Flutter: Observable.combineLatest2 is not streaming when page is loaded through navigation - dart

Question

I am creating a flutter app with blocs.
I followed the code available in Flutter login with blocs
It works as expected,
if my app has no routes defined
class App extends StatelessWidget {
Widget build(BuildContext context) {
return Provider(
child: MaterialApp(
title: 'Log Me In!',
home: Scaffold(
body: LoginScreen(),
),
),
);
}
}
but when I change my app to use routes
class App extends StatelessWidget {
Widget build(BuildContext context) {
return MaterialApp(
title: 'Log Me In!',
routes: {
'/':(context) => Provider(
child: Scaffold(
body: LoginScreen(),
),
)
},
);
}
}
bloc code
class Bloc extends Object with Validators {
final _email = BehaviorSubject<String>();
final _password = BehaviorSubject<String>();
// retrieve data from stream
Stream<String> get email => _email.stream.transform(validateEmail);
Stream<String> get password => _password.stream.transform(validatePassword);
Stream<bool> get submitValid => Observable.combineLatest2(email, password, (e, p) => true);
// add data to stream
Function(String) get changeEmail => _email.sink.add;
Function(String) get changePassword => _password.sink.add;
submit() {
final validEmail = _email.value;
final validPassword = _password.value;
print('$validEmail and $validPassword');
}
dispose() {
_email.close();
_password.close();
}
}
Observable.combileLatest2 is not streaming the data (but it streams error though).
Using Rxdart version 0.19.0 and
Flutter 1.0.0 • channel beta •https://github.com/flutter/flutter.git
Framework • revision 5391447fae (6 days ago) • 2018-11-29 19:41:26-0800
Engine • revision 7375a0f414Tools • Dart 2.1.0 (build 2.1.0-dev.9.4 f9ebf21297)
Am I doing something wrong here?
thanks in advance

Answer 1

After lot of trial, I found that when I use routes for the navigation, flutter will build the page multiple times and thats the expected behavior refer here for detailed answer
So when it builds the page multiple times, it was creating multiple Observables on the bloc as it was creating new instance of Bloc every time it creates the Page route.
So when I modify the code
class App extends StatelessWidget {
final login = Provider(
child: Scaffold(
body: LoginScreen(),
),
);
Widget build(BuildContext context) {
return MaterialApp(
title: 'Log Me In!',
routes: {
'/':(context) => login,
},
);
}
}
it worked perfectly.
The other way is to achieve is to create a stateful widget and do the initialization in the init method.