来源: 互联网  发布时间: 2014-02-18

计算两经纬度之间的位置
#define PI 3.1415926
double LantitudeLongitudeDist(double lon1,double lat1,
  double lon2,double lat2)
{
double er = 6378137; // 6378700.0f;
//ave. radius = 6371.315 (someone said more accurate is 6366.707)
//equatorial radius = 6378.388
//nautical mile = 1.15078
double radlat1 = PI*lat1/180.0f;
double radlat2 = PI*lat2/180.0f;
//now long.
double radlong1 = PI*lon1/180.0f;
double radlong2 = PI*lon2/180.0f;
if( radlat1 < 0 ) radlat1 = PI/2 + fabs(radlat1);// south
if( radlat1 > 0 ) radlat1 = PI/2 - fabs(radlat1);// north
if( radlong1 < 0 ) radlong1 = PI*2 - fabs(radlong1);//west
if( radlat2 < 0 ) radlat2 = PI/2 + fabs(radlat2);// south
if( radlat2 > 0 ) radlat2 = PI/2 - fabs(radlat2);// north
if( radlong2 < 0 ) radlong2 = PI*2 - fabs(radlong2);// west
//spherical coordinates x=r*cos(ag)sin(at), y=r*sin(ag)*sin(at), z=r*cos(at)
//zero ag is up so reverse lat
double x1 = er * cos(radlong1) * sin(radlat1);
double y1 = er * sin(radlong1) * sin(radlat1);
double z1 = er * cos(radlat1);
double x2 = er * cos(radlong2) * sin(radlat2);
double y2 = er * sin(radlong2) * sin(radlat2);
double z2 = er * cos(radlat2);
double d = sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2)+(z1-z2)*(z1-z2));
//side, side, side, law of cosines and arccos
double theta = acos((er*er+er*er-d*d)/(2*er*er));
double dist  = theta*er;
return dist;
}

    

    来源: 互联网  发布时间: 2014-02-18

Runnable 和 Thread

我们都知道创建线程有两个方法:  一是通过继承Thread类;二是向Thread类传递一个Runnable对象.

比如说一个售票站有四个窗口卖票,我们要设计四个线程

第一种方法:传递一个Runnable对象.

public class MyThread
{
 public static void main(String[] args)
 {
  TestThread tt = new TestThread();
  new Thread(tt).start();
  new Thread(tt).start();
  new Thread(tt).start();
  new Thread(tt).start(); 
}
}  
class TestThread implements Runnable
{
 public int ticket = 100;
 public void run()
 {
  while(ticket>0)
  {
   System.out.println(Thread.currentThread().getName()+"is saling ticket"+ticket--);
  }
 }
}

 

 二.通过继承Thread类

public class MyThread
{
 public static void main(String[] args)
 {
  TestThread tt1 = new TestThread().start();
  TestThread tt2= new TestThread().start();                  
TestThread tt3 = new TestThread().start();
TestThread tt4 = new TestThread().start();


}
}
class TestThread implements Runnable
{
 public int ticket = 100;
 public void run()
 {
  while(ticket>0)
  {
   System.out.println(Thread.currentThread().getName()+"is saling ticket"+ticket--);
  }
 }
}
 

 结论：

方法一中四个线程是合作卖100张,而方法二中是四个线程分别各卖100张,就是说四个线程都会卖同一张票四次。

也就是说Runnalbe 是多个对象同时跑一个run，Thread是各自跑各自的

 

    

    来源: 互联网  发布时间: 2014-02-18

Bitmap，byte流，drawable之相互转换

刚开始学习android，以前学习J2me的时候也碰到过类似的问题，现在看到有同学总结过了，地址为：http://www.iteye.com/topic/642128 
   这里全文摘抄，以备学习：） 
1、Drawable → Bitmap 
Java代码 
public static Bitmap drawableToBitmap(Drawable drawable) {  
          
        Bitmap bitmap = Bitmap  
                        .createBitmap(  
                                        drawable.getIntrinsicWidth(),  
                                        drawable.getIntrinsicHeight(),  
                                        drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888  
                                                        : Bitmap.Config.RGB_565);  
        Canvas canvas = new Canvas(bitmap);  
        //canvas.setBitmap(bitmap);  
        drawable.setBounds(0, 0, drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight());  
        drawable.draw(canvas);  
        return bitmap;  
}  

2、从资源中获取Bitmap 

Java代码 
Resources res=getResources();  
  
Bitmap bmp=BitmapFactory.decodeResource(res, R.drawable.pic);  

3、Bitmap → byte[] 

Java代码 
private byte[] Bitmap2Bytes(Bitmap bm){  
    ByteArrayOutputStream baos = new ByteArrayOutputStream();    
    bm.compress(Bitmap.CompressFormat.PNG, 100, baos);    
    return baos.toByteArray();  
   }  

4、 byte[] → Bitmap 
Java代码 
private Bitmap Bytes2Bimap(byte[] b){  
            if(b.length!=0){  
                return BitmapFactory.decodeByteArray(b, 0, b.length);  
            }  
            else {  
                return null;  
            }  
      }