distanceTo() 方法返回 0.0km。为什么？

Question

我想通过 distanceTo() 方法计算 android 中两个位置 (GeoPoint) 之间的距离，但是当我运行程序时，该方法返回 0.0 并且程序显示 0.0KM。为什么？有什么问题？

public class MyLocation extends MapActivity {
    GeoPoint mylocation;
    @Override
    public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
          setContentView(R.layout.location);
        text_location.setOnKeyListener(new OnKeyListener(){
  public boolean onKey(View view, int keyCode,KeyEvent event){
      if(keyCode==KeyEvent.KEYCODE_ENTER){
                // The map should shows a location that user writes in edittex.
    Geocoder geo=new Geocoder(getApplicationContext(),Locale.getDefault());
    List<Address> address;
    try {
      address = geo.getFromLocationName(text_location.getText().toString(),3);
      if(address.size()>0){
      searchLocation=new GeoPoint((int)(address.get(0).getLatitude()*1e6),(int)(address.get(0).getLongitude()*1e6));
       float distance=0;
       distance=Distance(searchLocation);
        OverlayItem overlayItem=new OverlayIte(searchLocation,textLocation,"Distance:"+distance+"km");
      itemizedOverlay.addOverlay(overlayItem);                  mapOverlays.add(itemizedOverlay);
                        //
}
} catch (IOException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
}   
        return true;
   }
   return false;
  }
 });
 }
   private void initMyLocation() {
    final MyLocationOverlay overlay = new MyLocationOverlay(this, map);
    overlay.enableMyLocation();
    overlay.enableCompass(); 
    //
    mylocation=overlay.getMyLocation();
    overlay.runOnFirstFix(new Runnable() {
        public void run() {
            controller.setZoom(13);
            controller.animateTo(overlay.getMyLocation());
        }
    });

}
    private float Distance(GeoPoint searchLoc){
    Location a=new Location("locA");
    Location b=new Location("locB");
    if(mylocation!=null){
        a.setLatitude(mylocation.getLatitudeE6()/1e6);
        a.setLongitude(mylocation.getLongitudeE6()/1e6);
        b.setLatitude(searchLoc.getLatitudeE6()/1e6);
        b.setLongitude(searchLoc.getLongitudeE6()/1e6);
    }
               if(a.getLatitude()!=0)
        Log.i("this", "is not zero");
    else
        Log.i("this", "is zero");

    float distance=a.distanceTo(b);
    return distance;
}   
 }

我编辑帖子并添加初始化 myLocation 变量的 initMyLocation() 方法，并将日志添加到 Distance() 方法以检查 a 或 b 的值。

谢谢。干杯

Answer 1

你可以这样试试

public double distance(float lata, float longa, float latb, float longb) {
    double d2r = Math.PI / 180;
    double dlong = (longa - longb) * d2r;
    double dlat = (lata - latb) * d2r;
    double a = Math.pow(Math.sin(dlat / 2.0), 2) + Math.cos(latb * d2r)
            * Math.cos(lata * d2r) * Math.pow(Math.sin(dlong / 2.0), 2);
    double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
    double d = 6367 * c;
    return d;

}