I want to return a string array from Async class back to the activity that is calling this asynchronous class that is job is to do the reverse geocoding.
So, from my activity I call the constructor of the class like this:
Double[] lat_long = new Double[] { Double.parseDouble(map_lat), Double.parseDouble(map_long) };
            ReverseGeocodingTask reverseGeocoding = new ReverseGeocodingTask(getActivity().getApplicationContext());
            reverseGeocoding.execute(lat_long);
And this is the code of the class:
class ReverseGeocodingTask extends AsyncTask<Double, Void, List<String>> {
    public static List<String> LIST = new ArrayList<String>();
    Context mContext;
    public ReverseGeocodingTask(Context context) {
        super();
        mContext = context;
    }
    @Override
    protected List<String> doInBackground(Double... params) {
        Geocoder gc= new Geocoder(mContext, Locale.getDefault());
        List<Address> addrList = null;
        double latitude = params[0].doubleValue();
        double longitude = params[1].doubleValue();
        Log.d("LATLONG", latitude + ":" + longitude);
        try {
            addrList = gc.getFromLocation(latitude, longitude, 1);
            if (addrList.size() > 0) {
                //format location info
                Address address = addrList.get(0);
                LIST.add(address.getLocality());
                LIST.add(address.getSubAdminArea());
                LIST.add(address.getCountryName());
                Log.d("LIST", LIST.get(0));
            }
            else{
                Log.d("addrList SIZE", "=0");
                return null;
            }
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
        return LIST;
    }
    @Override
    protected void onPostExecute(List<String> result) {
        if (result != null) {
            Log.d("ON POST", result.get(0));
        }
    }
}
This is the logcat:
02-28 19:20:04.323  12275-14109/guide_me_for_all.guide_me_for_all D/LATLONG﹕ 34.681377999999995:33.039339
02-28 19:20:05.434  12275-14109/guide_me_for_all.guide_me_for_all D/addrList SIZE﹕ =0
I get correctly the latitude and longitude point as you can see from the Log.d(), BUT getFromLocation.size() is always 0.