cannot obtain current geographic location in android

i have to make an android application in which i need to find the users current location and then obtain a bunch of lat and longs from a database. After this i need to find the distance between the users current location and the lat ,longs.... and for all those distances which are less than 200km i need to add them to a list.

PROBLEM: i am not able to find the current user location and i always obtain 0,0. I have tested the same on an emulator by passing the co-ordinates using DDMS. I have also tried the same on an actual device still i receive 0,0 as the lat, long. Also the distance being calculated is incorrect.

Here is my code:

    LocationManager lm;
LocationListener ll;
@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.nearactivity);
    mHandler= new Handler();
    lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    ll = new mylocationlistener();
    lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, ll);
    showProgress();
}

private void showProgress() {
    pd = new ProgressDialog(NearActivity.this);
    pd.setTitle("Nautic-Dates");
    pd.setMessage("Loading");
    pd.show();
    GetLocations gl = new GetLocations();
    gl.execute();
    try {
        setListAdapter(new CustomeAdapter(gl.get()));
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (ExecutionException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    pd.dismiss();
}

public class GetLocations extends AsyncTask<Void, Void, ArrayList<String>> {

    @Override
    protected ArrayList<String> doInBackground(Void... arg0) {
        HandleDatabase hb = new HandleDatabase();
        String locations[] = hb.getLocationsFromDatabase();
        ArrayList<String> nearlocations = new ArrayList<String>();
        CustomGeoCoder cg = new CustomGeoCoder();
        for (int i = 0; i < locations.length; i++) {
            String details[] = locations[i].split("--");
            if (details[0].trim().equals("")
                    || details[1].trim().equals("")||details[0].trim().equals("null")
                    || details[1].trim().equals("null")) {
                continue;
            } else {
                float distance = cg.checkLocation(details[0], details[1]);
                if (distance<RADIUS) {
                    nearlocations.add(locations[i]+"--"+distance);
                }
            }
        }
        return  nearlocations;
    }

}

public class CustomGeoCoder {


    public float checkLocation(String string, String string2) {
        Location locationA = new Location("pointA");

        Log.i("current loc", "lat " + lat + " lng " + lng);
        Log.i("checklocation loc", "lat " + string + " lng " + string2);
        locationA.setLatitude(lat);
        locationA.setLongitude(lng);

        Location locationB = new Location("pointB");

        try {
            locationB.setLatitude(Double.parseDouble(string));
        } catch (NumberFormatException e) {
            try {
                locationB.setLatitude(Float.parseFloat(string));
            } catch (NumberFormatException e1) {
                try {
                    locationB.setLatitude(Integer.parseInt(string));
                } catch (NumberFormatException e2) {
                    e2.printStackTrace();
                    return RADIUS+1;
                }

            }
        }
        try {
            locationB.setLongitude(Double.parseDouble(string2));
        } catch (NumberFormatException e) {
            try {
                locationB.setLongitude(Float.parseFloat(string2));
            } catch (NumberFormatException e1) {
                try {
                    locationB.setLongitude(Integer.parseInt(string2));
                } catch (NumberFormatException e2) {
                    e2.printStackTrace();
                    return RADIUS+1;
                }
            }
        }

        float distance = locationA.distanceTo(locationB);

//this code is returning wrong values.
        return distance/1000;
//          Log.i("distance", "" + distance);
//          if (distance / 1000 > RADIUS)
//              return false;
//          else
//              return true;
    }

}

private class mylocationlistener implements LocationListener {
    @Override
    public void onLocationChanged(Location location) {
        if (location != null) {
            Log.d("LOCATION CHANGED", location.getLatitude() + "");
            Log.d("LOCATION CHANGED", location.getLongitude() + "");
            lat = location.getLatitude();
            lng = location.getLongitude();
            Toast.makeText(NearActivity.this,"lng="+lng+" lat="+lat, Toast.LENGTH_SHORT);
            showProgress();
        }
    }

    @Override
    public void onProviderDisabled(String provider) {
    }

    @Override
    public void onProviderEnabled(String provider) {
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
    }
}

i am not able to understand what is going wrong?

thank you in advance for your he开发者_StackOverflow中文版lp.

I've loaded your code in Eclipse, and although I haven't got it to run, because I obviously don't have your HandleDatabase class code, nor your CustomAdapter. However, what struck me, is it appears you're reusing using lat and lon as object members for the Activity, or you've not defined them as variables within the methods they're used. I suggest breaking up your code into self contained units which people here could more easily debug for you.