i making authentication login form ,i want to connect submitAuthForm Funtion to the AuthForm that's why i pass reference in the AuthForm,i am beginer please help me to solve this problem( The argument type 'void Function(String, String, String, bool)' can't be assigned to the parameter type 'Void Function(String, String, String, bool)''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''Thanks

class AuthScreen extends StatefulWidget {
  

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

class _AuthScreenState extends State<AuthScreen> {
  void _submitAuthForm(
      String email, 
      String password, 
      String username, 
      bool isLogin) {

      }
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        backgroundColor: Theme.of(context).primaryColor,
        body: Authform(_submitAuthForm,)/*( The argument type 'void Function(String, String, String, bool)' can't be assigned to the parameter type 'Void Function(String, String, String, bool)'.*/)
        );
  }
}

class Authform extends StatefulWidget {
  
  Authform(this.submitFN);

  final Void Function(
      String email, String password, String username, bool isLogin) submitFN;

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

class _AuthformState extends State<Authform> {
  final _formKey = GlobalKey<FormState>();

  var _isLogin = true;
  var _userEmail;
  var _userName;
  var _userPassword;

  void _trySubmit() {
    final isValid = _formKey.currentState!.validate();
    FocusScope.of(context).unfocus();
    if (isValid) {
      _formKey.currentState!.save();
      widget.submitFN(_userEmail,_userPassword,_userName,_isLogin);
    }
  }

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Card(
        margin: EdgeInsets.all(20),
        child: SingleChildScrollView(
            child: Padding(
          padding: EdgeInsets.all(16),
          child: Form(
              key: _formKey,
              child: Column(
                mainAxisSize: MainAxisSize.min,
                children: [
                  TextFormField(
                    key: ValueKey('email'),
                    validator: (value) {
                      if (value!.isEmpty || !value.contains('@')) {
                        return 'please enter valid email address';
                      }
                      return null;
                    },
                    keyboardType: TextInputType.emailAddress,
                    decoration: InputDecoration(
                        icon: Icon(
                          Icons.mail,
                          color: Colors.orange,
                        ),
                        labelText: 'Email Addess'),
                    onSaved: (value) {
                      _userEmail = value;
                    },
                  ),
                  if (!_isLogin)
                    TextFormField(
                      key: ValueKey('username'),
                      validator: (value) {
                        if (value!.isEmpty || value.length < 4) {
                          return 'Username is short enter atleast 4 characters ';
                        }
                      },
                      decoration: InputDecoration(
                          icon: Icon(
                            Icons.person,
                            color: Colors.orange,
                          ),
                          labelText: 'Username'),
                      onSaved: (value) {
                        _userName = value;
                      },
                    ),
                  TextFormField(
                    key: ValueKey('password'),
                    validator: (value) {
                      if (value!.isEmpty || value.length < 7) {
                        return 'Password must be atleast 7 characters long';
                      }
                      return null;
                    },
                    decoration: InputDecoration(
                      icon: Icon(
                        Icons.lock,
                        color: Colors.orange,
                      ),
                      labelText: 'password',
                    ),
                    obscureText: true,
                    onSaved: (value) {
                      _userPassword = value;
                    },
                  ),
                  SizedBox(
                    height: 12,
                  ),
                  ElevatedButton(
                    onPressed: _trySubmit,
                    child: Text(_isLogin ? 'Login' : 'Signup'),
                    style: ElevatedButton.styleFrom(onPrimary: Colors.white),
                  ),
                  TextButton(
                      onPressed: () {
                        setState(() {
                          _isLogin = !_isLogin;
                        });
                      },
                      child: Text(_isLogin
                          ? 'Create new account'
                          : 'I already have a acoount'))
                ],
              )),
        )),
      ),
    );
  }
}

CodePudding user response：

When declaring a function or variable you have follow proper declaring method to avoid unusual issues. You have declare your function using Void the V is in capital case there but it must be in small case like void. Juts change this like :

final Void Function(

to

final void Function(

CodePudding user response：

import 'package:flutter/material.dart';

void main(List<String> args) {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      theme: ThemeData(),
      home: AuthScreen(),
    );
  }
}

class AuthScreen extends StatefulWidget {
  @override
  _AuthScreenState createState() => _AuthScreenState();
}

class _AuthScreenState extends State<AuthScreen> {
  void _submitAuthForm(
      String email, String password, String username, bool isLogin) {}
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        backgroundColor: Theme.of(context).primaryColor,
        body: Authform(
          _submitAuthForm,
        ));
  }
}

class Authform extends StatefulWidget {
  Authform(this.submitFN);

  final void Function(
      String email, String password, String username, bool isLogin) submitFN;

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

class _AuthformState extends State<Authform> {
  final _formKey = GlobalKey<FormState>();

  var _isLogin = true;
  var _userEmail;
  var _userName;
  var _userPassword;

  void _trySubmit() {
    final isValid = _formKey.currentState!.validate();
    FocusScope.of(context).unfocus();
    if (isValid) {
      _formKey.currentState!.save();
      widget.submitFN(_userEmail, _userPassword, _userName, _isLogin);
    }
  }

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Card(
        margin: EdgeInsets.all(20),
        child: SingleChildScrollView(
            child: Padding(
          padding: EdgeInsets.all(16),
          child: Form(
              key: _formKey,
              child: Column(
                mainAxisSize: MainAxisSize.min,
                children: [
                  TextFormField(
                    key: ValueKey('email'),
                    validator: (value) {
                      if (value!.isEmpty || !value.contains('@')) {
                        return 'please enter valid email address';
                      }
                      return null;
                    },
                    keyboardType: TextInputType.emailAddress,
                    decoration: InputDecoration(
                        icon: Icon(
                          Icons.mail,
                          color: Colors.orange,
                        ),
                        labelText: 'Email Addess'),
                    onSaved: (value) {
                      _userEmail = value;
                    },
                  ),
                  if (!_isLogin)
                    TextFormField(
                      key: ValueKey('username'),
                      validator: (value) {
                        if (value!.isEmpty || value.length < 4) {
                          return 'Username is short enter atleast 4 characters ';
                        }
                      },
                      decoration: InputDecoration(
                          icon: Icon(
                            Icons.person,
                            color: Colors.orange,
                          ),
                          labelText: 'Username'),
                      onSaved: (value) {
                        _userName `enter code here`= value;
                      },
                    ),
                  TextFormField(
                    key: ValueKey('password'),
                    validator: (value) {
                      if (value!.isEmpty || value.length < 7) {
                        return 'Password must be atleast 7 characters long';
                      }
                      return null;
                    },
                    decoration: InputDecoration(
                      icon: Icon(
                        Icons.lock,
                        color: Colors.orange,
                      ),
                      labelText: 'password',
                    ),
                    obscureText: true,
                    onSaved: (value) {
                      _userPassword = value;
                    },
                  ),
                  SizedBox(
                    height: 12,
                  ),
                  ElevatedButton(
                    onPressed: _trySubmit,
                    child: Text(_isLogin ? 'Login' : 'Signup'),
                    style: ElevatedButton.styleFrom(onPrimary: Colors.white),
                  ),
                  TextButton(
                      onPressed: () {
                        setState(() {
                          _isLogin = !_isLogin;
                        });
                      },
                      child: Text(_isLogin
                          ? 'Create new account'
                          : 'I already have a acoount'))
                ],
              )),
        )),
      ),
    );
  }
}