Unhandled Exception: Bad state: Cannot add new events after calling close? - flutter

Question

I'm making a login feature, I'm making fire responses to find out whether responses were successful or failed. can see my BLOC coding. the login process was successful but when I want to return to the login page after logging out the error appears Unhandled Exception: Bad state: Cannot add new events after calling close. how can I handle it?
API RESPONSES :
class ApiResponse<T> {
Status status;
T data;
String message;
ApiResponse.loading(this.message) : status = Status.LOADING;
ApiResponse.completed(this.data) : status = Status.COMPLETED;
ApiResponse.error(this.message) : status = Status.ERROR;
// #override
// String toString() {
// return "Status : $status \n Message : $message \n Data : $data";
// }
}
enum Status { LOADING, COMPLETED, ERROR }
BLOC :
class LoginBloc extends Object with Validators{
final _repository = EresidenceRepository();
final _userid = BehaviorSubject<String>();
final _password = BehaviorSubject<String>();
final _imei = BehaviorSubject<String>();
final _coordinate = BehaviorSubject<String>();
final BehaviorSubject<ApiResponse<login_responses>> _subject = BehaviorSubject<ApiResponse<login_responses>>();
Function(String) get userid => _userid.sink.add;
Function(String) get password => _password.sink.add;
Function(String) get imei => _imei.sink.add;
Function(String) get coordinate => _coordinate.sink.add;
Stream<String> get useridValidation => _userid.stream.transform(useridValidator);
Stream<String> get passwordValidation => _password.stream.transform(passwordValidator);
Stream<bool> get submitCheck => Rx.combineLatest2(useridValidation, passwordValidation, (e,p) => true);
login() async {
_subject.sink.add(ApiResponse.loading("Logging In..."));
try {
login_responses response = await _repository.login(
_userid.value, _password.value, _imei.value, _coordinate.value);
prefsBloc.changePrefsLogin(
PrefsState(false, response.data.userid, response.data.password, _imei.value, _coordinate.value, "")
);
_subject.sink.add(ApiResponse.completed(response));
print(response);
} catch (e) {
_subject.sink.add(ApiResponse.error(e.toString()));
print(e);
}
}
dispose(){
_userid.close();
_password.close();
_imei.close();
_coordinate.close();
_subject.close();
}
BehaviorSubject<ApiResponse<login_responses>> get subject => _subject;
}
final login = LoginBloc();
UI :
class LoginPage extends StatefulWidget {
#override
_LoginPageState createState() => _LoginPageState();
}
class _LoginPageState extends State<LoginPage> with WidgetsBindingObserver{
final GlobalKey<ScaffoldState> _scaffoldKey = new GlobalKey<ScaffoldState>();
FocusNode passwordFocusNode, useridFocusNode;
#override
void initState() {
super.initState();
prefsBloc.checkLoginPref(context);
WidgetsBinding.instance.addObserver(this);
}
#override
void dispose() {
WidgetsBinding.instance.removeObserver(this);
super.dispose();
}
#override
Widget build(BuildContext context) {
return AnnotatedRegion<SystemUiOverlayStyle>(
value: SystemUiOverlayStyle.dark,
child: Scaffold(
backgroundColor: Colors.white,
body: StreamBuilder(
stream: login.subject,
builder: (context, AsyncSnapshot<ApiResponse<login_responses>> snapshot){
if(snapshot.hasData) {
print(snapshot.data.status);
switch (snapshot.data.status) {
case Status.LOADING:
_onWidgetDidBuild((){
Scaffold.of(context).showSnackBar(
SnackBar(
content: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: [
Text(snapshot.data.message),
CircularProgressIndicator(),
],
),
backgroundColor: Colors.black,
),
);
});
break;
case Status.COMPLETED:
login_responses result = snapshot.data.data;
if(result.data.bit70 == "000") {
_onWidgetDidBuild((){
login.dispose();
AppRoutes.replace(context, LoginVerifyPage());
});
}else{
_onWidgetDidBuild((){
login.dispose();
AppRoutes.replace(context, MainApp());
});
}
break;
case Status.ERROR:
_onWidgetDidBuild(() {
Scaffold.of(context).showSnackBar(SnackBar(
content: Text('${snapshot.data.message}'),
backgroundColor: Colors.red,
));
});
break;
}
}
return _formLogin();
}
),
)
);
}
_formLogin() {
return SafeArea(
child: Container(
child: Column(
children: <Widget>[
Expanded(
flex: 1,
child: Container(
padding: EdgeInsets.symmetric(horizontal: SizeConfig.widthMultiplier * 1, vertical: SizeConfig.heightMultiplier * 1),
child: CachedNetworkImage(
imageUrl: "https://images.glints.com/unsafe/1024x0/glints-dashboard.s3.amazonaws.com/company-logo/68545821966f833d182f98775c73c7ae.png",
errorWidget: (context, url, error) => Icon(Icons.broken_image),
fit: BoxFit.fill,
),
)
),
Expanded(
flex: 2,
child: Container(
padding: EdgeInsets.all(SizeConfig.heightMultiplier * 2),
child: Column(
children: <Widget>[
Container(
child: StreamBuilder<String>(
stream: login.useridValidation,
builder: (context, snapshot) => DataTextField(
errorText: snapshot.error,
hintText: "No Handphone",
textInputAction: TextInputAction.next,
icon: Icons.phone,
onSubmitted: () => FocusScope.of(context).requestFocus(passwordFocusNode),
onChanged: login.userid,
keyboardType: TextInputType.numberWithOptions(signed: true, decimal: true),
),
)
),
Container(
margin: EdgeInsets.only(top: SizeConfig.heightMultiplier * 2),
child: StreamBuilder<String>(
stream: login.passwordValidation,
builder: (context, snapshot) => PasswordTextField(
errorText: snapshot.error,
hintText: "Password",
textInputAction: TextInputAction.done,
onSubmitted: () {
FocusScope.of(context).requestFocus(FocusNode());
},
onChanged: login.password,
focusNode: passwordFocusNode,
),
)
),
Container(
width: SizeConfig.screenWidth,
margin: EdgeInsets.only(top: SizeConfig.heightMultiplier * 2.5),
child: GestureDetector(
onTap: () => AppRoutes.push(context, ForgotPasswordPage()),
child: Text(
Strings.titleForgotPass+" ?",
style: AppTheme.styleSubTitlePurpel,
textAlign: TextAlign.right,
),
)
),
Container(
width: SizeConfig.screenWidth,
margin: EdgeInsets.only(top: SizeConfig.heightMultiplier * 5),
child: StreamBuilder<bool>(
stream: login.submitCheck,
builder: (context, snapshot) => AppButton(
onPressed: snapshot.hasData ? () => login.login() : null,
text: Strings.signin
),
)
)
],
)
)
),
Expanded(
flex: 1,
child: Container(
alignment: Alignment.bottomCenter,
margin: EdgeInsets.only(bottom: SizeConfig.heightMultiplier * 2.5),
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
Strings.dontAccount,
style: AppTheme.styleSubTitleBlackSmall,
textAlign: TextAlign.right,
),
Container(
margin: EdgeInsets.only(left: SizeConfig.widthMultiplier * 1),
child: InkWell(
onTap: () => AppRoutes.push(context, RegistrationPage()),
child: Text(
Strings.registration,
style: AppTheme.styleSubTitlePurpel,
textAlign: TextAlign.right,
),
)
)
],
)
)
)
],
),
),
);
}
void _onWidgetDidBuild(Function callback) {
WidgetsBinding.instance.addPostFrameCallback((_) {
callback();
});
}
}

Answer 1

The problem is that you have created an instance of your bloc globally (which is not a good practice), and after the login process is done you have called login.dispose() which closes all of the streams in your LoginBloc, and you can't add new events to closed streams.
You'd better create an instance of your LoginBloc in your LoginPage initState method, and close it in the dispose method.
This way, whenever you navigate to login page, a new bloc is created and it would work as expected.
UPDATE:
A simple example:
class LoginPage extends StatefulWidget {
#override
_LoginPageState createState() => _LoginPageState();
}
class _LoginPageState extends State<LoginPage> {
LoginBloc _loginBloc;
#override
void initState() {
super.initState();
_loginBloc = LoginBloc();
}
#override
void dispose() {
_loginBloc.close();
super.dispose();
}
#override
Widget build(BuildContext context) {
return Container();
}
}