bullet.java

用j2me编写的手机游戏开发的模块 它实现了子弹的移动以及冲突的检测灯功能

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());
		}
}