am learning api integration with bloc, these exception is been thrown when data is trying to fetch, for loadingstate i assigned a progressindicator then after that state when trying to get data,these exeption is been thrown ,pls helpenter image description here
as per the console i tried to change the data type to from double to num, still same exception
try {
_emitters.add(emitter);
await handler(event as E, emitter);
} catch (error, stackTrace) {
onError(error, stackTrace);
rethrow;
} finally {
onDone();
}
networkfile.dart
class Repository {
List<FakeStore> collections = [];
Future<List<FakeStore>?> getdata() async {
String url = 'https://fakestoreapi.com/products';
final data = await http.Client().get(Uri.parse(url));
if (data.statusCode != 200) {
return null;
} else {
Iterable values = jsonDecode(data.body);
for (var value in values) {
FakeStore fakeStore = FakeStore.fromJson(value);
collections.add(fakeStore);
}
return collections;
}
}
}
bloc.dart
class FakestoreBloc extends Bloc<FakestoreEvent, FakestoreState> {
final Repository repository;
FakestoreBloc({required this.repository}) : super(FakestoreInitialstate()) {
on<FakestoreEvent>((event, emit) async {
if (event is StorelaodEvent) {
emit(Fakestorelaodingstate());
List<FakeStore>? apiresult = await repository.getdata();
if (apiresult == null) {
emit(FAkestoreErrorstate());
} else {
emit(Fakestoreloadedstate(apiresult: apiresult));
}
}
});
}
}
Related
I use flutter to retrieve a document from my firestore database. to do this, I create a DocumentSnapshot type variable which will be passed as a parameter to my getClasseName() function to retrieve the documents. Inside my function the document exists, so I assign it to my variable but my variable remains null when I want to use it
this is a snippet of my code
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
import 'package:ude/model/enseignant.dart';
class DBServices {
static final CollectionReference lyceecol =
FirebaseFirestore.instance.collection('Lycee');
static Future getUser(String? lycee, String? id) async {
try {
final QuerySnapshot<Object?> snapshot = await lyceecol
.doc(lycee)
.collection('Enseignant')
.where('Id', isEqualTo: id)
.get();
final EnseignantM userData = snapshot.docs
.map((QueryDocumentSnapshot<Object?> e) => EnseignantM.fromSnapshot(
e as DocumentSnapshot<Map<String?, dynamic>>))
.single;
return userData;
} catch (e) {
print('ENSEIGNANT NOT FOUND');
print(e);
throw e;
}
}
static Future getClasseName(
String? lycee, String? id, List<String> list) async {
try {
String classeName;
int i = 0;
final snapshot = await lyceecol
.doc(lycee)
.collection('Enseignant')
.doc(id)
.collection('Classes')
.get();
for (var classe in snapshot.docs) {
DocumentReference<Map<String, dynamic>> classeRef =
classe.data()["reference"];
DocumentSnapshot<Map<String, dynamic>>? classRoom;
await DBServices.getClasse(classeRef.path, classRoom);
if (classRoom != null) {
print('CLASSENAME ${classRoom.data()!["Nom"]}');
classeName = classRoom.data()!["Nom"];
list[i] = classeName;
print(list[i]);
i++;
} else {
print('Impossible de charger les classes affilees a cet enseignant');
}
}
} catch (e) {
print(e);
rethrow;
}
}
static Future<void> getClasse(
String? path, DocumentSnapshot<Map<String, dynamic>>? classroom) async {
try {
await FirebaseFirestore.instance.doc(path!).get().then((snapshot) {
if (snapshot.exists) {
classroom = snapshot; //.data()!["Nom"];
} else {
debugPrint("Document not found");
}
});
debugPrint('CLASSROOMMMM: ${classroom!.data()!["Nom"]}');
} catch (e) {
debugPrint('CLASSE Not EXIST');
print(e);
rethrow;
}
}
}
---
/*this is where the problem is*/
static Future getClasseName(
String? lycee, String? id, List<String> list) async {
try {
String classeName;
int i = 0;
final snapshot = await lyceecol
.doc(lycee)
.collection('Enseignant')
.doc(id)
.collection('Classes')
.get();
for (var classe in snapshot.docs) {
DocumentReference<Map<String, dynamic>> classeRef =
classe.data()["reference"];
DocumentSnapshot<Map<String, dynamic>>? classRoom;
await DBServices.getClasse(classeRef.path, classRoom);
if (classRoom != null) {
print('CLASSENAME ${classRoom.data()!["Nom"]}');
classeName = classRoom.data()!["Nom"];
list[i] = classeName;
print(list[i]);
i++;
} else {
print('Impossible de charger les classes affilees a cet enseignant');
}
}
} catch (e) {
print(e);
rethrow;
}
}
static Future<void> getClasse(
String? path, DocumentSnapshot<Map<String, dynamic>>? classroom) async {
try {
await FirebaseFirestore.instance.doc(path!).get().then((snapshot) {
if (snapshot.exists) {
classroom = snapshot; //.data()!["Nom"];
} else {
debugPrint("Document not found");
}
});
debugPrint('CLASSROOMMMM: ${classroom!.data()!["Nom"]}');
} catch (e) {
debugPrint('CLASSE Not EXIST');
print(e);
rethrow;
}
}
I tried not to pass my variable as a parameter and to directly assign the Document returned by the function to it, but it didn't work.
Your help will be invaluable to me
I have a simple flutter code to retrieve some data from Firestore. the data is retireved correctly, however passing the data from the future function making the result always null. can you advise how to adapt the code to return the list?
that is the class where the actual query is happening:
class DatabaseManager {
final CollectionReference BusinessProfilesCollection =
FirebaseFirestore.instance.collection("BusinessProfilesCollection");
Future GetBusinessProfilesCollection() async {
List businessprofileslist = [];
try {
await BusinessProfilesCollection.get().then((QuerySnapshot) {
QuerySnapshot.docs.forEach((element) {
businessprofileslist.add(element.data());
print(businessprofileslist[0]);
});
});
} catch (e) {
print(e.toString());
return null;
}
}
}
here is the page where I am calling the function: (however the result is always null)
class _ProfilesListPageState extends State<ProfilesListPage> {
List businessprofileslist = [];
#override
void initState() {
super.initState();
fetchBusinessProfilesList();
}
fetchBusinessProfilesList() async {
dynamic result = await DatabaseManager().GetBusinessProfilesCollection();
print(result.toString());
if (result == null) {
print('enable to retieve');
} else {
print('success');
setState(() {
businessprofileslist = result;
});
}
}
#override
Widget build(BuildContext context) {
return Scaffold();
}
}
You're not returning anything from GetBusinessProfilesCollection but null, so the result seems somewhat expected.
I guess you want to do:
class DatabaseManager {
final CollectionReference BusinessProfilesCollection =
FirebaseFirestore.instance.collection("BusinessProfilesCollection");
Future GetBusinessProfilesCollection() async {
List businessprofileslist = [];
try {
var QuerySnapshot = await BusinessProfilesCollection.get();
querySnapshot.docs.forEach((element) {
businessprofileslist.add(element.data());
});
return businessprofileslist;
} catch (e) {
print(e.toString());
return null;
}
}
}
Btw: returning null when the load fails, is just going to lead to a null pointer exception when you then do print(result.toString());. So I recommend not catching the error and just letting it bubble up. With that your code can be simplified to:
class DatabaseManager {
final CollectionReference BusinessProfilesCollection =
FirebaseFirestore.instance.collection("BusinessProfilesCollection");
Future GetBusinessProfilesCollection() async {
var QuerySnapshot = await BusinessProfilesCollection.get();
return querySnapshot.docs.map((element) => element.data());
}
}
You just need to return the list
return businessprofileslist;
CODE :
class DatabaseManager {
final CollectionReference BusinessProfilesCollection =
FirebaseFirestore.instance.collection("BusinessProfilesCollection");
Future GetBusinessProfilesCollection() async {
List businessprofileslist = [];
try {
await BusinessProfilesCollection.get().then((QuerySnapshot) {
QuerySnapshot.docs.forEach((element) {
businessprofileslist.add(element.data());
print(businessprofileslist[0]);
});
// you just need to return the list here after filling it up
return businessprofileslist;
});
} catch (e) {
print(e.toString());
return null;
}
}
}
Code with a little improvement:
class DatabaseManager {
final CollectionReference BusinessProfilesCollection =
FirebaseFirestore.instance.collection("BusinessProfilesCollection");
Future GetBusinessProfilesCollection() async {
await BusinessProfilesCollection.get().then((QuerySnapshot) {
QuerySnapshot.docs.map((doc) => doc.data()).toList();
});
}
}
Try that with calling the function in feching
fetchBusinessProfilesList()
async {
dynamic result ;
await DatabaseManager().GetBusinessProfilesCollection().then((value){
result=value;
print(result.toString());
if (result == null) {
print('enable to retieve');
} else {
print('success');
setState(() {
businessprofileslist = result;
});
}
});
}
I was studying with an AWS tutorial however, that tutorial is not null safety.
I'v tried to convert it, but is showing:
LateInitializationError: Field '_credentials#26120019' has not been initialized.
I think that "late" modifier is not initializing the variables when I try to get the values in verifyCode
Pleease, how can I fix the code below
enum AuthFlowStatus {login, signUp, verification, session}
class AuthState {
final AuthFlowStatus? authFlowStatus;
AuthState({this.authFlowStatus});
}
class AuthService {
final authStateController = StreamController<AuthState>();
late AuthCredentials _credentials;
void showSignUp() {
final state = AuthState(authFlowStatus: AuthFlowStatus.signUp);
authStateController.add(state);
}
void showLogin() {
final state = AuthState(authFlowStatus: AuthFlowStatus.login);
authStateController.add(state);
}
void loginWithCredentials(AuthCredentials credentials) async {
try {
final result = await Amplify.Auth.signIn(
username: credentials.username, password: credentials.password,
);
if (result.isSignedIn) {
final state = AuthState(authFlowStatus: AuthFlowStatus.session);
authStateController.add(state);
} else {
print('User could not be signed in');
}
} on AuthException catch (authError) {
print('Could not login - ${authError}');
}
}
void signUpWithCredentials(SignUpCredentials credentials) async {
try {
Map<CognitoUserAttributeKey, String> userAttributes = {
CognitoUserAttributeKey.email: credentials.email,
};
final result = await Amplify.Auth.signUp(
username: credentials.username,
password: credentials.password,
options: CognitoSignUpOptions(
userAttributes: userAttributes
),
);
if (result.isSignUpComplete) {
loginWithCredentials(credentials);
} else {
this._credentials = credentials;
}
final state = AuthState(authFlowStatus: AuthFlowStatus.verification);
authStateController.add(state);
} on AmplifyException catch (authError) {
print('Failed ro sign up - ${authError}');
}
}
void verifyCode(String verificationCode) async {
try {
final result = await Amplify.Auth.confirmSignUp(
username: _credentials.username,
confirmationCode: verificationCode,
);
if (result.isSignUpComplete) {
loginWithCredentials(_credentials);
} else {
//not implemented yet
}
} on AuthException catch (authError) {
print('Could not verify code - ${authError}');
}
}
}
I working on error handling of api's. i want if api is crashed then it display a message of "Server is down" something like this, in UI.
I created a class where i'm creating methods of api, here in getBooks method if i modify the api url then it is printing this Exception, and i want it in UI. The problem is getBooks return type is List<Book>> so we can't return this Exception, any solution how to do this?
Exception
E/flutter (12924): [ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: Exception
here is my api code
class BooksApi {
static Future<List<Book>> getBooks(String query) async {
try {
final url = Uri.parse(
'https://gist.githubusercontent.com/JohannesMilke/d53fbbe9a1b7e7ca2645db13b995dc6f/raw/eace0e20f86cdde3352b2d92f699b6e9dedd8c70/books.json');
final response = await http.get(url);
if (response.statusCode == 200) {
final List books = json.decode(response.body);
return books.map((json) => Book.fromJson(json)).where((book) {
final titleLower = book.title.toLowerCase();
final authorLower = book.author.toLowerCase();
final searchLower = query.toLowerCase();
return titleLower.contains(searchLower) ||
authorLower.contains(searchLower);
}).toList();
} else {
throw Exception;
}
} catch (e) {
print("e");
print(e);
}
throw Exception;
}
}
and calling it like
Future init() async {
setState(() {
isLoading = true;
});
var books = await BooksApi.getBooks(query); //this
var response = await obj.getProduct();
print(response);
setState(() => this.books = books);
setState(() {
isLoading = false;
});
}
You could handle errors with then and onError :
await BooksApi.getBooks(query).then((books) async {
setState(() => {
this.books = books;
this.isLoading = false;
})
}, onError: (error) {
// do something with error
});
or a simple try-catch (you can write try-catch clauses the same way you would in synchronous code).
See handling errors.
You can also use catchError id you don't use async/await :
BooksApi.getBooks(query).then((books) {
setState(() => {
this.books = books;
this.isLoading = false;
})
}).catchError((error, stackTrace) {
print("error is: $error");
});
See futures error handling.
Try to wrap 'var books = await BooksApi.getBooks(query)' with try and catch.
...
try {
var books = await BooksApi.getBooks(query);
} catch (e) {
// To do for UI
}
...
For api, you need to make something like this:
APIModel{
final int code;
// or a success flag
// final bool success;
final String message;
final List<Book> data;
APIModel({this.code,this.message,this.data});
}
It means, every api have its own code,message,and data filed.
When you request, you can check your code or success:
var response = await request(params);
isLoading = false;
if(response.code == 0){}
// or
if(response.success){
// do what you want
}
else {
Toast.show(response.message);
}
You can use build_runner and json_serializable.
How to transfer data from one screen to another using bloc and save , I would like to create a user profile where I have two screens, two steps to creating a profile. I created two blocs for each class, in one I have an avatar, city and name, in the other only description. I used an amplify and when I save the first screen and when I go to the second one, delete the data from the first screen. How do I save everything? without delete? after save second screen.
First screen:
class ProfileBloc extends Bloc<ProfileEvent, ProfileState> {
final DataRepository dataRepo;
final StorageRepository storageRepo;
final _picker = ImagePicker();
ProfileBloc(
{User? user,
required bool isCurrentUser,
required this.storageRepo,
required this.dataRepo})
: super(ProfileState(user: user, isCurrentUser: isCurrentUser)) {
// storageRepo
// .getUrlForFile(user!.avatarKey)
// .then((url) => add(ProvideImagePath(avatarPath: url)));
ImageUrlCache.instance
.getUrl(user!.avatarKey)
.then((url) => add(ProvideImagePath(avatarPath: url)));
}
#override
Stream<ProfileState> mapEventToState(ProfileEvent event) async* {
if (event is ChangeAvatarRequest) {
yield state.copyWith(isImageSourceActionSheetVisible: true);
} else if (event is OpenImagePicker) {
yield state.copyWith(isImageSourceActionSheetVisible: false);
try {
final selectedImage =
await _picker.pickImage(source: event.imageSource);
if (selectedImage == null) return;
final imageKey = await storageRepo.uploadFile(File(selectedImage.path));
final user = state.user!.copyWith(avatarKey: imageKey);
String? imageUrl;
await Future.wait<void>([
dataRepo.updateUser(user),
storageRepo.getUrlForFile(imageKey).then((value) => imageUrl = value)
]);
yield state.copyWith(avatarPath: imageUrl);
} catch (e) {
throw e;
}
} else if (event is ProvideImagePath) {
if (event.avatarPath != null)
yield state.copyWith(avatarPath: event.avatarPath);
} else if (event is ProfileCityChanged) {
yield state.copyWith(userCity: event.city);
} else if (event is ProfileNameChanged) {
yield state.copyWith(userName1: event.name);
} else if (event is SaveProfileChanges) {
// handle save changes
yield state.copyWith(formStatus: FormSubmitting());
final updatedUser2 =
state.user!.copyWith(city: state.userCity, name: state.userName1);
try {
await dataRepo.updateUser(updatedUser2);
print(updatedUser2);
yield state.copyWith(formStatus: SubmissionSuccess());
} on Exception catch (e) {
yield state.copyWith(formStatus: SubmissionFailed(e));
} catch (e) {
print(e);
}
}
}
}
Second screen:
class Profile2Bloc extends Bloc<Profile2Event, Profile2State> {
final DataRepository dataRepo;
// User? user;
// String ?get userCity => user!.city;
// String? get userName1 => user!.name;
Profile2Bloc(
{User? user, required bool isCurrentUser, required this.dataRepo})
: super(Profile2State(user: user, isCurrentUser: isCurrentUser));
#override
Stream<Profile2State> mapEventToState(Profile2Event event) async* {
if (event is ProfileDescriptionChanged) {
yield state.copyWith(userDescription: event.description);
} else if (event is SaveProfile2Changes) {
yield state.copyWith(formStatus: FormSubmitting());
final updatedUser =
state.user!.copyWith(description: state.userDescription);
try {
await dataRepo.updateUser(updatedUser);
print(updatedUser);
// print(userDescribe);
yield state.copyWith(formStatus: SubmissionSuccess());
} on Exception catch (e) {
yield state.copyWith(formStatus: SubmissionFailed(e));
} catch (e) {
print(e);
}
}
}
}
Data Repo:
Future<User> updateUser(User updatedUser) async {
try {
await Amplify.DataStore.save(updatedUser);
return updatedUser;
} catch (e) {
throw e;
}
}