首先，我是Flutter的初学者。我正在发送表单数据以登录API，并等待成功：来自API的OK消息和UserID。
获取UserID和成功后：API的响应正确，我使用userID将用户发送到仪表板这是我的完整代码；
class LoginScreen1 extends StatefulWidget {
@override
_LoginScreen1State createState() => _LoginScreen1State();
}
class _LoginScreen1State extends State<LoginScreen1> {
StreamSubscription streamSubscription;
String formMail, formSifre;
final _usernameController = TextEditingController();
final _passwordController = TextEditingController();
final formKey = GlobalKey<FormState>();
Login login;
Future<Login> _gonderiGetir(String formMail, String formSifre) async {
var url = 'MYURL';
var apiKey = "MYKEY";
var authPassword = this.formSifre;
var authMail = this.formMail;
debugPrint(this.formSifre);
var response = await http
.get('$url?Key=12345&mail=${this.formMail}&password=${this.formSifre}');
debugPrint("Sonuç Bekleniyor.");
if (response.statusCode == 200) {
_gelenDegeriBekle();
return Login.fromJsonMap(json.decode(response.body));
} else {
throw Exception("Baglanamadık ${response.statusCode}");
}
}
@override
void initState() {
// TODO: implement initState
super.initState();
/*_gonderiGetir(formSifre, formMail).then((gelenDeger) {
login = gelenDeger;
debugPrint(login.UserID);
});*/
}
@override
Widget build(BuildContext context) {
return Scaffold(
body: Container(
color: Color(0xFFF7F8FA),
child: ListView(
children: <Widget>[
Stack(
children: <Widget>[
Container(
height: 250.0,
width: double.infinity,
),
Container(
height: 300.0,
width: double.infinity,
color: Color(0xFFFED428),
),
Positioned(
top: 225.0,
left: 15.0,
right: 15.0,
child: Material(
elevation: 3.0,
borderRadius: BorderRadius.circular(7.0),
child: Container(
height: 280.0,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(7.0),
color: Color(0xF6F6F6)),
),
)),
Positioned(
top: 75.0,
left: (MediaQuery.of(context).size.width / 2 - 50.0),
child: CircleAvatar(
radius: 50.0,
backgroundImage: NetworkImage(
"https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSHVRLWSF79r7ABstLzXZi_pTcNkAMqx8EtWfIRZiA8mmqcl-Fsqw"),
),
),
Padding(
padding: const EdgeInsets.fromLTRB(40, 235, 40, 15),
child: Form(
key: formKey,
autovalidate: true,
child: Column(
children: <Widget>[
TextFormField(
decoration: const InputDecoration(
labelStyle: TextStyle(color: Color(0xFFBBBFCB)),
icon: Icon(
Icons.person,
color: Color(0xFFBBBFCB),
),
labelText: 'Email *',
),
validator: (String girilenVeri) {
if (!girilenVeri.contains("@")) {
return "Geçerli bir mail adresi giriniz.";
} else
return null;
},
controller: _usernameController,
onSaved: (deger) => formMail = deger,
),
SizedBox(
height: 10.0,
),
TextFormField(
obscureText: true,
decoration: const InputDecoration(
labelStyle: TextStyle(color: Color(0xFFBBBFCB)),
icon: Icon(
Icons.lock,
color: Color(0xFFBBBFCB),
),
labelText: 'Şifre *',
),
validator: (String girilenVeri) {
if (girilenVeri.length < 6) {
return "Şifre 6 karakterden kısa olamaz.";
} else
return null;
},
controller: _passwordController,
onSaved: (deger) => formSifre = deger,
),
],
),
),
),
Padding(
padding: const EdgeInsets.fromLTRB(40, 420, 40, 15),
child: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
SizedBox(
width: double.infinity,
height: 50,
child: RaisedButton(
elevation: 0,
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(10.0)),
color: Color(0xFFFED428),
onPressed: () {
if (formKey.currentState.validate()) {
formKey.currentState.save();
_gonderiGetir(formMail, formSifre);
debugPrint("OnPress Geldi");
}
},
child: Text(
"GİRİŞ",
style: TextStyle(fontSize: 20),
),
),
),
FlatButton(
onPressed: () {},
child: Text(
"Şifremi Unuttum",
style: TextStyle(
fontSize: 10, color: Color(0xFFBBBFCB)),
),
)
],
),
),
),
],
)
],
),
),
);
;
}
void _loginControl() {
if (formKey.currentState.validate()) {
formKey.currentState.save();
//formMail = _usernameController.text;
//formSifre= _passwordController.text;
debugPrint("$formSifre ve $formMail");
}
}
void _gelenDegeriBekle() {
_gonderiGetir(formSifre, formMail).then((gelenDeger) {
login = gelenDeger;
if (login.Status != null) {
debugPrint(login.UserID);
debugPrint(login.Status);
Navigator.pushReplacement(
context,
MaterialPageRoute(
builder: (context) => MyHomePage(),
),
);
}
});
}
}
但是我遇到了这个循环错误：
flutter: asdasd
flutter: 387ddd00-f5ed-4c9c-87cf-45835bf77a53
flutter: OK
[VERBOSE-2:ui_dart_state.cc(148)] Unhandled Exception: NoSuchMethodError: The method 'ancestorStateOfType' was called on null.
Receiver: null
Tried calling: ancestorStateOfType(Instance of 'TypeMatcher<NavigatorState>')
#0 Object.noSuchMethod (dart:core/runtime/libobject_patch.dart:50:5)
#1 Navigator.of (package:flutter/src/widgets/navigator.dart:1376:19)
#2 Navigator.pushReplacement (package:flutter/src/widgets/navigator.dart:1055:22)
#3 _LoginScreen1State._gelenDegeriBekle.<anonymous closure> (package:flutter_apppp/login.dart:247:19)
#4 _rootRunUnary (dart:async/zone.dart:1132:38)
#5 _CustomZone.runUnary (dart:async/zone.dart:1029:19)
#6 _FutureListener.handleValue (dart:async/future_impl.dart:126:18)
#7 Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:639:45)
#8 Future._propagateToListeners (dart:async/future_impl.dart:668:32)
#9 Future._complete (dart:async/future_impl.dart:473:7)
#10 _SyncCompleter.complete (dart:<…>
我一直收到此错误消息。
答案 0 :(得分：0)
看起来您有一个循环在您的小部件中连续运行。您正在从_gonderiGetir呼叫_gelenDegeriBekle，也正在从_gelenDegeriBekle呼叫_gonderiGetir。因此，即使您的小部件已删除，它也将永远保持下去（这就是context为null的原因。）
如果您需要连续做某事，我建议改为使用定期计时器来调用它，并确保在处置小部件时停止计时器！