آموزش استفاده از Rxdart در وب سرویس

  provider: ^4.0.2
  rxdart: ^0.23.1
  bloc: ^3.0.0
  dio: ^3.0.9

  characters: ^1.0.0

https://jsonplaceholder.typicode.com/todos

class Todos {


  final int id, userId;
  final String title;

  Todos(this.id, this.userId, this.title);


  Todos.fromJson(Map<String, dynamic> json)
      :
        id = json["id"],
        userId = json["userId"],
        title = json["title"];

}

class TodosResponse{

  final List<Todos> todos;
  final String error;

  TodosResponse(this.todos, this.error);

  TodosResponse.fromJson(List<dynamic> json):

      todos = (json as List).map((e) => new Todos.fromJson(e)).toList(),
  error = "";


  TodosResponse.withError(String errorValue):
      todos = List(),
  error = errorValue;
}

class TodoRepository{


  final Dio _dio = Dio();

  Future<TodosResponse> getTodos() async{

    var url = "https://jsonplaceholder.typicode.com/todos";
    try{
      Response response = await _dio.get(url);
      return TodosResponse.fromJson(response.data);
    } catch(error,stack){
      print("Exception: $error");
      return TodosResponse.withError("$error");
    }
  }
}

class TodosBloc{
  final TodoRepository _repository = TodoRepository();
      final BehaviorSubject<TodosResponse> _subject =
          BehaviorSubject<TodosResponse>();



      getTodos() async{
         TodosResponse response = await _repository.getTodos();
         _subject.sink.add(response);
      }

      void drainStream(){_subject.value = null; }

      @mustCallSuper
      void dispose() async{
        await _subject.drain();
        _subject.close();
      }

      BehaviorSubject<TodosResponse> get subject => _subject;


}

final todosbloc = TodosBloc();

class TodosHome extends StatefulWidget {
  @override
  _TodosHomeState createState() => _TodosHomeState();
}

class _TodosHomeState extends State<TodosHome> {


  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    todosbloc.getTodos();
  }

  @override
  Widget build(BuildContext context) {
    return StreamBuilder(
      stream: todosbloc.subject.stream,
      builder: (context,AsyncSnapshot<TodosResponse> snapshot){

        if(snapshot.hasData){

            if(snapshot.data.error != null && snapshot.data.error.length >0){
              return _buildErrorWidget(snapshot.data.error);
            }
            return Container(
              height: 700.0,
              child: _buildHomdeWidget(snapshot.data,context),
            );


        } else if ( snapshot.hasError){
          return _buildErrorWidget(snapshot.data.error);
        }
        else{
          return _buildLoadingWidget();
        }
      },
    );
  }


  Widget _buildHomdeWidget(TodosResponse data, var context){


    List<Todos> todoslit = data.todos;

    if(todoslit.length==0){
      return Container(
        width: MediaQuery.of(context).size.width,
        child: Column(

          children: [
            Text("No More Todos....")
          ],
        ),
      );
    }else{
      return Center(
        child:  ListView.builder(

          scrollDirection: Axis.vertical,
          shrinkWrap: true,
          itemCount: todoslit.length,
          itemBuilder: (context,index){

            return Container(
              child: Text(todoslit[index].title),
              margin:  const EdgeInsets.all( 10.0),
            );
          },
        ),
      );
    }
  }


  Widget _buildErrorWidget(String error){

    return Center(
      child: Column(
        children: [
          Text("Error...")
        ],
      ),
    );
  }

  Widget _buildLoadingWidget(){

    return Center(
      child:  Column(
        children: [
          SizedBox(
            height: 25.0,
            width: 25.0,
            child: CircularProgressIndicator(

              valueColor: new AlwaysStoppedAnimation<Color>(Colors.red)
              ,
              strokeWidth: 4.0,
            ),
          )
        ],
      ),
    );
  }

}