import 'package:flutter/material.dart';

class MyApp extends StatefulWidget {
 @override
 _MyApp createState() => new _MyApp();
}

class _MyApp extends State<MyApp> {

 String _lastName;
 String _firstName;
 GlobalKey<FormState> _formKey = new GlobalKey<FormState>();

 void _showMessage(String name) {
  showDialog<Null>(
   context: context,
   child: new AlertDialog(
    content: new Text(name),
    actions: <Widget>[
     new FlatButton(
      onPressed: () {
       Navigator.pop(context);
      },
      child: new Text('確定')
     )
    ]
   )
  );
 }

 @override
 Widget build(BuildContext context) {
  return new Scaffold(
   appBar: new AppBar(
    title: new Text('表單輸入')
   ),
   // Form：用于將多個(gè)表單控件組合在一起的容器
   body: new Form(
    key: _formKey,
    child: new Column(
     children: <Widget> [
      // TextFieldd：包含輸入的表單控件，每個(gè)表單字段都應(yīng)該在FormField控件中
      new TextField(
       labelText: '姓氏',
       // onSaved：當(dāng)通過Form.save()保存表單時(shí)調(diào)用的方法
       onSaved: (InputValue value) {
        _lastName = value.text;
       }
      ),
      new TextField(
       labelText: '名字',
       onSaved: (InputValue value) {
        _firstName = value.text;
       }
      ),
      new Row(
       children: <Widget> [
        new RaisedButton(
         child: new Text('重置'),
         onPressed: () {
          // reset()：將此Form下的每個(gè)TextField重置為初始狀態(tài)
          _formKey.currentState.reset();
          _showMessage('姓名信息已經(jīng)重置');
         }
        ),
        new RaisedButton(
         child: new Text('提交'),
         onPressed: () {
          // save()：保存Form下的每個(gè)TextField
          _formKey.currentState.save();
          _showMessage('你的姓名是'+_lastName+_firstName);
         }
        )
       ]
      )
     ]
    )
   )
  );
 }
}

void main() {
 runApp(new MaterialApp(
  title: 'Flutter Demo',
  home: new MyApp()
 ));
}