[FLUTTER] TextFormField 클래스 : validator 속성을 사용해 입력 값 검증하기

■ TextFormField 클래스의 validator 속성을 사용해 입력 값을 검증하는 방법을 보여준다.

▶ main.dart


import 'package:flutter/material.dart';

void main() => runApp(TestApplication());

class TestApplication extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Test Application',
      home: Scaffold(
        appBar: AppBar(
          title: Text('Test Application'),
        ),
        body: MainPage(),
      ),
    );
  }
}

class MainPage extends StatefulWidget {
  @override
  _MainPageState createState() => _MainPageState();
}

class _MainPageState extends State<MainPage> {
  final GlobalKey<FormState> _formKey = GlobalKey<FormState>();

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.all(16.0),
      child: Form(
        key: _formKey,
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: <Widget>[
            TextFormField(
              validator: (value) {
                if (value.isEmpty) {
                  return '주소를 입력해 주시기 바랍니다.';
                }
                return null;
              },
            ),
            Padding(
              padding: const EdgeInsets.symmetric(vertical: 16.0),
              child: RaisedButton(
                child: Text('검증'),
                onPressed: () {
                  if (_formKey.currentState.validate()) {
                    Scaffold.of(context).showSnackBar(SnackBar(content: Text('정상적으로 입력되었습니다.')));
                  }
                },
              ),
            ),
          ],
        ),
      ),
    );
  }
}

import 'package:flutter/material.dart';

void main() => runApp(TestApplication());

class TestApplication extends StatelessWidget {

@override

Widget build(BuildContext context) {

return MaterialApp(

title: 'Test Application',

home: Scaffold(

appBar: AppBar(

title: Text('Test Application'),

body: MainPage(),

);

}

class MainPage extends StatefulWidget {

@override

_MainPageState createState() => _MainPageState();

}

class _MainPageState extends State<MainPage> {

final GlobalKey<FormState> _formKey = GlobalKey<FormState>();

@override

Widget build(BuildContext context) {

return Padding(

padding: const EdgeInsets.all(16.0),

child: Form(

key: _formKey,

child: Column(

crossAxisAlignment: CrossAxisAlignment.start,

children: <Widget>[

TextFormField(

validator: (value) {

if (value.isEmpty) {

return '주소를 입력해 주시기 바랍니다.';

}

return null;

Padding(

padding: const EdgeInsets.symmetric(vertical: 16.0),

child: RaisedButton(

child: Text('검증'),

onPressed: () {

if (_formKey.currentState.validate()) {

Scaffold.of(context).showSnackBar(SnackBar(content: Text('정상적으로 입력되었습니다.')));

}

);

}