Flutter：方法'/'在null上被调用。接收方：null尝试调用：/(1080.0）
由于使用 Media Query （媒体查询）设置响应式用户界面，因此出现此错误。下面是我在终端中遇到的错误。
我不知道哪个方法调用根据Dart返回null。因为我正在通过“升高按钮”导航到新屏幕，并且在我在按钮的 onPressed 上调用的 Widget / Class的构造函数上显示了此错误，
这是我从那里导航到新的医生登录屏幕的班级代码：
import 'dart:io';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:medkit/animations/fadeAnimation.dart';
import 'package:medkit/animations/bottomAnimation.dart';
import 'package:medkit/doctor/doctorLogin.dart';
import 'package:medkit/doctor/doctorPanel.dart';
import 'aboutUs.dart';
class UserType extends StatelessWidget {
@override
Widget build(BuildContext context) {
double width = MediaQuery.of(context).size.width;
double height = MediaQuery.of(context).size.height;
Future<bool> _onWillPop() async {
return (await showDialog(
context: context,
builder: (context) => new AlertDialog(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(12)
),
title: new Text(
"Exit Application",
style: TextStyle(fontWeight: FontWeight.bold),
),
content: new Text("Are You Sure?"),
actions: <Widget>[
// usually buttons at the bottom of the dialog
FlatButton(
shape: StadiumBorder(),
color: Colors.white,
child: new Text(
"Close",
style: TextStyle(color: Colors.blue),
),
onPressed: () {
Navigator.of(context).pop();
},
),
FlatButton(
shape: StadiumBorder(),
color: Colors.white,
child: new Text(
"Yes",
style: TextStyle(color: Colors.red),
),
onPressed: () {
exit(0);
},
),
],
),
)) ??
false;
}
return WillPopScope(
onWillPop: _onWillPop,
child: Scaffold(
body: SafeArea(
child: Padding(
padding: EdgeInsets.symmetric(horizontal: width * 0.04),
child: Column(
children: <Widget>[
SizedBox(
height: height * 0.08,
),
FadeAnimation(
0.3,
Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
Text(
'Category',
style: TextStyle(color: Colors.black, fontSize: 30),
),
GestureDetector(
onTap: () => _exitAlert(context),
child: Icon(
Icons.exit_to_app,
size: height * 0.04,
),
)
],
),
),
SizedBox(height: height * 0.09),
Column(
children: <Widget>[
FadeAnimation(
0.4,
CircleAvatar(
backgroundColor: Colors.black.withOpacity(0.2),
radius: height * 0.075,
child: Image(image: AssetImage("assets/doctor.png")),
),
),
WidgetAnimator(patDocBtn('Doctor', context)),
SizedBox(
height: height * 0.1,
),
FadeAnimation(
0.4,
CircleAvatar(
backgroundColor: Colors.black.withOpacity(0.2),
radius: height * 0.075,
child: Image(image: AssetImage("assets/patient.png")),
),
),
WidgetAnimator(patDocBtn('Patient', context)),
SizedBox(height: height * 0.13,),
GestureDetector(
onTap: () => Navigator.push(context, new MaterialPageRoute(builder: (context) => AboutUs())),
child: Column(
children: <Widget>[
Text('Version', style: TextStyle(fontWeight: FontWeight.bold),),
Text('V 0.1', style: TextStyle(fontSize: 12),)
],
),
),
SizedBox(height: 5,)
],
)
],
),
),
),
),
);
}
Widget patDocBtn(String categoryText, context) {
return Container(
width: MediaQuery.of(context).size.width * 0.5,
child: RaisedButton(
onPressed: () {
if (categoryText == 'Doctor') {
Navigator.pushNamed(context, 'DoctorLogin');
} else {
Navigator.pushNamed(context, 'PatientLogin');
}
},
color: Colors.white,
child: Text("I am " + categoryText),
shape: StadiumBorder(),
),
);
}
_exitAlert(context) {
showDialog(
context: context,
builder: (BuildContext context) {
return AlertDialog(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(12)
),
title: new Text(
"Exit Application",
style: TextStyle(fontWeight: FontWeight.bold),
),
content: new Text("Are You Sure?"),
actions: <Widget>[
// usually buttons at the bottom of the dialog
FlatButton(
color: Colors.white,
child: new Text(
"Close",
style: TextStyle(color: Colors.blue),
),
onPressed: () {
Navigator.of(context).pop();
},
),
FlatButton(
color: Colors.white,
child: new Text(
"Yes",
style: TextStyle(color: Colors.red),
),
onPressed: () {
exit(0);
},
),
],
);
},
);
}
}
这是医生的登录课程代码
import 'dart:math';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter_screenutil/flutter_screenutil.dart';
import 'package:google_fonts/google_fonts.dart';
import 'package:google_sign_in/google_sign_in.dart';
import 'package:medkit/animations/fadeAnimation.dart';
import 'package:medkit/animations/bottomAnimation.dart';
import 'package:medkit/doctor/doctorPanel.dart';
import 'package:medkit/otherWidgetsAndScreen/backBtn.dart';
import 'package:medkit/otherWidgetsAndScreen/imageAvatar.dart';
import 'package:toast/toast.dart';
class DoctorLogin extends StatefulWidget {
@override
_DoctorLoginState createState() => _DoctorLoginState();
}
class _DoctorLoginState extends State<DoctorLogin> {
final FirebaseAuth _firebaseAuth = FirebaseAuth.instance;
final GoogleSignIn _googleSignIn = new GoogleSignIn();
Future<FirebaseUser> _signIn(BuildContext context) async {
final GoogleSignInAccount googleUser = await _googleSignIn.signIn();
final GoogleSignInAuthentication googleAuth =
await googleUser.authentication;
final AuthCredential credential = GoogleAuthProvider.getCredential(
idToken: googleAuth.idToken, accessToken: googleAuth.accessToken);
FirebaseUser userDetails =
await _firebaseAuth.signInWithCredential(credential);
ProviderDoctorDetails providerInfo =
new ProviderDoctorDetails(userDetails.providerId);
List<ProviderDoctorDetails> providerData =
new List<ProviderDoctorDetails>();
providerData.add(providerInfo);
DoctorDetails details = new DoctorDetails(
userDetails.providerId,
userDetails.displayName,
userDetails.photoUrl,
userDetails.email,
providerData,
);
Navigator.push(
context,
new MaterialPageRoute(
builder: (context) => DoctorPanel(
detailsUser: details,
)));
return userDetails;
}
@override
Widget build(BuildContext context) {
final nameTextFieldController = TextEditingController();
final nameTextField = TextField(
keyboardType: TextInputType.text,
autofocus: false,
maxLength: 30,
textInputAction: TextInputAction.next,
onSubmitted: (_) => FocusScope.of(context).nextFocus(),
controller: nameTextFieldController,
decoration: InputDecoration(
fillColor: Colors.black.withOpacity(0.07),
filled: true,
labelText: 'Enter Name',
prefixIcon: Icon(Icons.person),
border: OutlineInputBorder(
borderRadius: const BorderRadius.all(const Radius.circular(20)))),
);
final phNumberTextController = TextEditingController();
final phoneTextField = TextField(
keyboardType: TextInputType.phone,
autofocus: false,
maxLength: 11,
controller: phNumberTextController,
textInputAction: TextInputAction.next,
onSubmitted: (_) => FocusScope.of(context).nextFocus(),
decoration: InputDecoration(
filled: true,
fillColor: Colors.black.withOpacity(0.07),
labelText: 'Enter Number',
prefixIcon: Icon(Icons.phone),
border: new OutlineInputBorder(
borderRadius: const BorderRadius.all(const Radius.circular(20)),
),
),
);
final cnicTextController = TextEditingController();
final cnicTextField = TextFormField(
keyboardType: TextInputType.number,
autofocus: false,
maxLength: 13,
controller: cnicTextController,
decoration: InputDecoration(
filled: true,
fillColor: Colors.black.withOpacity(0.07),
labelText: 'Enter CNIC',
prefixIcon: Icon(Icons.card_membership),
border: OutlineInputBorder(borderRadius: BorderRadius.circular(20))),
);
final double width = MediaQuery.of(context).size.width;
final double height = MediaQuery.of(context).size.height;
return GestureDetector(
onTap: () {
FocusScopeNode currentFocus = FocusScope.of(context);
if (!currentFocus.hasPrimaryFocus) {
currentFocus.unfocus();
}
},
child: Scaffold(
resizeToAvoidBottomPadding: false,
body: SafeArea(
child: Container(
width: width,
height: height,
child: Stack(
children: <Widget>[
ImageAvatar(
assetImage: 'assets/bigDoc.png',
),
Container(
width: width,
height: height,
margin: EdgeInsets.fromLTRB(width * 0.03, 0, width * 0.03, 0),
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
BackBtn(),
SizedBox(height: height * 0.05,),
Text(
"\t\tLogin",
style: GoogleFonts.abel(
fontSize: ScreenUtil.instance.setSp(35),
fontWeight: FontWeight.bold),
),
SizedBox(
height: height * 0.05,
),
WidgetAnimator(nameTextField),
WidgetAnimator(phoneTextField),
WidgetAnimator(cnicTextField),
SizedBox(height: height * 0.01,),
FadeAnimation(
1.5,
SizedBox(
width: width,
height: height * 0.07,
child: RaisedButton(
color: Colors.white,
shape: StadiumBorder(),
onPressed: () {
if (nameTextFieldController.text != "" ||
phNumberTextController.text != "" ||
cnicTextController.text != "") {
Firestore.instance
.collection('doctorInfo')
.document(nameTextFieldController.text)
.setData({
'cnic': cnicTextController.text,
'phoneNumber': phNumberTextController.text,
});
_signIn(context)
.then((FirebaseUser user) =>
print('Gmail Logged In'))
.catchError((e) => print(e));
nameTextFieldController.clear();
cnicTextController.clear();
phNumberTextController.clear();
} else {
Toast.show('Fields Cannot be Empty!', context,
backgroundColor: Colors.red,
gravity: Toast.CENTER,
duration: Toast.LENGTH_SHORT);
}
},
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Image(
image: AssetImage('assets/google.png'),
height: ScreenUtil.instance.setHeight(35),
),
SizedBox(width: ScreenUtil.instance.setWidth(15)),
Text(
'Login',
style: TextStyle(
letterSpacing: 2,
fontWeight: FontWeight.bold,
fontSize: ScreenUtil.instance.setSp(18)),
)
],
),
),
),
),
SizedBox(height: height * 0.02,),
FadeAnimation(
2,
Text(
'You Will be asked Question regarding your Qualifications!', textAlign: TextAlign.center,
style: TextStyle(color: Colors.black.withOpacity(0.5),),
),
),
],
),
),
],
),
),
)),
);
}
}
class DoctorDetails {
final String providerDetails;
final String userName;
final String photoUrl;
final String userEmail;
final List<ProviderDoctorDetails> providerData;
DoctorDetails(this.providerDetails, this.userName, this.photoUrl,
this.userEmail, this.providerData);
}
class ProviderDoctorDetails {
ProviderDoctorDetails(this.providerDetails);
final String providerDetails;
}
2 个答案:
答案 0 :(得分：0)
解决方案
我同时使用Media Query和第三方依赖。我刚刚在代码中删除了Dependency及其用法，就解决了
结论 可能您无法同时使用Media Query和第三方依赖项来使您的应用程序具有响应性
答案 1 :(得分：0)
您的pushNamed路由，路由名称以'/'开头？您是否将其声明为“ / NAMEOFTHEROUTE”？ 如果是，请使用您的pushNamed作为“ / NAMEOFTHEROUTE”。
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