👨‍🏫0.6 Условия - if(){} - else if(){} - else{}

== - равно, <,>

import 'package:flutter/material.dart';

class Lesson19 extends StatefulWidget {
  const Lesson19({super.key});

  @override
  State<Lesson19> createState() => _Lesson19State();
}

class _Lesson19State extends State<Lesson19> {
  // ==,  >, <, >=, <=, is, ||, &&
  TextEditingController nameController = TextEditingController();

  String title = 'Welocme';

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      body: Padding(
        padding: const EdgeInsets.all(8.0),
        child: Column(
          spacing: 20,
          children: [
            Text(title, style: TextStyle(fontSize: 40)),
            TextFormField(
              controller: nameController,
              decoration: InputDecoration(border: OutlineInputBorder()),
            ),

            ElevatedButton(
              onPressed: () {
                setState(() {
                  if (nameController.text == 'Daniel') {
                    title = 'Привет Даниэль';
                  } else if (nameController.text == 'saikal') {
                    title = 'Hello Saikal';
                  } else if (nameController.text == 'Eldiar') {
                    title = 'Истина';
                  } else{
                    title = 'не смогли вас найти';
                  }
                });
              },
              child: Text('Apply'),
            ),
          ],
        ),
      ),
    );
  }
}

class Lesson19a extends StatefulWidget {
  const Lesson19a({super.key});

  @override
  State<Lesson19a> createState() => _Lesson19aState();
}

class _Lesson19aState extends State<Lesson19a> {
  TextEditingController ageController = TextEditingController();

  String title = 'Введите возраст';

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      body: Padding(
        padding: const EdgeInsets.all(8.0),
        child: Column(
          spacing: 20,
          children: [
            Text(title, style: TextStyle(fontSize: 40)),
            TextFormField(
              controller: ageController,
              decoration: InputDecoration(border: OutlineInputBorder()),
            ),

            ElevatedButton(
              onPressed: () {
                setState(() {
                  if (int.tryParse(ageController.text)! < 0) {
                    title = 'Ошибка возраст не может быть отрицаетльным';
                  } else if (ageController.text == 'saikal') {
                    title = 'Hello Saikal';
                  } else if (ageController.text == 'Eldiar') {
                    title = 'Истина';
                  } else{
                    title = 'не смогли вас найти';
                  }
                });
              },
              child: Text('Apply'),
            ),
          ],
        ),
      ),
    );
  }
}

class Lesson19b extends StatefulWidget {
  const Lesson19b({super.key});

  @override
  State<Lesson19b> createState() => _Lesson19bState();
}

class _Lesson19bState extends State<Lesson19b> {
  TextEditingController passwordController = TextEditingController();
  String title = '';
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      body: Padding(
        padding: const EdgeInsets.all(8.0),
        child: Column(
          children: [
            TextFormField(
              controller: passwordController,
              onChanged: (value){
                if(passwordController.text.isEmpty){
                  title ='Пустой';
                } else if (passwordController.text.length < 6){
                  title = 'Слишкым короткий';
                } else if (passwordController.text.length <=10){
                  title = 'слабый пароль';
                } else if (!passwordController.text.contains('&')){
                  title = 'добавьте &';
                } else{
                  title = 'пароль надежный';
                }

                setState(() {
                });
              },
              decoration: InputDecoration(
                suffixIcon: Text(title),
                hintText: 'Введите пароль'
              ),
            )
          ],
        ),
      )
    );
  }
}