I am trying to fetch data Using Github API and display it in flutter app but in FutureBuilder snapshot.hasData shows its null and executes snapshot.hasError. I want to display name of repositories from github in a ListView

Can you u help to understand and correct the error.

Here is the code :

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
      
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class Repo {
  String name;
  String htmlUrl;
  //int stargazersCount;
  String description;
  Repo(
      {required this.name,
      required this.htmlUrl,
      //required this.stargazersCount,
      required this.description}
  );

  factory Repo.fromJson(Map<String, dynamic> json) {
    return Repo(
      name: json['name'],
      htmlUrl: json['html_url'],
      //stargazersCount: json['stargazers_count'],
      description: json['description'],
    );
  }
}

class All {
  List<Repo> repos;
  All({required this.repos});
  factory All.fromJson(List<dynamic> json) {
    // ignore: prefer_collection_literals
    List<Repo> repos = List<Repo>.empty(growable: true);
    repos = json.map((r) => Repo.fromJson(r)).toList();
    print(repos);
    return All(repos: repos);
  }
}

Future<All> fetchRepos() async {
  
  
  final response =
      await http.get(Uri.parse('https://api.github.com/users/freeCodeCamp/repos'));

  if (response.statusCode == 200) {
    //print(response.body);
    return All.fromJson(json.decode(response.body));
  } else {
    throw Exception('Failed to Fetch repos!');
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

  late Future<All> futureRepo;
  @override
  void initState() {
    super.initState();
    futureRepo=fetchRepos();
  }

  @override
  Widget build(BuildContext context) {
    
    return Scaffold(
        appBar: AppBar(
        
          title: const Text('Github Repo List'),
        ),
        body: Padding(
          padding: const EdgeInsets.all(8.0),
          child: FutureBuilder<All>(
            future: futureRepo,
            builder: (context, snapshot) {
              
              if (snapshot.hasData) {
                List<Repo> repos = List<Repo>.empty(growable: true);

                for (int i = 0; i < snapshot.data!.repos.length; i  ) {
                  repos.add(
                    Repo(
                      name: snapshot.data!.repos[i].name,
                      htmlUrl: snapshot.data!.repos[i].htmlUrl,
                      // stargazersCount:
                      //     snapshot.data!.repos[i].stargazersCount,
                      description: snapshot.data!.repos[i].htmlUrl,
                    ),
                  );
                }

                return ListView(
                  children: repos.map((r) => Card(
                    child: Column(
                      children: [
                        Text(r.name),
                        Text(r.description),
                        Text(r.htmlUrl),
                        //Text(r.stargazersCount.toString())
                      ],
                    ),
                  )).toList(),
                );
              } else if (snapshot.hasError) {
                print(snapshot.error);
                return const Center(
                  child: Text('Error'),
                );
              } else {
                return const Center(
                  child: CircularProgressIndicator(),
                );
              }
            },
          ),
        )
        
      );
  }
}

while executing snapshot.error it displays the bellow error:

Expected a value of type 'String', but got one of type 'Null'

CodePudding user response：

• The Repo data model is built wrong. They should use Null safe

class Repo {
  String? name;
  String? htmlUrl;
  //int stargazersCount;
  String? description;
  Repo(this.name, this.htmlUrl, this.description);

  factory Repo.fromJson(Map<String, dynamic> json) {
    return Repo(
      json['name'],
      json['html_url'],
      //stargazersCount: json['stargazers_count'],
      json['description'],
    );
  }
}


 return ListView(
                  children: repos
                      .map((r) => Card(
                            child: Column(
                              children: [
                                Text(r.name ?? ''),
                                Text(r.description ?? ''),
                                Text(r.htmlUrl ?? ''),
                                //Text(r.stargazersCount.toString())
                              ],
                            ),
                          ))
                      .toList(),
                );