main.dart

import 'package:flutter/material.dart';
import 'package:flutter_application_1/myhomepages.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(

        primarySwatch: Colors.blue,
      ),
      home: const MyHomePages(),
    );
  }
}

myhomepages.dart

import 'package:flutter/material.dart';
import 'package:flutter/src/widgets/container.dart';
import 'package:flutter/src/widgets/framework.dart';

class MyHomePages extends StatefulWidget {
  const MyHomePages({super.key});

  @override
  State<MyHomePages> createState() => _MyHomePagesState();
}

class _MyHomePagesState extends State<MyHomePages> {
   final _formkey = GlobalKey<FormState>();
   var name="";
   var email="";
   var password="";
   final nameController = TextEditingController();
   final emailController = TextEditingController();
   final passwordController = TextEditingController();
  @override
  Widget build(BuildContext context) {
   return MaterialApp(  
      home: Scaffold(  
        appBar: AppBar(  
          title: Text("Flutter Container Example"),  
        ),  
        body: Form(

      key: _formkey,
      child: Padding(
      padding:const EdgeInsets.symmetric(vertical:40,horizontal:30)
      ,child: ListView(
        children: [
          TextFormField(
            decoration:const InputDecoration(labelText:'Name:',
            labelStyle: TextStyle(fontSize:40),
            errorStyle: TextStyle(color:Colors.redAccent,fontSize:20 )),
            controller: nameController,
            validator: (value){
                //  print("validation me aarha hai");
              if(value!.isEmpty){
                //  print("validation IF me aarha hai");
 
                print(value);
                return 'please Enter Name';
              }
            },
            ),
          TextFormField(
            decoration:const InputDecoration(labelText:'Email:',
            labelStyle: TextStyle(fontSize:40)),
            controller: emailController,
            validator: (value){
              if(value!.isEmpty){
                return 'please Enter Email';
              }

              else if(!value.contains('@'))
              {
                return 'please Enter Valid Email';
              }
            },
            ),
            TextFormField(
              obscureText: true,
            decoration:const InputDecoration(labelText:'password:',
            labelStyle: TextStyle(fontSize:40)),
            controller: passwordController,
            validator: (value){
              if(value!.isEmpty){
                return 'please Enter password';
              }
            },
            ),
            ElevatedButton(
              onPressed: (){
              if(_formkey.currentState!.validate()){
                setState(() {
                  name=nameController.text;
                  email=emailController.text;
                  password=passwordController.text;
                });
              }
            },
            child: 
            Text('submit')),
            Text('Name: $name'),
            Text('Email: $email'),
            Text('Password: $password'),
            ],

        ),
      )
      ),
      ),  
    );  
  }  
}

class _formkey {
  static var currentState;
}  

OutPut