[英]Flutter Bloc - Flutter Bloc state not updating
我刚刚开始使用 flutter 集团。 我尝试制作 state 但它总是进入初始状态。 有什么解决办法?
集团
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];
}
事件
part of 'visi_misi_bloc.dart';
abstract class VisiMisiEvent extends Equatable{
const VisiMisiEvent();
}
class GetVisiMisiList extends VisiMisiEvent {
@override
List<Object> get props => [];
}
存储库
abstract class VisiMisiRepository {
Future<int> insertVisiMisi(VisiMisiModel todo);
Future<ResponseModel<VisiMisiModel>> getVisiMisi();
Future<List<VisiMisiModel>> getAllVisiMisi();
}
存储库实施
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);
}
}
远程数据源
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);
}
}
看法
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();
});
}
}
我收到未处理的异常:未处理的错误 NoSuchMethodError:在 null 上调用了方法“getVisiMisi”。
在视图中,state 显示在 VisiMisiInitial 中,并且不想更新到 VisiMisiLoading
尝试像这样初始化存储库:
class _VisiMisiPageState extends State<VisiMisiPage> {
VisiMisiRepository repository;
@override
void initState(){
super.initState();
repository = VisiMisiRepositoryImpl( parameters here ); // add this one
}
要初始化存储库,您应该使用 RepositoryProvider。
例如,类似的东西
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()));
}
}
然后会自动初始化
我分析了你的代码,发现了两个错误:
第一个。 您刚刚创建了 VisiMisiRepository 的实例并且没有初始化。 并且您正在调用他们的方法,这就是为什么您收到错误Unhandled error NoSuchMethodError: The method 'getVisiMisi' was called on null.
第二。 您刚刚在传递的存储库实例中初始化了您的 bloc,并且没有执行任何 bloc 事件。 这就是代码一直显示初始 state 的原因。
你可能已经得到了答案。 如果没有,请从这里获取帮助,它肯定会对您有所帮助:
替换这个:
create: (_) => VisiMisiBloc(repository),
有了这个:
create: (_) => VisiMisiBloc(VisiMisiRepository())..add(GetVisiMisiList()),
在您的小部件树中:
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(),);
}
)
),
此答案还将解决Unhandled error NoSuchMethodError: The method 'getVisiMisi' was called on null
错误。
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