www.pudn.com > Bullet.rar > Bullet.java

package chapter_11; 
 
import javax.microedition.lcdui.* ; 
import javax.microedition.lcdui.game.* ; 
import java.util.Random; 
 
public class Bullet extends Sprite{	//子弹类 
	boolean alive;	//是否出边界 
	public int w,h;	//子弹像素 
	double speed=2,mapx,mapy;	//子弹速度和屏幕边界 
	private double bx,by;	//子弹坐标 
	public double dx,dy;	//子弹速度的分向量 
	private double degree;	//子弹角度 
	public Random ran;	//子弹位置 
	public Bullet(Image img,int w,int h,int feix,int feiy,int mapx,int mapy){	//构造方法 
		super(img,w,h);	//父类构造方法 
		this.w=w;	//设置像素大小 
		this.h=h;	//设置像素大小 
		this.mapx=mapx; 
		this.mapy=mapy; 
		ran=new Random();	//产生随机数 
		this.reset_Bullet(feix,feiy);	 
		} 
	public int get_x(){ 
			return (int)bx; 
		} 
	public int get_y(){ 
			return (int)by; 
		} 
	 
	public void reset_Bullet(int aget_x,int aget_y){//初始化子弹 
	 	alive=true;	//子弹未出屏幕 
		if(ran.nextDouble()>=0.5)	//设置子弹出现方位和射出方向 
		{ 
			bx=ran.nextDouble() * (mapx - w); 
			if(ran.nextDouble() >= 0.5){ 
				by = 0; 
				degree = Float11.acos((aget_x - bx) /  
						Math.sqrt((bx - aget_x) * (bx-aget_x) + (by - aget_y) * (by - aget_y))) +  
						3.141592654 + 0.5235987757 / 3 * (ran.nextDouble() * 2 - 1.0); 
			}else{	 
				by = (double)mapy - h; 
				degree = Float11.acos((bx - aget_x) /  
						Math.sqrt((bx - aget_x) * (bx-aget_x) + (by - aget_y) * (by - aget_y))) +  
						6.283185308 + 0.5235987757 / 3 * (ran.nextDouble() * 2 - 1.0); 
			} 
		}else{ 
			by=ran.nextDouble() * (mapy - h); 
		    if(ran.nextDouble() >= 0.5){ 
		    	bx = 0; 
		    	degree = Float11.asin((aget_y - by) /  
		    			Math.sqrt((bx - aget_x) * (bx - aget_x) + (by-aget_y) * (by-aget_y))) +  
		    			3.141592654 + 0.5235987757 / 3 * (ran.nextDouble() * 2 - 1.0); 
		    }else{ 
		    	bx = (double)mapx - w; 
		    	degree = Float11.asin((by - aget_y) /  
		    			Math.sqrt((bx - aget_x) * (bx - aget_x) + (by - aget_y) * (by - aget_y))) +  
		    			6.283185308 + 0.5235987757 / 3 * (ran.nextDouble() * 2 - 1.0); 
		    	} 
		    } 
		setPosition(get_x(),get_y()); 
		dx = -Math.cos(degree) * speed;	//设置X方向上的速度 
		dy = -Math.sin(degree) * speed;	//设置Y方向上的速度s 
 	} 
	public boolean alived(){ 
		if(bx > mapx - w || bx < 0 || by > mapy - h || by < 0)  
			return false; 
		else  
			return true; 
		} 
	public void Bulletmove(){	//子弹移动 
		bx += dx; 
		by += dy; 
		setPosition(get_x(),get_y()); 
		} 
}