FocusScope bug

main.dart

// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'dart:async';

import 'package:flutter/material.dart';

void main() => runApp(MyApp());


class Bloc {
  final StreamController<String> _name = StreamController.broadcast();
  final StreamController<String> _firstName = StreamController.broadcast();
  final StreamController<String> _secondaryName = StreamController.broadcast();
  
  Stream<String> get name => _name.stream;
  Stream<String> get firstName => _firstName.stream;
  Stream<String> get secondaryName => _secondaryName.stream;
  Sink<String> get updateName => _name.sink;
  Sink<String> get updateFirstName => _firstName.sink;
  Sink<String> get updateSecondaryName => _secondaryName.sink;
  
}



class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final _bloc = Bloc();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: FocusTraversalGroup(
        policy: OrderedTraversalPolicy(),
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
                  _CustomTextField(
                      order: 1,
                      stream: _bloc.firstName,
                      sink: _bloc.updateFirstName,
                      label: 'firstNameField',
                    ),
                    _CustomTextField(
                      order: 2,
                      stream: _bloc.name,
                      sink: _bloc.updateName,
                      label: 'nameField',
                    ),
                    _CustomTextField(
                      order: 3,
                      stream: _bloc.secondaryName,
                      sink: _bloc.updateSecondaryName,
                      label: 'secondaryLastNameField',
                    ),
          ],
        ),
      ),
    );
  }
}
class _CustomTextField extends StatelessWidget {
  final Stream<String> stream;
  final Sink<String> sink;
  final String label;
  final TextInputAction textInputAction;
  final double order;

  _CustomTextField({this.order, this.label, this.textInputAction, this.stream, this.sink, Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return FocusTraversalOrder(
      order: NumericFocusOrder(order),
      child: StreamBuilder(
        stream: stream,
        builder: (_, snapshot) {
          final text = snapshot;
          return TextField(
            decoration: InputDecoration(
              labelText: label,
              // ignore: avoid_as
              errorText: (text.error)?.toString(),
            ),
            textInputAction: textInputAction ?? TextInputAction.next,
            onSubmitted: (_) {
              print('submitted order $order');
              if (textInputAction == TextInputAction.done) {
                FocusScope.of(context).unfocus();
              } else {
                FocusScope.of(context).nextFocus();
              }
            },
          );
        },
      ),
    );
  }
}