Adding focus

Register.dart

String _validateEmail(String email) {
  // 1
  RegExp regex = RegExp(r'\w+@\w+\.\w+');
  // Add the following line to set focus to the email field
  if (email.isEmpty || !regex.hasMatch(email)) _emailFocusNode.requestFocus();
  // 2
  if (email.isEmpty)
    return 'We need an email address';
  else if (!regex.hasMatch(email))
    // 3
    return "That doesn't look like an email address";
  else
    // 4
    return null;
}