Manage state of one page from another class

I'm building an app for training in Flutter and I'm actually stuck in the filter functionality.

I have a ListView where I fetch data from TheMovieDB API and a ModalBottomSheet with three FilterChips for selecting the filter criteria (popular, top rated and latest movies).

And here's where I'm stuck. I want to call the "_loadNextPage()" method when the user presses the "Done" button in the ModalBottomSheet through "performUpdate()" but I can't do it because they're not in the same class.

I'll post the code down below for better understanding.

class _HomePageState extends State<HomePage> {
  RequestProvider _requestProvider = new RequestProvider();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("FluttieDB"),
        actions: <Widget>[
          IconButton(
            icon: Icon(Icons.filter_list),
            onPressed: () => buildFilterBottomSheet(),
          )
        ],
      ),
      body: MovieList(_requestProvider, _currentFilter),
    );
  }

  void buildFilterBottomSheet() {
    showModalBottomSheet(
        context: context,
        builder: (builder) {
          return Container(
            height: 150.0,
            decoration: BoxDecoration(color: Colors.white),
            child: Column(
              children: <Widget>[
                buildFilterTitle(context),
                Expanded(
                  child: _FilterChipRow(),
                ),
              ],
            ),
          );
        });
  }

  Widget buildFilterTitle(BuildContext context) {
    return Container(
      padding: const EdgeInsets.symmetric(horizontal: 12.0, vertical: 6.0),
      alignment: Alignment.centerLeft,
      height: 46.0,
      decoration: BoxDecoration(color: Colors.blue),
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceBetween,
        mainAxisSize: MainAxisSize.max,
        children: <Widget>[
          Text(
            "Filter by",
            style: TextStyle(color: Colors.white, fontSize: 20.0),
          ),
          OutlineButton(
            onPressed: () => performUpdate(context),
            padding: const EdgeInsets.all(0.0),
            shape: const StadiumBorder(),
            child: Text(
              "Done",
              style: TextStyle(color: Colors.white),
            ),
          ),
        ],
      ),
    );
  }

  void performUpdate(BuildContext context) {
    MovieList _movieList = new MovieList(_requestProvider, _currentFilter);
    _movieList.createState()._loadNextPage();
    Navigator.pop(context);
  }
}



class MovieList extends StatefulWidget {
  MovieList(this.provider, this.currentFilter, {Key key}) : super(key: key);

  final RequestProvider provider;
  final String currentFilter;

  @override
  _MovieListState createState() => new _MovieListState();
}

class _MovieListState extends State<MovieList> {
  List<Movie> _movies = List();
  int _pageNumber = 1;
  LoadingState _loadingState = LoadingState.LOADING;
  bool _isLoading = false;

  _loadNextPage() async {
    _isLoading = true;

    try {
      var nextMovies = await widget.provider
          .provideMedia(widget.currentFilter, page: _pageNumber);

      setState(() {
        _loadingState = LoadingState.DONE;
        _movies.addAll(nextMovies);
        _isLoading = false;
        _pageNumber++;
      });
    } catch (e) {
      _isLoading = false;

      if (_loadingState == LoadingState.LOADING) {
        setState(() => _loadingState = LoadingState.ERROR);
      }
    }
  }

  @override
  void initState() {
    super.initState();
    _loadNextPage();
  }

  @override
  Widget build(BuildContext context) {
    switch (_loadingState) {
      case LoadingState.DONE:
        return ListView.builder(
            itemCount: _movies.length,
            itemBuilder: (BuildContext context, int index) {
              if (!_isLoading && index > (_movies.length * 0.7)) {
                _loadNextPage();
              }

              return MovieListItem(_movies[index]);
            });
      case LoadingState.ERROR:
        return Center(
            child: Text("Error retrieving movies, check your connection"));
      case LoadingState.LOADING:
        return Center(child: CircularProgressIndicator());
      default:
        return Container();
    }
  }
}

As you can see, I did some experiments in the performUpdate() but it doesn't refresh the ListView with the selected option in the filters and I don't think it's the best way to achieve what I want.

Thanks and sorry if the question is a bit dumb. I'm a little bit newbie in Flutter.