Flutter Bloc - Flutter Bloc state not updating - flutter

Question

i'm just getting started with flutter bloc.
i try to make state but it always goes to initial. what's the solution?
BLOC
class VisiMisiBloc extends Bloc<VisiMisiEvent, VisiMisiState> {
VisiMisiBloc(this.visiMisiRepository) : super(VisiMisiInitial());
final VisiMisiRepository visiMisiRepository;
#override
Stream<VisiMisiState> mapEventToState(VisiMisiEvent event) async* {
if (event is GetVisiMisiList) {
yield* _getVisiMisi(event, state);
}
}
Stream<VisiMisiState> _getVisiMisi(VisiMisiEvent event, VisiMisiState state) async* {
yield VisiMisiLoading();
try {
ResponseModel<VisiMisiModel> response = await visiMisiRepository.getVisiMisi();
print(response);
if (response.statusCode == 0) {
int insertedId = await visiMisiRepository.insertVisiMisi(response.data);
print(insertedId);
List<VisiMisiModel> visiMisiList = await visiMisiRepository.getAllVisiMisi();
yield VisiMisiLoaded(visiMisiList);
} else {
yield VisiMisiError(response.errorMessage);
}
} on Exception catch (e) {
yield VisiMisiError(e.toString());
}
}
}
STATE
part of 'visi_misi_bloc.dart';
abstract class VisiMisiState extends Equatable {
const VisiMisiState();
}
class VisiMisiInitial extends VisiMisiState {
const VisiMisiInitial();
#override
List<Object>get props => [];
}
class VisiMisiLoading extends VisiMisiState {
const VisiMisiLoading();
#override
List<Object>get props => [];
}
class VisiMisiLoaded extends VisiMisiState {
final List<VisiMisiModel> visiMisiModel;
const VisiMisiLoaded(this.visiMisiModel);
#override
List<Object> get props => [visiMisiModel];
}
class VisiMisiError extends VisiMisiState {
final String message;
const VisiMisiError(this.message);
#override
List<Object>get props => [message];
}
EVENT
part of 'visi_misi_bloc.dart';
abstract class VisiMisiEvent extends Equatable{
const VisiMisiEvent();
}
class GetVisiMisiList extends VisiMisiEvent {
#override
List<Object> get props => [];
}
REPOSITORY
abstract class VisiMisiRepository {
Future<int> insertVisiMisi(VisiMisiModel todo);
Future<ResponseModel<VisiMisiModel>> getVisiMisi();
Future<List<VisiMisiModel>> getAllVisiMisi();
}
REPOSITORY IMPL
class VisiMisiRepositoryImpl extends VisiMisiRepository {
final NetworkInfoImpl networkInfo;
final RemoteDataSource remoteDatasource;
final VisiMisiDao dao;
VisiMisiRepositoryImpl(this.networkInfo, this.remoteDatasource, this.dao);
#override
Future<ResponseModel<VisiMisiModel>> getVisiMisi() {
return remoteDatasource.visiMisi();
}
#override
Future<int> insertVisiMisi(VisiMisiModel todo) {
return dao.upsert(todo);
}
#override
Future<List<VisiMisiModel>> getAllVisiMisi() {
return dao.getAll(userTABLE, VisiMisiModel.fromJson);
}
}
REMOTE DATASOURCE
Future<ResponseModel<VisiMisiModel>> visiMisi() async {
SharedPreferences prefs = await SharedPreferences.getInstance();
String auth_token = prefs.getString("auth_token");
try {
final response = await httpClient.get(ServiceUrl.visiMisi, auth_token);
if(response.statusCode != 200){
throw new Exception('Error getting visi misi');
}
return ResponseModel<VisiMisiModel>.fromJson(response, VisiMisiModel.fromJson);
}catch(e){
print(e);
}
}
VIEW
class VisiMisiPage extends StatefulWidget {
#override
_VisiMisiPageState createState() => _VisiMisiPageState();
}
class _VisiMisiPageState extends State<VisiMisiPage> {
VisiMisiRepository repository;
#override
void initState(){
super.initState();
}
#override
Widget build(BuildContext context) {
return SafeArea(
child: Scaffold(
backgroundColor: AppColor.white,
appBar: AppBar(
title: Text("VISI & MISI", style: TextStyle(fontSize: 16, color: AppColor.deepCerulean),),
backgroundColor: Colors.white,
elevation: 0,
automaticallyImplyLeading: false,
brightness: Brightness.light,
leading: IconButton(
icon: new Icon(Icons.arrow_back, color: AppColor.deepCerulean,),
onPressed: () => Navigator.of(context).pop(),
),
),
body: BlocProvider<VisiMisiBloc>(
create: (_) => VisiMisiBloc(repository),
child: BlocBuilder<VisiMisiBloc, VisiMisiState>(
builder: (context, state) {
if (state is VisiMisiInitial) {
//BlocProvider.of<VisiMisiBloc>(context).add(GetVisiMisiList());
return Center(child: Text(state.toString()),);
} else if (state is VisiMisiLoading) {
return Center(child: CircularProgressIndicator(),);
} else if (state is VisiMisiLoaded) {
return SingleChildScrollView(
child: Container(
child: Column(
mainAxisAlignment: MainAxisAlignment.start,
crossAxisAlignment: CrossAxisAlignment.start,
children: [
_visiWidget(context, state),
SizedBox(height: 20,),
_misiWidget(context),
SizedBox(height: 30,),
_footerWidget(context)
],
),
),
);
} else if (state is VisiMisiError) {
return Center(child: Text(state.message),);
}
}
)
),
)
);
}
void _onWidgetDidBuild(Function callback) {
WidgetsBinding.instance.addPostFrameCallback((_) {
callback();
});
}
}
I get an Unhandled Exception: Unhandled error NoSuchMethodError: The method 'getVisiMisi' was called on null.
in view, the state shows in VisiMisiInitial, and doesn't want to update to VisiMisiLoading

Answer 1

try to initialize the repository like so:
class _VisiMisiPageState extends State<VisiMisiPage> {
VisiMisiRepository repository;
#override
void initState(){
super.initState();
repository = VisiMisiRepositoryImpl( parameters here ); // add this one
}

Answer 2

To initialize repository, you should use RepositoryProvider.
For example, something like that
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MultiRepositoryProvider(
providers: [
RepositoryProvider<UserRepository>(
create: (context) => UserRepository(),
),
],
child: MultiBlocProvider(
providers: [
BlocProvider<LoginBloc>(
create: (context) => LoginBloc(context.read<UserRepository>()),
),
],
child: Widget()));
}
}
Then, it will be automatically initialized

Answer 3

I have analysed your code ,and I found 2 mistakes:
1st. you just created instance of your VisiMisiRepository and not initialised. and you are calling their methods that's why you getting error Unhandled error NoSuchMethodError: The method 'getVisiMisi' was called on null.
2nd. You just initialised your bloc within passing instance of repository, and haven't performed any bloc event . that's why code keep showing initial state.
You might have got your answer.
if not, take help from here it'll surely help you:
replace this:
create: (_) => VisiMisiBloc(repository),
with this:
create: (_) => VisiMisiBloc(VisiMisiRepository())..add(GetVisiMisiList()),
In your widget tree:
body: BlocProvider<VisiMisiBloc>(
create: (_) => VisiMisiBloc(VisiMisiRepository())..add(GetVisiMisiList()), //initialising bloc within repository and hit event as well.
child: BlocBuilder<VisiMisiBloc, VisiMisiState>(
builder: (context, state) {
if (state is VisiMisiInitial) {
return Center(child: Text(state.toString()),);
} else if (state is VisiMisiError) {
return Center(child: Text(state.message),);
} else if (state is VisiMisiLoaded) {
return SingleChildScrollView(
child: Container(
child: Column(
mainAxisAlignment: MainAxisAlignment.start,
crossAxisAlignment: CrossAxisAlignment.start,
children: [
_visiWidget(context, state),
SizedBox(height: 20,),
_misiWidget(context),
SizedBox(height: 30,),
_footerWidget(context)
],
),
),
);
}
return Center(child: CircularProgressIndicator(),);
}
)
),
this answer will also resolve Unhandled error NoSuchMethodError: The method 'getVisiMisi' was called on null error.