletManager().getOneBullet();
//设置子弹的位置.
//x = 敌机当前x + 敌机宽度/2 - 子弹宽度/2
//y = 敌机当前y + 飞机高度   (子弹高度 这里就不计算了)
enemyBullet.setPosition(
x + ePlayer.getWidth() / 2 - enemyBullet.getEnemyBulletWidth()
/ 2, y + ePlayer.getHeight());
enemyBullet.setDy(dy + 3);//保证子弹比飞机快, 设置敌机子弹的移动增量
}
}