update focus login form

lib/presentation/screens/login/view/login_form.dart

 
 class LoginForm extends StatelessWidget {
   AuthenticationBloc _authenticationBloc;
+  FocusNode _usernameFocus = FocusNode();
+  FocusNode _passwordFocus = FocusNode();
 
   @override
   Widget build(BuildContext context) {
           mainAxisAlignment: MainAxisAlignment.spaceBetween,
           mainAxisSize: MainAxisSize.min,
           children: [
-            _UsernameInput(),
+            _UsernameInput(
+                usernameFocus: _usernameFocus, nextFocus: _passwordFocus),
             const Padding(padding: EdgeInsets.all(12)),
-            _PasswordInput(),
+            _PasswordInput(
+              passwordFocus: _passwordFocus,
+            ),
             const Padding(padding: EdgeInsets.all(16)),
             _LoginButton(),
             const Padding(padding: EdgeInsets.all(6)),
 }
 
 class _UsernameInput extends StatelessWidget {
+  final FocusNode usernameFocus;
+  final FocusNode nextFocus;
+  _UsernameInput({@required this.usernameFocus, @required this.nextFocus});
   @override
   Widget build(BuildContext context) {
     return BlocBuilder<LoginBloc, LoginState>(
                 color: COLOR_CONST.GRAY7),
             child: Center(
               child: TextFormField(
+                focusNode: usernameFocus,
+                textInputAction: TextInputAction.next,
                 onChanged: (username) => context
                     .bloc<LoginBloc>()
                     .add(LoginUsernameChanged(username)),
                       ? 'Vui lòng nhập tên đăng nhập'
                       : null;
                 },
+                onFieldSubmitted: (_) {
+                  usernameFocus.unfocus();
+                  FocusScope.of(context).requestFocus(nextFocus);
+                },
                 maxLines: 1,
                 keyboardType: TextInputType.text,
                 obscureText: false,
 }
 
 class _PasswordInput extends StatelessWidget {
+  final FocusNode passwordFocus;
+  _PasswordInput({this.passwordFocus});
   @override
   Widget build(BuildContext context) {
     return BlocBuilder<LoginBloc, LoginState>(
                 color: COLOR_CONST.GRAY7),
             child: Center(
               child: TextFormField(
+                focusNode: passwordFocus,
                 onChanged: (password) => context
                     .bloc<LoginBloc>()
                     .add(LoginPasswordChanged(password)),
                       ? 'Vui lòng nhập mật khẩu'
                       : null;
                 },
+                onFieldSubmitted: (_) {
+                  passwordFocus.unfocus();
+                  if (state.status.isValidated) {
+                    context.bloc<LoginBloc>().add(const LoginSubmitted());
+                  }
+                },
                 maxLines: 1,
                 keyboardType: TextInputType.text,
-                obscureText: false,
+                obscureText: true,
                 textAlign: TextAlign.left,
                 decoration: InputDecoration.collapsed(
                   hintText: 'Mật khẩu',