The getter 'state' was called on null.

address_form.dart

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:pdm_mobile/blocs/account/account_bloc.dart';
import 'package:pdm_mobile/blocs/account/account_event.dart';
import 'package:pdm_mobile/blocs/account/account_state.dart';
import 'package:pdm_mobile/blocs/territory/territory.dart';
import 'package:pdm_mobile/models/account.dart';
import 'package:pdm_mobile/util/error_util.dart';
import 'package:pdm_mobile/widgets/exception/exception_info_view.dart';
import 'package:pdm_mobile/widgets/territory/territory_dropdown_view.dart';

class ChangeAddressForm extends StatefulWidget {
  final AccountBloc accountBloc;
  final Account account;
  ChangeAddressForm(this.accountBloc, this.account, {Key key})
      : super(key: key);

  @override
  State<ChangeAddressForm> createState() =>
      _ChangeAddressWidgetState(accountBloc, account);
}

class _ChangeAddressWidgetState extends State<ChangeAddressForm> {
  final _formKey = GlobalKey<FormState>();
  final _addressController = TextEditingController();
  final _nameController = TextEditingController();
  final _phoneController = TextEditingController();
  final _provinceController = TextEditingController();
  final _regencyController = TextEditingController();
  final _subDistrictController = TextEditingController();
  final _villageController = TextEditingController();
  final AccountBloc accountBloc;
  Account account;
  String _errorInfo = "";
  bool _isFieldError = false;
  bool _inProgress = false;
  StreamSubscription subs;
  Map<String, String> territory = Map();

  _ChangeAddressWidgetState(this.accountBloc, this.account) {
    subs = accountBloc.state.listen((AccountState state) {
      print("Print state =>> $state");
      if (state is AccountUpdated) {
        Navigator.pop(context, true);
      } else if (state is AddressFieldError) {
        print("AddressFieldError");
        setState(() {
          _errorInfo = state.error;
          _isFieldError = true;
        });
      } else if (state is AddressFailure) {
        Scaffold.of(context).showSnackBar(
          SnackBar(
            content: Text(state.error),
            backgroundColor: Colors.red,
          ),
        );
      }
    });
  }

  @override
  void dispose() {
    super.dispose();
    subs.cancel();
  }

  @override
  Widget build(BuildContext context) {
    disableApiErrorHandler();

    _onAddressButtonPressed() {
      if (_formKey.currentState.validate()) {
        accountBloc.dispatch(UpdateAddress(
         name: _nameController.text,
         address: _addressController.text,
         phone: _phoneController.text,
         province: _provinceController.text,
         district: _regencyController.text,
         subDistrict: _subDistrictController.text,
         village: _villageController.text,
        ));
      }
    }

    return BlocBuilder<TerritoryBloc, TerritoryState>(
      builder: (context, state) {
        return Center(
          child: ListView(
            children: <Widget>[
              Padding(
                padding: EdgeInsets.all(10.0),
                child: Form(
                  key: _formKey,
                  child: Column(
                    children: <Widget>[
                      TerritoryDropdownView(
                        onSelectTerritory: (value, type) {
                          switch (type) {
                            case TerritoryType.province:
                              _provinceController.text = value.name;
                              break;
                            case TerritoryType.district:
                              _regencyController.text = value.name;
                              break;
                            case TerritoryType.subDistrict:
                              _subDistrictController.text = value.name;
                              break;
                            case TerritoryType.village:
                              _villageController.text = value.name;
                          }
                        },
                        territory: territory ?? Map(),
                      ),
                      TextFormField(
                        decoration: InputDecoration(labelText: "Nama Lengkap:"),
                        autofocus: true,
                        controller: _nameController,
                      ),
                      TextFormField(
                        decoration: InputDecoration(labelText: "Alamat:"),
                        autofocus: true,
                        controller: _addressController,
                      ),
                      TextFormField(
                        decoration: InputDecoration(labelText: "Nomor Ponsel:"),
                        autofocus: true,
                        controller: _phoneController,
                      ),
                      Container(
                        margin: EdgeInsets.only(top: 16.0, bottom: 16.0),
                        child: Visibility(
                          visible: _isFieldError,
                          child: ExceptionInfoView(
                            title: "Terjadi kesalahan",
                            info: _errorInfo,
                          ),
                        ),
                      ),
                      Row(
                        mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                        children: <Widget>[
                          Padding(
                            padding: EdgeInsets.only(top: 30.0, bottom: 20.0),
                            child: ButtonTheme(
                              // minWidth: MediaQuery.of(context).size.width,
                              child: RaisedButton(
                                  onPressed: !_inProgress
                                      ? _onAddressButtonPressed()
                                      : null,
                                  child: new Text(
                                    "Batalkan",
                                    style: TextStyle(color: Colors.grey),
                                  ),
                                  shape: new RoundedRectangleBorder(
                                      side: BorderSide(color: Colors.grey)),
                                  color: Colors.white),
                            ),
                          ),
                          Padding(
                            padding: EdgeInsets.only(top: 30.0, bottom: 20.0),
                            child: ButtonTheme(
                              // minWidth: MediaQuery.of(context).size.width,
                              child: RaisedButton(
                                onPressed: () =>
                                    Navigator.of(context).push(null),
                                child: new Text(
                                  "Simpan",
                                  style: TextStyle(color: Colors.white),
                                ),
                                shape: new RoundedRectangleBorder(
                                    side: BorderSide(color: Color(0xff039fc0))),
                                color: Color(0xff039fc0),
                              ),
                            ),
                          ),
                        ],
                      ),
                    ],
                  ),
                ),
              ),
            ],
          ),
        );
      },
    );
  }
}