我该如何解决这个错误？ 'NoSuchMethodError' 在 null 上调用了方法 '[]'。 接收器：null。 尝试调用：[]("title")

Question

When i run this app, i get this mistake 'NoSuchMethodError' The method '[]' was called on null. Receiver: null. Tried Calling: . I've tried different ways but it didn't worked and i didn´t found solutions on the internet, i'm new at flutter and i'm trying to learn, Do you know who to make it work? Thank you!

import 'package:dio/dio.dart';
import 'package:flutter/material.dart';


class HomeScreen extends StatefulWidget {
  @override
  _HomeScreenState createState() => _HomeScreenState();
}

class _HomeScreenState extends State<HomeScreen> {
//Step 3
  _HomeScreenState() {
    _filter.addListener(() {
      if (_filter.text.isEmpty) {
        setState(() {
          _searchText = "";
          filteredNames = titulos;
        });
      } else {
        setState(() {
          _searchText = _filter.text;
        });
      }
    });
  }

//Step 1
  final TextEditingController _filter = new TextEditingController();
  final dio = new Dio(); // for http requests
  String _searchText = "";
  List titulos = new List(); // titulos we get from API
  List filteredNames = new List(); // names filtered by search text
  Icon _searchIcon = new Icon(Icons.search);
  Widget _appBarTitle = new Text('Search Example');

  //step 2.1
  void _getNames() async {
    final response = await dio.get(
        'https://api.themoviedb.org/3/movie/popular?api_key=0e685fd77fb3d76874a3ac26e0db8a4b&language=en-US&page=1');
    print(response.data);
    List tempList = new List();
    for (int i = 0; i < response.data.length; i++) {
      tempList.add(response.data[i]);
    }
    setState(() {
      titulos = tempList;
      filteredNames = titulos;
    });
  }

//Step 2.2
  void _searchPressed() {
    setState(() {
      if (this._searchIcon.icon == Icons.search) {
        this._searchIcon = new Icon(Icons.close);
        this._appBarTitle = new TextField(
          controller: _filter,
          decoration: new InputDecoration(
              prefixIcon: new Icon(Icons.search), hintText: 'Search...'),
        );
      } else {
        this._searchIcon = new Icon(Icons.search);
        this._appBarTitle = new Text('Search a movie');
        filteredNames = titulos;
        _filter.clear();
      }
    });
  }

  //Step 4
  Widget _buildList() {
    if (!(_searchText.isEmpty)) {
      List tempList = new List();
      for (int i = 0; i < filteredNames.length; i++) {
        if (filteredNames[i]['title']
            .toLowerCase()
            .contains(_searchText.toLowerCase())) {
          tempList.add(filteredNames[i]);
        }
      }
      filteredNames = tempList;
    }
    return ListView.builder(
      itemCount: titulos == null ? 0 : filteredNames.length,
      itemBuilder: (BuildContext context, int index) {
        return new ListTile(
          title: Text(filteredNames[index]['title']),
          onTap: () => print(filteredNames[index]['title']),
        );
      },
    );
  }

  //STep6
  Widget _buildBar(BuildContext context) {
    return new AppBar(
      centerTitle: true,
      title: _appBarTitle,
      leading: new IconButton(
        icon: _searchIcon,
        onPressed: _searchPressed,
      ),
    );
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: _buildBar(context),
      body: Container(
        child: _buildList(),
      ),
      resizeToAvoidBottomPadding: false,
    );
  }
}

Answer 1

I'm new to Dart and this is my first answer here, but maybe what you're trying to get the index of is null. For example if myVariable was null, myVariable[1] or myVariable['propertyname'] can't be accessed.
I think instead, you can use myVariable?['propertyname'] , which will return null if myVariable itself is null, so no errors are thrown. Alternatively, you could check your program flow and ensure that the variable in question is not null when you use it.

(Apologies if this was a bad answer, I'm new here)
(Please take my words with a grain of salt. I'm trying to answer the best I can but I certainly might be wrong.)