flutter_form_validate.dart

import 'package:flutter/material.dart';
import 'package:validators/validators.dart' as thuvienkiemtra;
void main() {
  return runApp(MyApp());
}
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final _formKey = GlobalKey<FormState>();
  String email;
  String password;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("Example about form"),
        ),
        body: Center(
          child: Column(
            children: <Widget>[
              Text("Xin chao moi nguoi"),
              Form(
                key: _formKey,
                child: Column(children: <Widget>[
                  Padding(
                    padding: const EdgeInsets.all(8.0),
                    child: TextFormField(
                      decoration: InputDecoration(
                        hintText: "email",
                        border: InputBorder.none,
                        fillColor: Colors.grey[300],
                        filled: true,
                      ),
                      validator: (String value) {
                        if (!thuvienkiemtra.isEmail(value)) {
                          return "Email khong hop le";
                        }
                        return null;
                      },
                      onSaved: (String value) {
                        this.email = value;
                      },
                    ),
                  ),
                  Padding(
                    padding: const EdgeInsets.all(8.0),
                    child: TextFormField(
                      decoration: InputDecoration(
                        hintText: "password",
                        border: InputBorder.none,
                        fillColor: Colors.grey[300],
                        filled: true,
                      ),
                      obscureText: true,
                      validator: (String value) {
                        if (value.length < 8) {
                          return "Password khong hop le";
                        }
                        return null;
                      },
                      onSaved: (String value) {
                        this.password = value;
                      },
                    ),
                  ),
                  RaisedButton(
                    onPressed: () {
                      if (_formKey.currentState.validate()) {
                        _formKey.currentState.save();
                        print("Email la: " + this.email.toString());
                        print("Password la: " + this.password.toString());
                      }
                    },
                    child: Text("Kiem tra"),
                  )
                ],),
              )
            ],
          ),
        )
      );
  }
}