如何解决此问题 [错误：flutter/lib/ui/ui_dart_state.cc(199)] 未处理的异常：NoSuchMethodError：在 null 上调用了 getter 'insta
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【中文标题】如何解决此问题 [错误：flutter/lib/ui/ui_dart_state.cc(199)] 未处理的异常：NoSuchMethodError：在 null 上调用了 getter \'instance\'。错误？【英文标题】：How to fix this [ERROR:flutter/lib/ui/ui_dart_state.cc(199)] Unhandled Exception: NoSuchMethodError: The getter 'instance' was called on null. error?如何解决此问题 [错误：flutter/lib/ui/ui_dart_state.cc(199)] 未处理的异常：NoSuchMethodError：在 null 上调用了 getter 'instance'。错误？ 【发布时间】：2021-09-23 13:05:06 【问题描述】：我正在尝试接收用于用户身份验证的 OTP。但是，我没有收到任何 OTP，我收到了这个错误。
这是错误：
E/flutter (30379): [错误:flutter/lib/ui/ui_dart_state.cc(199)] 未处理的异常：NoSuchMethodError：getter 'instance' 是 调用为空。 E/颤动（30379）：接收器：空 E/颤动（30379）： 尝试调用：instance E/flutter (30379): #0 Object.noSuchMethod (dart:core-patch/object_patch.dart:54:5) E/flutter (30379): #1 _OtpscreenState.verifyPhone (package:userauth/Otpscreen.dart:172:24) E/flutter (30379): #2 _OtpscreenState.initState (package:userauth/Otpscreen.dart:210:5) E/flutter (30379): #3 StatefulElement._firstBuild(package:flutter/src/widgets/framework.dart:4711:57) E/颤振（30379）：#4 ComponentElement.mount (包:flutter/src/widgets/framework.dart:4548:5) E/flutter (30379): #5 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3611:14) E/flutter (30379): #6 元素.updateChild (包:flutter/src/widgets/framework.dart:3363:18) E/flutter (30379): #7 SingleChildRenderObjectElement.mount (包:flutter/src/widgets/framework.dart:6083:14) E/flutter （30379）：#8 Element.inflateWidget (包:flutter/src/widgets/framework.dart:3611:14) E/flutter (30379): #9 元素.updateChild (包:flutter/src/widgets/framework.dart:3363:18) E/flutter （30379）：#10 ComponentElement.performRebuild (包:flutter/src/widgets/framework.dart:4599:16) E/flutter (30379): #11 元素重建 (包:flutter/src/widgets/framework.dart:4267:5) E/flutter (30379): #12 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:4553:5) E/flutter (30379): #13 ComponentElement.mount (package:flutter/src/widgets/framework.dart:4548:5) E/flutter (30379): #14 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3611:14) E/flutter (30379): #15 元素.updateChild (包:flutter/src/widgets/framework.dart:3363:18) E/flutter (30379): #16 SingleChildRenderObjectElement.mount (包:flutter/src/widgets/framework.dart:6083:14) E/flutter (30379): #17 元素.inflateWidget (包:flutter/src/widgets/framework.dart:3611:14) E/flutter (30379): #18 元素.updateChild (包:flutter/src/widgets/framework.dart:3363:18) E/flutter (30379): #19 SingleChildRenderObjectElement.mount (包:flutter/src/widgets/framework.dart:6083:14) E/flutter （30379）：#20 元素.inflateWidget (包:flutter/src/widgets/framework.dart:3611:14) E/flutter (30379): #21 元素.updateChild (包:flutter/src/widgets/framework.dart:3363:18) E/flutter （30379）：#22 ComponentElement.performRebuild (包:flutter/src/widgets/framework.dart:4599:16) E/flutter （30379）：#23 StatefulElement.performRebuild (包:flutter/src/widgets/framework.dart:4746:11) E/flutter （30379）：#24 元素重建 (包:flutter/src/widgets/framework.dart:4267:5) E/flutter (30379): #25 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:4553:5) E/flutter (30379): #26 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:4737:11) E/flutter （30379）：#27 ComponentElement.mount (包:flutter/src/widgets/framework.dart:4548:5) E/flutter (30379): #28 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3611:14) E/flutter (30379): #29 元素.updateChild (包:flutter/src/widgets/framework.dart:3363:18) E/flutter (30379): #30 SingleChildRenderObjectElement.mount (包:flutter/src/widgets/framework.dart:6083:14) E/flutter （30379）：#31 元素.inflateWidget (包:flutter/src/widgets/framework.dart:3611:14) E/flutter (30379): #32 元素.updateChild (包:flutter/src/widgets/framework.dart:3363:18) E/flutter (30379): #33 SingleChildRenderObjectElement.mount (包:flutter/src/widgets/framework.dart:6083:14) E/flutter （30379）：#34 元素.inflateWidget (包:flutter/src/widgets/framework.dart:3611:14) E/flutter (30379): #35 元素.updateChild (包:flutter/src/widgets/framework.dart:3363:18) E/flutter （30379）：#36 ComponentElement.performRebuild (包:flutter/src/widgets/framework.dart:4599:16) E/flutter （30379）：#37 StatefulElement.performRebuild (包:flutter/src/widgets/framework.dart:4746:11) E/flutter （30379）：#38 元素重建 (包:flutter/src/widgets/framework.dart:4267:5) E/flutter (30379): #39 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:4553:5) E/flutter (30379): #40 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:4737:11) E/flutter (30379): #41 组件元素.mount (包:flutter/src/widgets/framework.dart:4548:5) E/flutter (30379): #42 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3611:14) E/flutter (30379): #43 元素.updateChild (包:flutter/src/widgets/framework.dart:3363:18) E/flutter （30379）：#44 ComponentElement.performRebuild (包:flutter/src/widgets/framework.dart:4599:16)
这是我的代码：
import 'package:flutter/material.dart';
import 'package:pinput/pin_put/pin_put.dart';
import 'package:pinput/pin_put/pin_put_state.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:userauth/Profilescreen.dart';
class Otpscreen extends StatefulWidget
String phone;
Otpscreen(this.phone);
@override
_OtpscreenState createState() => _OtpscreenState();
class _OtpscreenState extends State<Otpscreen>
final GlobalKey<ScaffoldState> _scaffoldkey = GlobalKey<ScaffoldState>();
late String otp;
late String _verificationCode;
final TextEditingController _pinPutController = TextEditingController();
final FocusNode _pinPutFocusNode = FocusNode();
final BoxDecoration pinPutDecoration = BoxDecoration(
color: Colors.blue,
borderRadius: BorderRadius.circular(10.0),
border: Border.all(
color: const Color.fromRGBO(126, 203, 224, 1),
),
);
@override
Widget build(BuildContext context)
return Scaffold(
body: SafeArea(
child: Column(
children: [
Expanded(
child: Padding(
padding: const EdgeInsets.only(top: 10, bottom: 10),
child: Column(
children: [
Padding(
padding: const EdgeInsets.only(right: 310),
child: RawMaterialButton(
onPressed: ()
Navigator.pop(context, "phone");
,
child: Icon(Icons.arrow_back),
),
),
SizedBox(height: 40),
Text(
"Verify Phone",
style: TextStyle(
fontWeight: FontWeight.bold,
fontSize: 20,
color: Colors.black),
),
SizedBox(height: 10),
Text(
"code is sent to $widget.phone",
style: TextStyle(
fontSize: 14,
fontWeight: FontWeight.w500,
color: Colors.grey),
),
Padding(
padding: const EdgeInsets.all(30.0),
child: PinPut(
fieldsCount: 6,
textStyle: const TextStyle(
fontSize: 25.0, color: Colors.white),
eachFieldWidth: 40.0,
eachFieldHeight: 55.0,
focusNode: _pinPutFocusNode,
controller: _pinPutController,
submittedFieldDecoration: pinPutDecoration,
selectedFieldDecoration: pinPutDecoration,
followingFieldDecoration: pinPutDecoration,
pinAnimationType: PinAnimationType.fade,
onSubmit: (pin) async
try
await FirebaseAuth.instance
.signInWithCredential(
PhoneAuthProvider.credential(
verificationId: _verificationCode,
smsCode: pin))
.then((value) async
if (value.user != null)
Navigator.pushAndRemoveUntil(
context,
MaterialPageRoute(
builder: (context) => Profilescreen()),
(route) => false);
);
catch (e)
FocusScope.of(context).unfocus();
_scaffoldkey.currentState!.showSnackBar(
SnackBar(content: Text("invalid OTP")));
,
),
),
SizedBox(
height: 20,
),
Center(
child: Padding(
padding: const EdgeInsets.only(
left: 20, right: 20, top: 0, bottom: 10),
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Center(
child: Text(
"Didn't receive an code?",
),
),
GestureDetector(
onTap: ()
Navigator.pushNamed(context, "phone");
,
child: Center(
child: Text(
"Request Again",
style: TextStyle(
color: Colors.black,
fontWeight: FontWeight.bold,
fontSize: 16,
),
),
),
),
],
),
),
),
SizedBox(height: 20),
RawMaterialButton(
onPressed: ()
Navigator.pushNamed(context, "profile");
,
fillColor: Colors.blue,
child: Padding(
padding: const EdgeInsets.fromLTRB(50, 15, 50, 15),
child: Text(
"VERIFY AND CONTINUE",
style: TextStyle(
fontSize: 16, fontWeight: FontWeight.bold),
),
),
),
],
),
),
),
],
),
),
);
verifyPhone() async
var firebaseAuth;
var widget;
await firebaseAuth.instance.verifyPhoneNumber(
phoneNumber: "+91$widget.phone",
verificationCompleted: (PhoneAuthCredential credential) async
await firebaseAuth.instance
.signInCredential(credential)
.then((value) async
if (value.user > 0)
Navigator.pushAndRemoveUntil(
context,
MaterialPageRoute(builder: (context) => Profilescreen()),
(route) => false);
);
,
verificationFailed: (FirebaseAuthException e)
print(e.message);
,
codesent: (String verificationID, int resendToken)
setState(()
_verificationCode = verificationID;
);
,
codeAutoRetrievalTimeout: (String verificationID)
setState(()
var verificationCode = verificationID;
);
,
timeout: Duration(seconds: 60));
@override
void initState()
// TODO: implement initState
super.initState();
verifyPhone();
谢谢！
【问题讨论】：
【参考方案1】：这是错误：
var firebaseAuth;
var widget;
await firebaseAuth.instance.verifyPhoneNumber(
phoneNumber: "+91$widget.phone",
verificationCompleted: (PhoneAuthCredential credential) async
await firebaseAuth.instance
firebaseAuth 没有引用任何对象，因此您得到：
getter 'instance' 在 null 上被调用。
因此，删除不需要的变量，并且由于属性instance 返回static FirebaseAuth，那么您必须执行以下操作：
var widget;
await FirebaseAuth.instance.verifyPhoneNumber(
phoneNumber: "+91$widget.phone",
verificationCompleted: (PhoneAuthCredential credential) async
await FirebaseAuth.instance
【讨论】：
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