你好，我在尝试运行代码时遇到了这个错误
以下是完整的错误：
======== Exception caught by widgets library =======================================================
The following NoSuchMethodError was thrown building LoginScreen(dirty):
Closure call with mismatched arguments: function 'LoginScreen.build.<anonymous closure>'
Receiver: Closure: (String) => String?
Tried calling: LoginScreen.build.<anonymous closure>()
Found: LoginScreen.build.<anonymous closure>(String) => String?
The relevant error-causing widget was:
LoginScreen LoginScreen:file:///C:/Users/diaaa/AndroidStudioProjects/udemy_flutter/lib/main.dart:24:13
When the exception was thrown, this was the stack:
#0 Object.noSuchMethod (dart:core-patch/object_patch.dart:63:5)
#1 _objectNoSuchMethod (dart:core-patch/object_patch.dart:106:9)
#2 defaultFormFeild (package:udemy_flutter/shared/components/components.dart:41:26)
#3 LoginScreen.build (package:udemy_flutter/modules/login/login_screen.dart:31:19)
#4 StatelessElement.build (package:flutter/src/widgets/framework.dart:4739:28)
#5 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4665:15)
#6 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#7 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:4643:5)
#8 ComponentElement.mount (package:flutter/src/widgets/framework.dart:4638:5)
... Normal element mounting (169 frames)
#177 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3673:14)
#178 MultiChildRenderObjectElement.inflateWidget (package:flutter/src/widgets/framework.dart:6333:36)
#179 MultiChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:6344:32)
... Normal element mounting (362 frames)
#541 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3673:14)
#542 Element.updateChild (package:flutter/src/widgets/framework.dart:3425:18)
#543 RenderObjectToWidgetElement._rebuild (package:flutter/src/widgets/binding.dart:1198:16)
#544 RenderObjectToWidgetElement.mount (package:flutter/src/widgets/binding.dart:1167:5)
#545 RenderObjectToWidgetAdapter.attachToRenderTree.<anonymous closure> (package:flutter/src/widgets/binding.dart:1112:18)
#546 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2573:19)
#547 RenderObjectToWidgetAdapter.attachToRenderTree (package:flutter/src/widgets/binding.dart:1111:13)
#548 WidgetsBinding.attachRootWidget (package:flutter/src/widgets/binding.dart:944:7)
#549 WidgetsBinding.scheduleAttachRootWidget.<anonymous closure> (package:flutter/src/widgets/binding.dart:924:7)
(elided 11 frames from class _RawReceivePortImpl, class _Timer, dart:async, and dart:async-patch)
====================================================================================================
======== Exception caught by widgets library =======================================================
The following NoSuchMethodError was thrown building LoginScreen(dirty):
Closure call with mismatched arguments: function 'LoginScreen.build.<anonymous closure>'
Receiver: Closure: (String) => String?
Tried calling: LoginScreen.build.<anonymous closure>()
Found: LoginScreen.build.<anonymous closure>(String) => String?
The relevant error-causing widget was:
LoginScreen LoginScreen:file:///C:/Users/diaaa/AndroidStudioProjects/udemy_flutter/lib/main.dart:24:13
When the exception was thrown, this was the stack:
#0 Object.noSuchMethod (dart:core-patch/object_patch.dart:63:5)
#1 _objectNoSuchMethod (dart:core-patch/object_patch.dart:106:9)
#2 defaultFormFeild (package:udemy_flutter/shared/components/components.dart:41:26)
#3 LoginScreen.build (package:udemy_flutter/modules/login/login_screen.dart:31:19)
#4 StatelessElement.build (package:flutter/src/widgets/framework.dart:4739:28)
#5 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4665:15)
#6 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#7 StatelessElement.update (package:flutter/src/widgets/framework.dart:4746:5)
#8 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#9 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6202:14)
#10 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#11 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4690:16)
#12 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#13 StatelessElement.update (package:flutter/src/widgets/framework.dart:4746:5)
#14 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#15 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6202:14)
#16 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#17 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6202:14)
#18 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#19 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4690:16)
#20 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4840:11)
#21 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#22 StatefulElement.update (package:flutter/src/widgets/framework.dart:4872:5)
#23 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#24 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6202:14)
#25 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#26 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6202:14)
#27 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#28 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4690:16)
#29 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4840:11)
#30 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#31 StatefulElement.update (package:flutter/src/widgets/framework.dart:4872:5)
#32 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#33 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4690:16)
#34 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#35 StatelessElement.update (package:flutter/src/widgets/framework.dart:4746:5)
#36 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#37 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4690:16)
#38 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4840:11)
#39 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#40 StatefulElement.update (package:flutter/src/widgets/framework.dart:4872:5)
#41 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#42 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6202:14)
#43 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#44 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6202:14)
#45 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#46 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4690:16)
#47 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#48 ProxyElement.update (package:flutter/src/widgets/framework.dart:5020:5)
#49 _InheritedNotifierElement.update (package:flutter/src/widgets/inherited_notifier.dart:181:11)
#50 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#51 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6202:14)
#52 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#53 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4690:16)
#54 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4840:11)
#55 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#56 StatefulElement.update (package:flutter/src/widgets/framework.dart:4872:5)
#57 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#58 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4690:16)
#59 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#60 ProxyElement.update (package:flutter/src/widgets/framework.dart:5020:5)
#61 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#62 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4690:16)
#63 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#64 ProxyElement.update (package:flutter/src/widgets/framework.dart:5020:5)
#65 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#66 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4690:16)
#67 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4840:11)
#68 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#69 StatefulElement.update (package:flutter/src/widgets/framework.dart:4872:5)
#70 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#71 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4690:16)
#72 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#73 StatelessElement.update (package:flutter/src/widgets/framework.dart:4746:5)
#74 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#75 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4690:16)
#76 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#77 StatelessElement.update (package:flutter/src/widgets/framework.dart:4746:5)
#78 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#79 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6202:14)
#80 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#81 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4690:16)
#82 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#83 ProxyElement.update (package:flutter/src/widgets/framework.dart:5020:5)
#84 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#85 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4690:16)
#86 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#87 ProxyElement.update (package:flutter/src/widgets/framework.dart:5020:5)
#88 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#89 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4690:16)
#90 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4840:11)
#91 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#92 StatefulElement.update (package:flutter/src/widgets/framework.dart:4872:5)
#93 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#94 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4690:16)
#95 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4840:11)
#96 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#97 StatefulElement.update (package:flutter/src/widgets/framework.dart:4872:5)
#98 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#99 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4690:16)
#100 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4840:11)
#101 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#102 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2620:33)
#103 WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:882:21)
#104 RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:319:5)
#105 SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1143:15)
#106 SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1080:9)
#107 SchedulerBinding.scheduleWarmUpFrame.<anonymous closure> (package:flutter/src/scheduler/binding.dart:863:7)
(elided 4 frames from class _RawReceivePortImpl, class _Timer, and dart:async-patch)
====================================================================================================
我的登录屏幕代码：
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:udemy_flutter/shared/components/components.dart';
class LoginScreen extends StatelessWidget {
var emailController = TextEditingController();
var passController = TextEditingController();
var formKey = GlobalKey<FormState>();
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(),
body: Padding(
padding: const EdgeInsets.all(20.0),
child: Center(
child: SingleChildScrollView(
child: Form(
key: formKey,
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
const Text(
'Login',
style: TextStyle(
fontSize: 40.0,
fontWeight: FontWeight.bold
),
),
const SizedBox(
height: 40.0,
),
defaultFormFeild(
controller: emailController,
label: 'Email',
prefix: Icons.email,
type: TextInputType.emailAddress,
validate: (String value){
if(value.isEmpty != null){
return 'Email Cannot Be Empty';
}
return null;
}
),
const SizedBox(
height: 15.0,
),
TextFormField(
controller: passController,
obscureText: true,
keyboardType: TextInputType.visiblePassword,
decoration: const InputDecoration(
border: OutlineInputBorder(),
labelText: 'Password',
prefixIcon: Icon(
Icons.lock
),
suffixIcon: Icon(
Icons.remove_red_eye,
)
),
onChanged: (value) {
print(value);
},
onFieldSubmitted: (value) {
print(value);
},
validator: (value) {
if(value!.isEmpty){
return 'Password cannot be empty';
}
return null;
},
),
const SizedBox(
height: 10.0,
),
defaultButton(
function: (){
print(emailController.text);
print(passController.text);
},
text: 'Login',
),
const SizedBox(
height: 10.0,
),
defaultButton(
text: 'ReGister',
function: () {
print('You have just clicked on register');
},
background: Colors.red,
isUpperCase: false
),
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: [
const Text('Don't you have an account?'),
TextButton(onPressed: () {}, child: const Text(
'Register Now'
))
],
)
],
),
),
),
),
),
);
}
}
我的主要零件代码：
import 'package:flutter/material.dart';
import 'package:udemy_flutter/modules/bmi_result/bmi_result_screen.dart';
import 'modules/bmi_result/bmi_result_screen.dart';
import 'modules/bmi/bmi_screen.dart';
import 'modules/home/home_screen.dart';
import 'modules/login/login_screen.dart';
import 'modules/messenger/messenger_screen.dart';
import 'modules/users/users_screen.dart';
import 'modules/counter/counter_screen.dart';
void main() {
runApp(MyApp());
MyApp app = MyApp();
}
//Stateless widget
//Stateful widget
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
home: LoginScreen(),
);
}
}
编辑：我在一个名为components.dart 的单独文件中有这段代码
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
Widget defaultButton(
{double width = double.infinity,
Color background = Colors.blue,
double radius = 10.0,
required Function function,
required String text,
bool isUpperCase = true}) =>
Container(
height: 40.0,
width: width,
child: MaterialButton(
onLongPress: () {},
onPressed: function(),
child: Text(
isUpperCase ? text.toUpperCase() : text.toLowerCase(),
style: TextStyle(color: Colors.white),
)),
decoration: BoxDecoration(
borderRadius: BorderRadiusDirectional.circular(radius),
color: background,
),
);
Widget defaultFormFeild({
required TextEditingController controller,
required TextInputType type,
Function? onSubmit, //Add question mark
Function? onChange, //Add question mark
required Function validate,
required var label,
required IconData prefix,
}) =>
TextFormField(
controller: controller,
keyboardType: type,
onFieldSubmitted: onSubmit != null? onSubmit() : null, //do null checking
onChanged: onChange != null? onChange() : null, //do null checking
validator: validate(),
decoration: InputDecoration(
labelText: label,
prefixIcon: Icon(prefix),
border: OutlineInputBorder()
),
);
有人能告诉我哪里出了问题吗我是Flutter平台的新手，我正在尝试构建各种用途的屏幕，因为我遇到了Null安全问题，我设法解决了它，但我不知道这个代码的问题到底是
避免在函数类型中使用纯Function：
Widget defaultFormFeild({
required TextEditingController controller,
required TextInputType type,
void Function(String)? onSubmit,
void Function(String)? onChange,
required String? Function(String) validate,
required var label,
required IconData prefix,
})
查看您在哪里使用onSubmit。如果您使用的是IDE，请将鼠标悬停在onSubmit: onSubmit上的:之前，然后查看此函数的类型。否则，请查看文档以了解onSubmit接受的类型。
对defaultButton执行相同操作。