इनपुट सत्यापन तकनीकें

import 'package:flutter/material.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Validation Demo',
      home: Scaffold(
        appBar: AppBar(title: const Text('Basic Validation')),
        body: const MyCustomForm(),
      ),
    );
  }
}

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

  @override
  State<MyCustomForm> createState() => _MyCustomFormState();
}

class _MyCustomFormState extends State<MyCustomForm> {
  final _formKey = GlobalKey<FormState>();

  @override
  Widget build(BuildContext context) {
    return Form(
      key: _formKey,
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          Padding(
            padding: const EdgeInsets.all(8.0),
            child: TextFormField(
              decoration: const InputDecoration(
                hintText: 'Enter your name',
                labelText: 'Name',
              ),
              validator: (value) {
                if (value == null || value.isEmpty) {
                  return 'Please enter some text';
                }
                return null;
              },
            ),
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 16.0),
            child: ElevatedButton(
              onPressed: () {
                if (_formKey.currentState!.validate()) {
                  ScaffoldMessenger.of(context).showSnackBar(
                    const SnackBar(content: Text('Processing Data')),
                  );
                }
              },
              child: const Text('Submit'),
            ),
          ),
        ],
      ),
    );
  }
}

import 'package:flutter/material.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Validation Demo',
      home: Scaffold(
        appBar: AppBar(title: const Text('Custom Validation')),
        body: const MyCustomForm(),
      ),
    );
  }
}

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

  @override
  State<MyCustomForm> createState() => _MyCustomFormState();
}

class _MyCustomFormState extends State<MyCustomForm> {
  final _formKey = GlobalKey<FormState>();

  @override
  Widget build(BuildContext context) {
    return Form(
      key: _formKey,
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          Padding(
            padding: const EdgeInsets.all(8.0),
            child: TextFormField(
              obscureText: true,
              decoration: const InputDecoration(
                hintText: 'Enter a password',
                labelText: 'Password',
              ),
              validator: (value) {
                if (value == null || value.isEmpty) {
                  return 'Please enter a password';
                }
                if (value.length < 6) {
                  return 'Password must be at least 6 chars';
                }
                return null;
              },
            ),
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 16.0),
            child: ElevatedButton(
              onPressed: () {
                if (_formKey.currentState!.validate()) {
                  ScaffoldMessenger.of(context).showSnackBar(
                    const SnackBar(content: Text('Password is valid!')),
                  );
                }
              },
              child: const Text('Submit'),
            ),
          ),
        ],
      ),
    );
  }
}

import 'package:flutter/material.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Regex Validation Demo',
      home: Scaffold(
        appBar: AppBar(title: const Text('Email Validation')),
        body: const MyCustomForm(),
      ),
    );
  }
}

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

  @override
  State<MyCustomForm> createState() => _MyCustomFormState();
}

class _MyCustomFormState extends State<MyCustomForm> {
  final _formKey = GlobalKey<FormState>();
  final RegExp emailRegex = RegExp(
      r"^[a-zA-Z0-9.]+@[a-zA-Z0-9]+\.[a-zA-Z]+"
  );

  @override
  Widget build(BuildContext context) {
    return Form(
      key: _formKey,
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          Padding(
            padding: const EdgeInsets.all(8.0),
            child: TextFormField(
              keyboardType: TextInputType.emailAddress,
              decoration: const InputDecoration(
                hintText: 'Enter your email',
                labelText: 'Email',
              ),
              validator: (value) {
                if (value == null || value.isEmpty) {
                  return 'Please enter an email';
                }
                if (!emailRegex.hasMatch(value)) {
                  return 'Please enter a valid email format';
                }
                return null;
              },
            ),
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 16.0),
            child: ElevatedButton(
              onPressed: () {
                if (_formKey.currentState!.validate()) {
                  ScaffoldMessenger.of(context).showSnackBar(
                    const SnackBar(content: Text('Email is valid!')),
                  );
                }
              },
              child: const Text('Submit'),
            ),
          ),
        ],
      ),
    );
  }
}

import 'package:flutter/material.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Auto Validate Demo',
      home: Scaffold(
        appBar: AppBar(title: const Text('Auto-Validation')),
        body: const MyCustomForm(),
      ),
    );
  }
}

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

  @override
  State<MyCustomForm> createState() => _MyCustomFormState();
}

class _MyCustomFormState extends State<MyCustomForm> {
  final _formKey = GlobalKey<FormState>();

  @override
  Widget build(BuildContext context) {
    return Form(
      key: _formKey,
      // Auto-validate as user types
      autovalidateMode: AutovalidateMode.always,
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          Padding(
            padding: const EdgeInsets.all(8.0),
            child: TextFormField(
              decoration: const InputDecoration(
                hintText: 'Enter text (min 3 chars)',
                labelText: 'Input',
              ),
              validator: (value) {
                if (value == null || value.length < 3) {
                  return 'Must be at least 3 characters';
                }
                return null;
              },
            ),
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 16.0),
            child: ElevatedButton(
              onPressed: () {
                // Manual validation still works
                if (_formKey.currentState!.validate()) {
                  ScaffoldMessenger.of(context).showSnackBar(
                    const SnackBar(content: Text('Input is valid!')),
                  );
                }
              },
              child: const Text('Submit'),
            ),
          ),
        ],
      ),
    );
  }
}