some issue in detecting location application crashes

Question 1

location is never initialized. Your are setting location as the variable that will hold the return value of getUserLocation() and it is also its parameter; both are null.

Question 2

public class MainActivity extends MapActivity implements LocationListener {

private MapView mapView;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    // Getting reference to MapView
    mapView = (MapView) findViewById(R.id.map_view);

    // Setting Zoom Controls on MapView
    mapView.setBuiltInZoomControls(true);

    // Getting LocationManager object from System Service LOCATION_SERVICE
    LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);

    // Creating a criteria object to retrieve provider
    Criteria criteria = new Criteria();

    // Getting the name of the best provider
    String provider = locationManager.getBestProvider(criteria, true);

    // Getting Current Location
    Location location = locationManager.getLastKnownLocation(provider);

    if(location!=null){
        onLocationChanged(location);
    }

    locationManager.requestLocationUpdates(provider, 20000, 0, this);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}

@Override
protected boolean isRouteDisplayed() {
    // TODO Auto-generated method stub
    return false;
}

@Override
public void onLocationChanged(Location location) {
    TextView tvLocation = (TextView) findViewById(R.id.tv_location);

    // Getting latitude
    double latitude = location.getLatitude();

    // Getting longitude
    double longitude = location.getLongitude();

    // Setting latitude and longitude in the TextView tv_location
    tvLocation.setText("Latitude:" +  latitude  + ", Longitude:"+ longitude );

    // Creating an instance of GeoPoint corresponding to latitude and longitude
    GeoPoint point = new GeoPoint((int)(latitude * 1E6), (int)(longitude*1E6));

    // Getting MapController
    MapController mapController = mapView.getController();

    // Locating the Geographical point in the Map
    mapController.animateTo(point);

    // Applying a zoom
    mapController.setZoom(15);

    // Redraw the map
    mapView.invalidate();

    // Getting list of overlays available in the map
    List<Overlay> mapOverlays = mapView.getOverlays();

    // Creating a drawable object to represent the image of mark in the map
    Drawable drawable = this.getResources().getDrawable(R.drawable.cur_position);

    // Creating an instance of ItemizedOverlay to mark the current location in the map
    CurrentLocationOverlay currentLocationOverlay = new CurrentLocationOverlay(drawable);

    // Creating an item to represent a mark in the overlay
    OverlayItem currentLocation = new OverlayItem(point, "Current Location", "Latitude : " + latitude + ", Longitude:" + longitude);

    // Adding the mark to the overlay
    currentLocationOverlay.addOverlay(currentLocation);

    // Clear Existing overlays in the map
    mapOverlays.clear();

    // Adding new overlay to map overlay
    mapOverlays.add(currentLocationOverlay);

}

@Override
public void onProviderDisabled(String provider) {
    // TODO Auto-generated method stub
}

@Override
public void onProviderEnabled(String provider) {
    // TODO Auto-generated method stub
}

@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
    // TODO Auto-generated method stub
}
}

Download Here