1 秒后打印每个列表值

Question

Anton

Asked:2020-05-21 03:18:25 +0000 UTC2020-05-21 03:18:25 +0000 UTC 2020-05-21 03:18:25 +0000 UTC

TextFormField 小部件中的 onSaved 事件处理程序不起作用

772

TextFormField小部件上的onSaved事件处理程序不起作用。

onSaved: (String value) {
 setState(() {
  _strNameUser = value;
 });
},

如果我理解正确，字符串值是出现在输入字段中的文本值。然后，我可以将它分配给任何变量。但什么也没有发生。一切都发生在控制器中。第一个代码没有控制器，它不起作用。第二个代码是一个替换onSaved的控制器。那里的代码有效。我不明白的原因是什么？

第一个代码没有控制器，它不起作用。

主要.dart

import 'package:flutter/material.dart';

import 'package:string_validator/string_validator.dart';

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

class MyApp extends StatelessWidget {
 @override
 Widget build(BuildContext context) {
  return MaterialApp(
   debugShowCheckedModeBanner: false,
   title: 'Name App',
   theme: ThemeData(
    primarySwatch: Colors.blue,
   ),
   home: Scaffold(
    appBar: AppBar(
     title: Text('Name Page'),
    ),
    body: MyHomePage(),
   ),
  );
 }
}
class MyHomePage extends StatefulWidget {
 @override
 _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
 //объявление переменных
 String _strNameUser;
 String _strEmail;
 String _str;
 bool _a, _b, _c;

 //вызывается один раз при инициализации виджета
 @override
 void initState() {
  super.initState();
  _strNameUser = '';
  _strEmail = '';
  _str = '';
 }

 @override
 void dispose() {
  super.dispose();

 }

 void _f1() {
  setState(() {
   _a = _strNameUser.isNotEmpty;
   _b = _strEmail.isNotEmpty;
   _c = isEmail(_strEmail);

   if(_a && _b && _c) {
    _str = 'user name : $_strNameUser\n email: $_strEmail';
   } else {
    _str = '';
   }
  });
 }

 @override
 Widget build(BuildContext context) {
  return Stack(
   children: <Widget>[
    Align(
     alignment: Alignment(0.0, -0.65),
     child: Column(
      mainAxisSize: MainAxisSize.min,
      crossAxisAlignment: CrossAxisAlignment.stretch,
      children: <Widget>[
       Container(
        height: 50.0,
        margin: const EdgeInsets.symmetric(horizontal: 16.0, vertical: 8.0),
        alignment: Alignment.center,
        child: TextFormField(
         onSaved: (String value) {
          setState(() {
           _strNameUser = value;
          });
         },
         cursorColor: Color(0xffF56323),
         style: TextStyle(
          color: Colors.deepPurple,
          fontSize: 22.0,
         ),
         decoration: InputDecoration(
          labelText: 'User Name',
          prefixIcon: (_a == null || _a) ? Icon(Icons.person, color: Color(0xffF56323)) : Icon(Icons.error, color: Colors.pink),
          border: OutlineInputBorder(
           borderRadius: BorderRadius.circular(10.0),
           borderSide: BorderSide(),
          ),
         ),
        ),
       ),
       Container(
        height: 50.0,
        margin: const EdgeInsets.symmetric(horizontal: 16.0, vertical: 8.0),
        alignment: Alignment.center,
        child: TextFormField(
         onSaved: (String value) {
          setState(() {
           _strEmail = value;
          });
         },
         keyboardType: TextInputType.emailAddress,
         cursorColor: Color(0xffF56323),
         style: TextStyle(
          color: Colors.deepPurple,
          fontSize: 22.0,
         ),
         decoration: InputDecoration(
          labelText: 'Email',
          prefixIcon: (_b == null || (_b && _c)) ? Icon(Icons.email, color: Color(0xffF56323)) : Icon(Icons.error, color: Colors.pink),
          border: OutlineInputBorder(
           borderRadius: BorderRadius.circular(10.0),
           borderSide: BorderSide()
          ),
         ),
        ),
       ),
       Container(
        height: 50.0,
        margin: const EdgeInsets.symmetric(horizontal: 16.0, vertical: 8.0),
        alignment: Alignment.center,
        child: Container(
         width: double.infinity,
         height: 50.0,
         child: FlatButton(
          onPressed: () {
           _f1();
          },
          color: Color(0xffF56323).withOpacity(0.9),
          splashColor: Colors.amberAccent,
          child: Text(
           'Ok',
           style: TextStyle(
            color: Colors.white,
            fontSize: 22.0,
           ),
          ),
          shape: RoundedRectangleBorder(
           borderRadius: BorderRadius.circular(10)
          ),
         ),
        ),
       ),
      ],
     ),
    ),
    Align(
     alignment: Alignment(0.0, 0.85),
     child: Text(
      _str,
      style: TextStyle(
       color: Colors.pink,
       fontSize: 26.0,
      ),
     ),
    ),
   ],
  );
 }
}

控制器的第二个代码有效。

主要.dart

import 'package:flutter/material.dart';

import 'package:string_validator/string_validator.dart';

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

class MyApp extends StatelessWidget {
 @override
 Widget build(BuildContext context) {
  return MaterialApp(
   debugShowCheckedModeBanner: false,
   title: 'Name App',
   theme: ThemeData(
    primarySwatch: Colors.blue,
   ),
   home: Scaffold(
    appBar: AppBar(
     title: Text('Name Page'),
    ),
    body: MyHomePage(),
   ),
  );
 }
}
class MyHomePage extends StatefulWidget {
 @override
 _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
 //объявление переменных
 TextEditingController _controllerUserName;
 TextEditingController _controllerEmail;
 String _strNameUser;
 String _strEmail;
 String _str;
 bool _a, _b, _c;

 //вызывается один раз при инициализации виджета
 @override
 void initState() {
  super.initState();
  _controllerUserName = TextEditingController();
  _controllerEmail = TextEditingController();
  _strNameUser = '';
  _strEmail = '';
  _str = '';
 }

 @override
 void dispose() {
  super.dispose();

 }

 void _f1() {
  setState(() {
   _strNameUser = _controllerUserName.text;
   _strEmail = _controllerEmail.text;

   _a = _strNameUser.isNotEmpty;
   _b = _strEmail.isNotEmpty;
   _c = isEmail(_strEmail);

   if(_a && _b && _c) {
    _str = 'user name : $_strNameUser\n email: $_strEmail';
   } else {
    _str = '';
   }
  });
 }

 @override
 Widget build(BuildContext context) {
  return Stack(
   children: <Widget>[
    Align(
     alignment: Alignment(0.0, -0.65),
      child: Column(
       mainAxisSize: MainAxisSize.min,
       crossAxisAlignment: CrossAxisAlignment.stretch,
       children: <Widget>[
        Container(
         height: 50.0,
         margin: const EdgeInsets.symmetric(horizontal: 16.0, vertical: 8.0),
         alignment: Alignment.center,
         child: TextFormField(
          controller: _controllerUserName,
          cursorColor: Color(0xffF56323),
          style: TextStyle(
           color: Colors.deepPurple,
           fontSize: 22.0,
          ),
          decoration: InputDecoration(
           labelText: 'User Name',
           prefixIcon: (_a == null || _a) ? Icon(Icons.person, color: Color(0xffF56323)) : Icon(Icons.error, color: Colors.pink),
           border: OutlineInputBorder(
            borderRadius: BorderRadius.circular(10.0),
            borderSide: BorderSide(),
           ),
          ),
         ),
        ),
        Container(
         height: 50.0,
         margin: const EdgeInsets.symmetric(horizontal: 16.0, vertical: 8.0),
         alignment: Alignment.center,
         child: TextFormField(
          controller: _controllerEmail,
          keyboardType: TextInputType.emailAddress,
          cursorColor: Color(0xffF56323),
          style: TextStyle(
           color: Colors.deepPurple,
           fontSize: 22.0,
          ),
          decoration: InputDecoration(
           labelText: 'Email',
           prefixIcon: (_b == null || (_b && _c)) ? Icon(Icons.email, color: Color(0xffF56323)) : Icon(Icons.error, color: Colors.pink),
           border: OutlineInputBorder(
            borderRadius: BorderRadius.circular(10.0),
            borderSide: BorderSide()
           ),
          ),
         ),
        ),
        Container(
         height: 50.0,
         margin: const EdgeInsets.symmetric(horizontal: 16.0, vertical: 8.0),
         alignment: Alignment.center,
         child: Container(
          width: double.infinity,
          height: 50.0,
          child: FlatButton(
           onPressed: () {
            _f1();
           },
           color: Color(0xffF56323).withOpacity(0.9),
           splashColor: Colors.amberAccent,
           child: Text(
            'Ok',
            style: TextStyle(
             color: Colors.white,
             fontSize: 22.0,
            ),
           ),
           shape: RoundedRectangleBorder(
            borderRadius: BorderRadius.circular(10)
           ),
          ),
         ),
        ),
       ],
      ),
    ),
    Align(
     alignment: Alignment(0.0, 0.85),
     child: Text(
      _str,
      style: TextStyle(
       color: Colors.pink,
       fontSize: 26.0,
      ),
     ),
    ),
   ],
  );
 }
}

1 个回答

Voted

MiT · Answer 1 · 2020-05-22T01:31:39Z

Best Answer

MiT

2020-05-22T01:31:39Z2020-05-22T01:31:39Z

不幸的是，您误解了 onSaved 方法，它是在保存时调用附加代码所必需的，而 value 是用于发送到附加代码。

https://api.flutter.dev/flutter/material/TextFormField-class.html

onSaved: (String value) {
  // This optional block of code can be used to run
  // code when the user saves the form.
},

您需要调用表单保存：

Form.of(primaryFocus.context).save();

并且以牺牲控制器为代价，您正确理解，顾名思义，它控制/控制某些东西（在本例中TextFormField）

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