颤振 - 在本地访问数据

Question

I have some problem that is very hard to explain... I am building an social media app. I wrote the login page with SharedPreferences and while I am doing this, I posted email and password to an url. The url I posted the datas contains some ID values. When I want to get this id values, flutter gives me error. I will add code and error to below. please help me...

Login Page and post email&password:

PostValuesModel postEmailAndPasswordValuesFromJson(String str) =>
    PostValuesModel.fromJson(json.decode(str));

String postEmailAndPassword(PostValuesModel data) => json.encode(data.toJson());

class PostValuesModel {
  String email;
  String password;
  int servisLogin;
  String servisId;

  PostValuesModel({
    this.email,
    this.password,
    this.servisLogin,
    this.servisId,
  });

  factory PostValuesModel.fromJson(Map<String, dynamic> json) =>
      PostValuesModel(
        email: json["email"],
        password: json["password"],
        servisLogin: json["login"],
        servisId: json["servis_id"],
      );

  Map<String, dynamic> toJson() => {
        "email": email,
        "password": password,
        "login": servisLogin,
        "servis_id": servisId,
      };
}

Future<PostValuesModel> postEmailAndPasswordValues(
  String emailTitle,
  String passwordTitle,
) async {
  final String apiUrl = "https://rsad.com//dart.php";

  final response = await http.post(apiUrl, body: {
    "email": emailTitle,
    "password": passwordTitle,
  });

  if (response.statusCode == 200) {
    final String responseString = response.body;

    return postEmailAndPasswordValuesFromJson(responseString);
  } else {
    print('Error');
  }
}


class _LoginScreenState extends State<LoginScreen> {
  TextEditingController emailController = TextEditingController();
  TextEditingController passwordController = TextEditingController();

  bool isLoggedIn = false;
  String emailSession = '';

  PostValuesModel _email;
  PostValuesModel _password;
  PostValuesModel _servisLogin;
  PostValuesModel _servisId;

Widget _buildLoginButton() {
    Widget _buildChild() {
        return CupertinoButton(
          onPressed: () async {
            final String emailTitle = emailController.text.toString();
            final String passwordTitle = passwordController.text.toString();

            final PostValuesModel user = await postEmailAndPasswordValues(
              emailTitle,
              passwordTitle,
            );

            setState(() {
              _email = user;
              _password = user;
              _servisLogin = user;
              _servisId = user;
            });

            print(_servisId.servisId.toString());

            if (_servisLogin.servisLogin == 0) {
              Navigator.of(context);
            } else {
              Navigator.of(context).push(_routeServisLogin());
            }

            isLoggedIn ? logout() : loginUser();

            //Navigator.of(context).push(_routeLogin());
          },
          padding: EdgeInsets.all(15.0),
          color: Colors.red,
          child: Text(
            'Giriş Yap',
            style: TextStyle(
              color: Colors.white,
            ),
          ),
        );
    }

    return Container(
      padding: EdgeInsets.symmetric(vertical: 25.0),
      width: double.infinity,
      child: _buildChild(),
    );
  }
}

And I want to fetch values to here:

BekliyorModel bekliyorModelFromJson(String str) =>
    BekliyorModel.fromJson(json.decode(str));

String bekliyorModelToJson(BekliyorModel data) => json.encode(data.toJson());

class BekliyorModel {
  String servis_id;
  String kategori;

  BekliyorModel({this.servis_id, this.kategori});

  factory BekliyorModel.fromJson(Map<String, dynamic> json) => BekliyorModel(
        servis_id: json["servis_id"],
        kategori: json["kategori"],
      );

  Map<String, dynamic> toJson() => {
        "servis_id": servis_id,
        "kategori": kategori,
      };
}

Future<BekliyorModel> postAndFetchBekliyorDatas(
  String servisIdTitle,
  String kategoriTitle,
) async {
  final String apiUrl =
      "https://www.rsad.com/dart.php";

  final response = await http.post(apiUrl, body: {
    "kategori": kategoriTitle,
    "servis_id": servisIdTitle,
  });

  if (response.statusCode == 200) {
    final String responseString = response.body;

    return bekliyorModelFromJson(responseString);
  } else {
    return null;
  }
}

class _ServisProfilState extends State<ServisProfil> {
  BekliyorModel _servisId;
  BekliyorModel _kategori;

 Widget _buildBekliyor() {
    return Container(
      height: 60,
      child: RaisedButton(
          highlightElevation: 0,
          splashColor: Colors.transparent,
          elevation: 0,
          color: Colors.white,
          child: Container(
            alignment: Alignment.centerLeft,
            child: Text(
              'Bekliyor/Sonuçlanan',
              style: TextStyle(fontSize: 18, color: Colors.black),
            ),
          ),
          onPressed: () async {
            PostValuesModel deneme;

            final String servisIdTitle = deneme.servisId.toString();
            final String kategoriTitle = 3.toString();

            final BekliyorModel user = await postAndFetchBekliyorDatas(
              kategoriTitle,
              servisIdTitle,
            );

            setState(() {
              _kategori = user;
              _servisId = user;
            });

            print(servisIdTitle.toString());

            // Navigator.of(context).push(
            //   CupertinoPageRoute(
            //     builder: (context) => Bekliyor(),
            //   ),
            // );
          }),
      decoration: BoxDecoration(
        border: Border(
          bottom: BorderSide(
            width: 1,
            color: Colors.black12,
          ),
        ),
      ),
    );
  }
}

it gives me this error:

[VERBOSE-2:ui_dart_state.cc(166)] Unhandled Exception: NoSuchMethodError: The getter 'servisId' was called on null.
Receiver: null
Tried calling: servisId
#0      Object.noSuchMethod  (dart:core-patch/object_patch.dart:51:5)
#1      _ServisProfilState._buildBekliyor.<anonymous closure> 
package:ekspar/Servis/service_profile.dart:116
#2      _InkResponseState._handleTap 
package:flutter/…/material/ink_well.dart:992
#3      _InkResponseState.build.<anonymous closure> 
package:flutter/…/material/ink_well.dart:1098
#4      GestureRecognizer.invokeCallback 
package:flutter/…/gestures/recognizer.dart:184
#5      TapGestureRecognizer.handleTapUp 
package:flutter/…/gestures/tap.dart:524
#6      BaseTapGestureRecognizer._checkUp 
package:flutter/…/gestures/tap.dart:284
#7      BaseTapGestureRecognizer.acceptGesture 
package:flutter/…/gestures/tap.dart:256
#8      GestureArenaManager.sweep 
package:flutter/…/gestures/arena.dart:158
#9      GestureBinding.handleEvent (<…>

I think, here needs to edit:

   final String servisIdTitle = deneme.servisId.toString();

please help me...

Answer 1

It is because of this part of code..

PostValuesModel deneme;
final String servisIdTitle = deneme.servisId.toString();

You just declared the variable deneme in the first line without assigning a value to it, and then in the second line, you are trying to call the getter servisId on it, while your variable deneme is still null, just like the error says.