Fragment that uses an AsyncTask to bring result by using a listener

MainActivityFrag.java

import android.content.Context;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.GridView;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.List;


public class MainActivityFrag extends Fragment implements FetchMovieListTask.OnLoadMoviesListener {

    private MovieAdapter adapter = null;

    public MainActivityFrag() {
    }

    @Override
    public void onStart() {
        super.onStart();
        updateMovieList();
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_main_activity, container, false);

        adapter = new MovieAdapter(getActivity(), new ArrayList<Info>());
        GridView gridView = view.findViewById(R.id.grid_view);
        gridView.setAdapter(adapter);

        gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Info item = adapter.getItem(position);
                Intent intent = new Intent(getContext(), DetailActivity.class);
                intent.putExtra(Info.class.getName(), item);
                startActivity(intent);
            }
        });

        return view;
    }

    private void updateMovieList() {
        String sortKey = getString(R.string.pref_sort_key);
        String sortVal = getString(R.string.pref_sort_label);
        String sort = PreferenceManager.getDefaultSharedPreferences(getContext()).getString(sortKey, sortVal);

        if (isOnline()) {
            FetchMovieListTask fetchMovieListTask = new FetchMovieListTask(this);
            fetchMovieListTask.execute(sort);
        } else {
            Toast.makeText(getContext(), "There is no internet connection.", Toast.LENGTH_LONG).show();
        }
    }

    @Override
    public void onSuccess(List<Info> result) {
        if (result != null) {
            adapter.clear();
            adapter.addAll(result);
        }
    }

    private boolean isOnline() {
        ConnectivityManager cm =
                (ConnectivityManager) getContext().getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo netInfo = cm.getActiveNetworkInfo();
        return netInfo != null && netInfo.isConnectedOrConnecting();
    }
}