android: get location from GPS and mobile stations

I was working on a project, where I need to detect location of the device. User needs to tap a button in configuration page and location should be detected.
Detection only by GPS didn’t work on some Samsung devices. Pretty annoying problem, I should say.
So, I added some other methods to get coarse location in case GPS is not accessible for some reason:

private class RetrieveLocation extends AsyncTask
    {
    	private ProgressDialog progress = null;
    	private double lat ; 
    	private double lng ;
private LocationManager lm;
    private LocationListener locationListener;
    @Override
	protected Void doInBackground(Void... params) {
    			Looper.myLooper().prepare(); //This string makes magic. Without this string, there was an exception "Cant Create Handler Inside Thread That Has Not Called Looper Prepare in Android"
lm = (LocationManager) 
	    	            getSystemService(Context.LOCATION_SERVICE);    
	    	                locationListener = new MyLocationListener();
// Here starts fine location detection
    		        lm.requestLocationUpdates(
    		            LocationManager.GPS_PROVIDER, 
    		            30000, 
    		            30, 
    		            locationListener);
    		        
    				   Location locationM = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);
    			   
    				if (locationM != null) {
    					 lat = Double.parseDouble(numberFormat.format(locationM.getLatitude()));
    					 lng = Double.parseDouble(numberFormat.format(locationM.getLongitude()));
    					
    				}else{
// If fine location is not detected, we are trying to get network location

    					if (lm.isProviderEnabled(LocationManager.NETWORK_PROVIDER))
    					{
    						progress.setMessage("Mobile network location");
    					lm.requestLocationUpdates(
    				            LocationManager.NETWORK_PROVIDER, 
    				            30000, 
    				            30, 
    				            locationListener);
    				        
    						   locationM = lm.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
    						   if (locationM != null) {
    								 lat = Double.parseDouble(numberFormat.format(locationM.getLatitude()));
    								 lng = Double.parseDouble(numberFormat.format(locationM.getLongitude()));
    								
    							}
    					}else{
// if we failed again, we try we get coarse location from passive providers
    						progress.setMessage("Coarse location");
    						lm.requestLocationUpdates(
    					            LocationManager.PASSIVE_PROVIDER, 
    					            30000, 
    					            30, 
    					            locationListener);
    					        
    							   locationM = lm.getLastKnownLocation(LocationManager.PASSIVE_PROVIDER);
    							   if (locationM != null) {
    									 lat = Double.parseDouble(numberFormat.format(locationM.getLatitude()));
    									 lng = Double.parseDouble(numberFormat.format(locationM.getLongitude()));    									    								}
    					}
    				}              
    	  
	return null;
	}
    @Override
	protected void onCancelled() {
    		super.onCancelled();
    }

    @Override
	protected void onPreExecute() {
	progress = ProgressDialog.show(
			SettingsPage.this, null, "Detecting location...");

	super.onPreExecute();
	}
    @Override
	protected void onPostExecute(Void result) {
    	 // After the search is finished, we can do something with the results lat and lng.
		progress.dismiss();
		
		super.onPostExecute(result);
		}
    @Override
    protected void onProgressUpdate(Void... values) {
    	super.onProgressUpdate(values);
    	}
    }

Don’t forget to add to Manifest.xml