public class MainActivity extends AppCompatActivity
    implements NavigationView.OnNavigationItemSelectedListener {
android.support.v4.app.FragmentManager manager;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if (savedInstanceState != null) {
        String title_action_bar=savedInstanceState.getString("headerTitle");
        manager = getSupportFragmentManager();
        Fragment MyFragment = (Fragment) manager.getFragment(savedInstanceState, "currentFragment");
        if(MyFragment!=null)
        {
            FragmentTransaction ft=getSupportFragmentManager().beginTransaction();
            ft.replace(R.id.content_frame, MyFragment);
            ft.commit();
        }

    }
        setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.setDrawerListener(toggle);
    toggle.syncState();
    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);
    displayMovieFragments(R.id.nav_popular);
}


protected void onSaveInstanceState(Bundle outState) {
    // Save the values you need into "outState"
    super.onSaveInstanceState(outState);
    manager = getSupportFragmentManager();
    Fragment currentFragment = getSupportFragmentManager().findFragmentById(R.id.content_frame);
    manager.putFragment(outState, "currentFragment", currentFragment);
}

@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        super.onBackPressed();
    }
}

@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
    // Handle navigation view item clicks here.
    displayMovieFragments(item.getItemId());
    return true;
}
private void displayMovieFragments(int itemId)
{
    String actionBarTitle="";
    Fragment fragment=null;
    switch (itemId)
    {
        case R.id.nav_popular:
            fragment=new MostPopular();
            actionBarTitle="Most Popular Movies";
            break;
        case R.id.nav_top_rated:
            fragment=new TopRated();
            actionBarTitle="Top Rated Movies";
            break;
        case R.id.nav_favourite:
            fragment=new FavoriteMovies();
            actionBarTitle="My Favorite Movies";
            break;
    }
    if(fragment!=null)
    {
        FragmentTransaction ft=getSupportFragmentManager().beginTransaction();
        ft.replace(R.id.content_frame, fragment);
        ft.commit();
        getSupportActionBar().setTitle(actionBarTitle);
    }
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
}