MainActivity.java

import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.support.v4.widget.SwipeRefreshLayout;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ProgressBar;
import android.widget.Toast;

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

import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;

public class MainActivity extends AppCompatActivity {
    private static final String API_KEY = "PUT YOUR KEY HERE"; //put here your own api key
    private static final String LANGUAGE = "en-US";
    private static final String PAGE = "1";

    private List<MoviesResult> moviesResults = new ArrayList<>();
    private RestAdapter restAdapter;
    private Toolbar toolbar;

    private RecyclerView recyclerView;
    private MoviesAdapter moviesAdapter;
    private ProgressBar progressBar;
    private SwipeRefreshLayout swipeRefreshLayout;

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

        moviesAdapter = new MoviesAdapter(getApplicationContext(), moviesResults);
        progressBar = (ProgressBar) findViewById(R.id.progressBar);
        progressBar.setVisibility(View.VISIBLE);
        recyclerView = (RecyclerView) findViewById(R.id.rv_movies);
        recyclerView.setLayoutManager(new GridLayoutManager(this, 2));
        recyclerView.setAdapter(moviesAdapter);

        swipeRefreshLayout = (SwipeRefreshLayout) findViewById(R.id.swipe_refresh);
        swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
            @Override
            public void onRefresh() {
                moviesResults.clear();
                fetchData();
                moviesAdapter.notifyDataSetChanged();
            }
        });
    }

    @Override
    protected void onResume() {
        super.onResume();
        restAdapter = new RestAdapter();
        fetchData();
    }

    private void fetchData() {

        showMoviesDataView();
        // get shared preference value
        SharedPreferences sharedPrefs = PreferenceManager.getDefaultSharedPreferences(this);
        String orderBy = sharedPrefs.getString(
                getString(R.string.settings_order_by_key),
                getString(R.string.settings_order_by_default));
        if (orderBy.equals(getString(R.string.settings_order_by_most_popular))) {
            restAdapter.getEndpoint().callPopular(API_KEY, LANGUAGE, PAGE).enqueue(new Callback<Movies>() {
                @Override
                public void onResponse(Call<Movies> call, Response<Movies> response) {
                    progressBar.setVisibility(View.GONE);
                    swipeRefreshLayout.setRefreshing(false);
                    if (response.isSuccessful()) {
                        moviesResults.clear();
                        moviesResults.addAll(response.body().getResults());
                        moviesAdapter.notifyDataSetChanged();
                    }
                }

                @Override
                public void onFailure(Call<Movies> call, Throwable t) {
                    progressBar.setVisibility(View.GONE);
                    swipeRefreshLayout.setRefreshing(false);
                    Toast.makeText(MainActivity.this, "Load data error!", Toast.LENGTH_SHORT).show();
                    Log.e("MainActivity", "LOAD ERROR : " + t.getMessage());
                }
            });
        } else if (orderBy.equals(getString(R.string.settings_order_by_top_rated))) {
            restAdapter.getEndpoint().callTopRated(API_KEY, LANGUAGE, PAGE).enqueue(new Callback<Movies>() {
                @Override
                public void onResponse(Call<Movies> call, Response<Movies> response) {
                    progressBar.setVisibility(View.GONE);
                    swipeRefreshLayout.setRefreshing(false);
                    if (response.isSuccessful()) {
                        moviesResults.clear();
                        moviesResults.addAll(response.body().getResults());
                        moviesAdapter.notifyDataSetChanged();
                    }
                }

                @Override
                public void onFailure(Call<Movies> call, Throwable t) {
                    progressBar.setVisibility(View.GONE);
                    swipeRefreshLayout.setRefreshing(false);
                    Toast.makeText(MainActivity.this, "Load data error!", Toast.LENGTH_SHORT).show();
                    Log.e("MainActivity", "LOAD ERROR : " + t.getMessage());
                }
            });
        }
    }

    private void showMoviesDataView() {
        // movies are visible, error message is hidden
        recyclerView.setVisibility(View.VISIBLE);
    }

    private boolean isOnline() {
        ConnectivityManager cm =
                (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        try {
            NetworkInfo netInfo = cm != null ? cm.getActiveNetworkInfo() : null;
            return netInfo != null && netInfo.isConnectedOrConnecting();
        } catch (NullPointerException e) {
            e.printStackTrace();
        }
        return false;
    }

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

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if (item.getItemId() == R.id.settings) {
            // go to settings
            Intent intent = new Intent(MainActivity.this, SettingsActivity.class);
            startActivity(intent);
            return true;
        } else if (item.getItemId() == R.id.refresh) {
            fetchData();
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

}