How to implement validation with keyboard done button Flutter, observable, streamBuilder - flutter

Question

I'm building an app with Flutter and Bloc like architecture. I'm trying to call submit func with not only login button but also keyboard done button with password; only when email and password are valid.
I could implement login button version with combineLatest, but I'm not sure keyboard version. I need to validate both email and password when keyboard done button pressed before calling submit. I could nest streamBuilder, but I feel it is not good practice.
Is there any way to get the latest value from combineLatest? BehaviorSubject<bool>().value Or any possible advice to implement this.
sample code:
final _emailController = BehaviorSubject<String>();
final _passwordController = BehaviorSubject<String>();
// Add data to stream
Stream<String> get email => _emailController.stream.transform(validateEmail);
Stream<String> get password =>
_passwordController.stream.transform(validatePassword);
Stream<bool> get submitValid =>
Observable.combineLatest2(email, password, (e, p) => true);
// change data
Function(String) get changeEmail => _emailController.sink.add;
Function(String) get changePassword => _passwordController.sink.add;
submit() {
final validEmail = _emailController.value;
final validPassword = _passwordController.value;
print('Email is $validEmail, and password is $validPassword');
}
import 'package:flutter/material.dart';
import '../blocs/bloc.dart';
import '../blocs/provider.dart';
class LoginScreen extends StatelessWidget {
#override
Widget build(BuildContext context) {
final bloc = Provider.of(context);
return Container(
margin: EdgeInsets.all(20.0),
child: Column(
children: <Widget>[
emailField(bloc),
passwordField(bloc),
Container(
margin: EdgeInsets.only(top: 25.0),
),
submitButton(bloc),
],
),
);
}
Widget emailField(Bloc bloc) {
return StreamBuilder(
stream: bloc.email,
builder: (context, snapshot) {
return TextField(
onChanged: bloc.changeEmail,
keyboardType: TextInputType.emailAddress,
decoration: InputDecoration(
hintText: 'ypu#example.com',
labelText: 'Email Address',
errorText: snapshot.error,
),
);
},
);
}
Widget passwordField(Bloc bloc) {
return StreamBuilder(
stream: bloc.password,
builder: (context, snapshot) {
return TextField(
obscureText: true,
onChanged: bloc.changePassword,
decoration: InputDecoration(
hintText: 'Password',
labelText: 'Password',
errorText: snapshot.error,
),
textInputAction: TextInputAction.done,
onSubmitted: () {}, // <- here
);
});
}
Widget submitButton(Bloc bloc) {
return StreamBuilder(
stream: bloc.submitValid,
builder: (context, snapshot) {
return RaisedButton(
child: Text('Login'),
color: Colors.blue,
onPressed: snapshot.hasData ? bloc.submit : null,
);
},
);
}
}

Answer 1

You can wrap Your Password streamBuilder with another streamBilder and onSubmitted call submit method.
Widget passwordField(Bloc bloc) {
return StreamBuilder(
stream: bloc.submitValid,
builder: (context, snap) {
return StreamBuilder(
stream: bloc.password,
builder: (context, snapshot) {
return TextField(
obscureText: true,
onChanged: bloc.changePassword,
decoration: InputDecoration(
hintText: 'Password',
labelText: 'Password',
errorText: snapshot.error,
),
textInputAction: TextInputAction.done,
onSubmitted: snap.hasData ? bloc.submit : null,
);
});
});
}