How to get last known location for Location manager in Android?

I am using simple location manager object to get lastKnownLocation() of device but getting null object in return can any one tell me why ?

Code :

public Location getLocation() {
    LocationManager locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);        
    if (locationManager != null) {          
        Location lastKnownLocationGPS = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
        if (lastKnownLocationGPS != null) {             
            return lastKnownLocationGPS;
        } else {                
            Location loc =  locationManager.getLastKnownLocation(LocationManager.PASSIVE_PROVIDER);
            System.out.println("1::"+loc);----getting null over here
            System.out.println("2::"+loc.getLatitude());
            return loc;
        }
    } else {            
        return null;
    }
}
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.location);
    getLocation();-----calling service

 }

permissions given :

 <uses-permission android:name="android.permission.INTERNET" />
 <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
 <uses-permission android:name="android.permission.READ_PHONE_STATE" />
 <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
 <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

so is anything missing to set up? I have checked my location service is on in device please give some links for working examples

Silly thing as answer to this ...I restarted my device ...and it worked...Please ensure that your service for location are enabled and working properly