不断收到此错误：
<块引用>NoSuchMethodError: getter 'uid' 在 null flutter 上被调用。
自定义抽屉代码
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:rideboard/models/user.dart';
import 'package:rideboard/services/database.dart';
import 'package:rideboard/ui/components/constants.dart';
import 'package:rideboard/ui/components/custom_button.dart';
import 'package:rideboard/services/auth.dart';
final AuthService _mypagedrawerservice = AuthService();
// ignore: must_be_immutable
class MyDrawer extends StatelessWidget {
@override
Widget build(BuildContext context) {
final user = Provider.of<MyUser>(context);
print(user.uid);
return StreamBuilder<UserData>(
stream: DatabaseService(uid: user.uid).userData,
// ignore: missing_return
builder: (context, snapshot) {
if (snapshot.hasData) {
// ignore: unused_local_variable
UserData userData = snapshot.data;
return Drawer(
child: Container(
child: ListView(
children: [
Stack(
children: [
Container(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
CircleAvatar(
backgroundImage:
AssetImage('assets/my_picture.jpg'),
radius: 70),
SizedBox(height: 20),
Text(
userData.firstname,
style: TextStyle(
fontSize: 25, fontWeight: FontWeight.bold),
),
],
),
height: 230,
width: double.infinity,
decoration: BoxDecoration(
image: DecorationImage(
image: AssetImage('assets/PATTERN3.png'),
fit: BoxFit.cover),
),
),
],
),
Column(
children: [
SizedBox(height: 20),
ListTile(
title: new Row(children: [
SizedBox(
width: 45,
),
Text('Profile', style: kiconTexts),
]),
leading: Icon(Icons.account_box, size: 23),
onTap: () {},
),
SizedBox(height: 15),
ListTile(
title: new Row(children: [
SizedBox(
width: 45,
),
Text('Filters', style: kiconTexts),
]),
leading: Icon(Icons.drag_indicator_rounded, size: 23),
onTap: () {},
),
SizedBox(height: 15),
ListTile(
title: new Row(children: [
SizedBox(
width: 12,
),
Text('Ride/Trip History', style: kiconTexts),
]),
leading: Icon(Icons.history, size: 23),
onTap: () {},
),
SizedBox(height: 15),
ListTile(
title: new Row(children: [
SizedBox(
width: 40,
),
Text('Payment', style: kiconTexts),
]),
leading: Icon(Icons.payment_rounded, size: 23),
onTap: () {},
),
SizedBox(height: 15),
ListTile(
title: new Row(children: [
SizedBox(
width: 40,
),
Text('Settings', style: kiconTexts),
]),
leading: Icon(Icons.settings, size: 23),
onTap: () {},
),
SizedBox(height: 80),
CustomButton1(
colorChoice: kthemeColor.withOpacity(0.9),
yourConstraints:
BoxConstraints.expand(width: 120, height: 45),
widgetChoice: Text(
'Log Out',
style: kMyName,
),
whenPressed: () {
_mypagedrawerservice.signOut().then((_) {
Navigator.of(context).pushNamedAndRemoveUntil(
'/Login', ModalRoute.withName('/Rider'));
});
},
)
],
),
],
),
));
}
});
}
}
包装代码
import 'package:flutter/material.dart';
import 'package:rideboard/ui/Screens/Rider_page.dart';
import 'package:rideboard/ui/authenticate/authenticate.dart';
import 'package:rideboard/models/user.dart';
import 'package:provider/provider.dart';
class Wrapper extends StatelessWidget {
@override
Widget build(BuildContext context) {
// return either the authenticate or the driver or rider screen
var user = Provider.of<MyUser>(context);
if (user == null) {
return Authenticate();
} else {
print(user.uid);
return RiderPage();
}
}
}
Main.dart 代码
import 'dart:async';
import 'package:firebase_core/firebase_core.dart';
import 'package:flutter/material.dart';
import 'package:flutter_spinkit/flutter_spinkit.dart';
import 'package:rideboard/route_generator.dart';
import 'package:rideboard/services/appData.dart';
import 'package:rideboard/services/auth.dart';
import 'ui/Screens/Login_Screen.dart';
import 'ui/components/constants.dart';
import 'package:provider/provider.dart';
import 'models/user.dart';
void main() async {
WidgetsFlutterBinding.ensureInitialized();
await Firebase.initializeApp();
runApp(Rideboard());
}
class Rideboard extends StatelessWidget {
@override
Widget build(BuildContext context) {
return ChangeNotifierProvider(
create: (context) => AppData(),
child: StreamProvider<MyUser>.value(
value: AuthService().user,
child: MaterialApp(
initialRoute: "/Wrapper",
onGenerateRoute: RouteGenerator.generateRoute,
debugShowCheckedModeBanner: false,
theme: ThemeData(
scaffoldBackgroundColor: kthemeColor.withOpacity(0.2),
textTheme: ktextTheme,
),
),
),
);
}
}
class LoadingScreen extends StatefulWidget {
static const String id = 'LoadingScreen';
@override
_LoadingScreenState createState() => _LoadingScreenState();
}
class _LoadingScreenState extends State<LoadingScreen> {
//Initializes the Timer
@override
void initState() {
super.initState();
Timer(
Duration(seconds: 20),
() => Navigator.push(
context,
MaterialPageRoute(
builder: (context) => LoginScreen(),
),
),
);
}
@override
Widget build(BuildContext context) {
return Scaffold(
body: Stack(
fit: StackFit.expand,
children: [
Container(
decoration: BoxDecoration(
image: DecorationImage(
image: AssetImage(
'assets/PATTERN3.png',
),
fit: BoxFit.cover),
),
),
Column(
mainAxisAlignment: MainAxisAlignment.spaceAround,
children: [
SizedBox(height: 20),
Image.asset(
'assets/logo.png',
scale: 4.5,
),
Text('Hitch a ride Asap!', style: kSplashScreen),
SizedBox(height: 30),
SpinKitWave(
itemBuilder: (context, index) {
return DecoratedBox(
decoration: BoxDecoration(
color: index.isEven ? Color(0xFF0A1768) : Colors.blue,
),
);
},
),
SizedBox(
height: 30,
),
Text('By Myname', style: kMyName)
],
)
],
));
}
}
路由设置
import 'package:flutter/material.dart';
import 'package:rideboard/ui/Screens/Driver_Screen1.dart';
import 'package:rideboard/ui/Screens/Getting_Started.dart';
import 'package:rideboard/ui/Screens/Login_Screen.dart';
import 'package:rideboard/ui/Screens/MakeAChoiceScreen.dart';
import 'package:rideboard/ui/Screens/Rider_page.dart';
import 'package:rideboard/ui/Screens/Search_Screen.dart';
import 'package:rideboard/ui/Screens/Sign_Up.dart';
import 'ui/Screens/wrapper.dart';
class RouteGenerator {
static Route<dynamic> generateRoute(RouteSettings settings) {
switch (settings.name) {
case '/Wrapper':
return MaterialPageRoute(builder: (_) => Wrapper());
case '/Login':
return MaterialPageRoute(builder: (_) => LoginScreen());
case '/SignUp':
return MaterialPageRoute(builder: (_) => SignUpPage());
case '/GettingStarted':
return MaterialPageRoute(builder: (_) => GettingStarted());
case "/Rider":
return MaterialPageRoute(builder: (_) => RiderPage());
case "/Choice":
return MaterialPageRoute(builder: (_) => MakeAChoice());
case "/Drive":
return MaterialPageRoute(builder: (_) => DriverApp());
case "/Search":
return MaterialPageRoute(builder: (_) => SearchScreen());
}
}
}
错误：
I/flutter ( 8598): This is your address::1634, Carter Lane,
Woodbridge, Virginia I/flutter ( 8598): ══╡ EXCEPTION CAUGHT BY
WIDGETS LIBRARY
╞═══════════════════════════════════════════════════════════ I/flutter
( 8598): The following NoSuchMethodError was thrown building
MyDrawer(dirty, dependencies: I/flutter ( 8598):
[_InheritedProviderScope<MyUser>]): I/flutter ( 8598): The getter
'uid' was called on null. I/flutter ( 8598): Receiver: null I/flutter
( 8598): Tried calling: uid I/flutter ( 8598): I/flutter ( 8598): The
relevant error-causing widget was: I/flutter ( 8598): MyDrawer
I/flutter ( 8598):
file:///D:/App%20Development/Main%20Projects/rideboard/lib/ui/Screens/Rider_page.dart:100:16
I/flutter ( 8598): I/flutter ( 8598): When the exception was thrown,
this was the stack: I/flutter ( 8598): #0 Object.noSuchMethod
(dart:core-patch/object_patch.dart:51:5) I/flutter ( 8598): #1
MyDrawer.build (package:rideboard/ui/components/Mydrawer.dart:16:16)
I/flutter ( 8598): #2 StatelessElement.build
(package:flutter/src/widgets/framework.dart:4749:28) I/flutter (
8598): #3 ComponentElement.performRebuild
(package:flutter/src/widgets/framework.dart:4675:15) I/flutter (
8598): #4 Element.rebuild
(package:flutter/src/widgets/framework.dart:4369:5) I/flutter ( 8598):
#5 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:4654:5) I/flutter ( 8598):
#6 ComponentElement.mount (package:flutter/src/widgets/framework.dart:4649:5) I/flutter ( 8598):
... Normal element mounting (42 frames) I/flutter ( 8598): #48
Element.inflateWidget
(package:flutter/src/widgets/framework.dart:3615:14) I/flutter (
8598): #49 MultiChildRenderObjectElement.mount
(package:flutter/src/widgets/framework.dart:6282:32) I/flutter (
8598): ... Normal element mounting (4 frames) I/flutter ( 8598):
#53 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3615:14) I/flutter (
8598): #54 Element.updateChild
(package:flutter/src/widgets/framework.dart:3377:20) I/flutter (
8598): #55 SingleChildRenderObjectElement.update
(package:flutter/src/widgets/framework.dart:6171:14) I/flutter (
8598): #56 Element.updateChild
(package:flutter/src/widgets/framework.dart:3367:15) I/flutter (
8598): #57 ComponentElement.performRebuild
(package:flutter/src/widgets/framework.dart:4700:16) I/flutter (
8598): #58 StatefulElement.performRebuild
(package:flutter/src/widgets/framework.dart:4847:11) I/flutter (
8598): #59 Element.rebuild
(package:flutter/src/widgets/framework.dart:4369:5) I/flutter ( 8598):
#60 StatefulElement.update (package:flutter/src/widgets/framework.dart:4879:5) I/flutter ( 8598):
#61 Element.updateChild (package:flutter/src/widgets/framework.dart:3367:15) I/flutter (
8598): #62 ComponentElement.performRebuild
(package:flutter/src/widgets/framework.dart:4700:16) I/flutter (
8598): #63 Element.rebuild
(package:flutter/src/widgets/framework.dart:4369:5) I/flutter ( 8598):
#64 StatelessElement.update (package:flutter/src/widgets/framework.dart:4756:5) I/flutter ( 8598):
#65 Element.updateChild (package:flutter/src/widgets/framework.dart:3367:15) I/flutter (
8598): #66 Element.inflateWidget
(package:flutter/src/widgets/framework.dart:3605:39) I/flutter (
8598): #67 Element.updateChild
(package:flutter/src/widgets/framework.dart:3377:20) I/flutter (
8598): #68 ComponentElement.performRebuild
(package:flutter/src/widgets/framework.dart:4700:16) I/flutter (
8598): #69 Element.rebuild
(package:flutter/src/widgets/framework.dart:4369:5) I/flutter ( 8598):
#70 ProxyElement.update (package:flutter/src/widgets/framework.dart:5033:5) I/flutter ( 8598):
#71 Element.updateChild (package:flutter/src/widgets/framework.dart:3367:15) I/flutter (
8598): #72 ComponentElement.performRebuild
(package:flutter/src/widgets/framework.dart:4700:16) I/flutter (
8598): #73 StatefulElement.performRebuild
(package:flutter/src/widgets/framework.dart:4847:11) I/flutter (
8598): #74 Element.rebuild
(package:flutter/src/widgets/framework.dart:4369:5) I/flutter ( 8598):
#75 StatefulElement.update (package:flutter/src/widgets/framework.dart:4879:5) I/flutter ( 8598):
#76 Element.updateChild (package:flutter/src/widgets/framework.dart:3367:15) I/flutter (
8598): #77 ComponentElement.performRebuild
(package:flutter/src/widgets/framework.dart:4700:16) I/flutter (
8598): #78 Element.rebuild
(package:flutter/src/widgets/framework.dart:4369:5) I/flutter ( 8598):
#79 ProxyElement.update (package:flutter/src/widgets/framework.dart:5033:5) I/flutter ( 8598):
#80 Element.updateChild (package:flutter/src/widgets/framework.dart:3367:15) I/flutter (
8598): #81 ComponentElement.performRebuild
(package:flutter/src/widgets/framework.dart:4700:16) I/flutter (
8598): #82 Element.rebuild
(package:flutter/src/widgets/framework.dart:4369:5) I/flutter ( 8598):
#83 ProxyElement.update (package:flutter/src/widgets/framework.dart:5033:5) I/flutter ( 8598):
#84 Element.updateChild (package:flutter/src/widgets/framework.dart:3367:15) I/flutter (
8598): #85 RenderObjectElement.updateChildren
(package:flutter/src/widgets/framework.dart:5693:32) I/flutter (
8598): #86 MultiChildRenderObjectElement.update
(package:flutter/src/widgets/framework.dart:6293:17) I/flutter (
8598): #87 Element.updateChild
(package:flutter/src/widgets/framework.dart:3367:15) I/flutter (
8598): #88 ComponentElement.performRebuild
(package:flutter/src/widgets/framework.dart:4700:16) I/flutter (
8598): #89 StatefulElement.performRebuild
(package:flutter/src/widgets/framework.dart:4847:11) I/flutter (
8598): #90 Element.rebuild
(package:flutter/src/widgets/framework.dart:4369:5) I/flutter ( 8598):
#91 StatefulElement.update (package:flutter/src/widgets/framework.dart:4879:5) I/flutter ( 8598):
#92 Element.updateChild (package:flutter/src/widgets/framework.dart:3367:15) I/flutter (
8598): #93 ComponentElement.performRebuild
(package:flutter/src/widgets/framework.dart:4700:16) I/flutter (
8598): #94 Element.rebuild
(package:flutter/src/widgets/framework.dart:4369:5) I/flutter ( 8598):
#95 ProxyElement.update (package:flutter/src/widgets/framework.dart:5033:5) I/flutter ( 8598):
#96 Element.updateChild (package:flutter/src/widgets/framework.dart:3367:15) I/flutter (
8598): #97 ComponentElement.performRebuild
(package:flutter/src/widgets/framework.dart:4700:16) I/flutter (
8598): #98 StatefulElement.performRebuild
(package:flutter/src/widgets/framework.dart:4847:11) I/flutter (
8598): #99 Element.rebuild
(package:flutter/src/widgets/framework.dart:4369:5) I/flutter ( 8598):
#100 StatefulElement.update (package:flutter/src/widgets/framework.dart:4879:5) I/flutter ( 8598):
#101 Element.updateChild (package:flutter/src/widgets/framework.dart:3367:15) I/flutter (
8598): #102 SingleChildRenderObjectElement.update
(package:flutter/src/widgets/framework.dart:6171:14) I/flutter (
8598): #103 Element.updateChild
(package:flutter/src/widgets/framework.dart:3367:15) I/flutter (
8598): #104 ComponentElement.performRebuild
(package:flutter/src/widgets/framework.dart:4700:16) I/flutter (
8598): #105 Element.rebuild
(package:flutter/src/widgets/framework.dart:4369:5) I/flutter ( 8598):
#106 StatelessElement.update (package:flutter/src/widgets/framework.dart:4756:5) I/flutter ( 8598):
#107 Element.updateChild (package:flutter/src/widgets/framework.dart:3367:15) I/flutter (
8598): #108 SingleChildRenderObjectElement.update
(package:flutter/src/widgets/framework.dart:6171:14) I/flutter (
8598): #109 Element.updateChild
(package:flutter/src/widgets/framework.dart:3367:15) I/flutter (
8598): #110 ComponentElement.performRebuild
(package:flutter/src/widgets/framework.dart:4700:16) I/flutter (
8598): #111 StatefulElement.performRebuild
(package:flutter/src/widgets/framework.dart:4847:11) I/flutter (
8598): #112 Element.rebuild
(package:flutter/src/widgets/framework.dart:4369:5) I/flutter ( 8598):
#113 StatefulElement.update (package:flutter/src/widgets/framework.dart:4879:5) I/flutter ( 8598):
#114 Element.updateChild (package:flutter/src/widgets/framework.dart:3367:15) I/flutter (
8598): #115 ComponentElement.performRebuild
(package:flutter/src/widgets/framework.dart:4700:16) I/flutter (
8598): #116 StatefulElement.performRebuild
(package:flutter/src/widgets/framework.dart:4847:11) I/flutter (
8598): #117 Element.rebuild
(package:flutter/src/widgets/framework.dart:4369:5) I/flutter ( 8598):
#118 StatefulElement.update (package:flutter/src/widgets/framework.dart:4879:5) I/flutter ( 8598):
#119 Element.updateChild (package:flutter/src/widgets/framework.dart:3367:15) I/flutter (
8598): #120 ComponentElement.performRebuild
(package:flutter/src/widgets/framework.dart:4700:16) I/flutter (
8598): #121 Element.rebuild
(package:flutter/src/widgets/framework.dart:4369:5) I/flutter ( 8598):
#122 ProxyElement.update (package:flutter/src/widgets/framework.dart:5033:5) I/flutter ( 8598):
#123 Element.updateChild (package:flutter/src/widgets/framework.dart:3367:15) I/flutter (
8598): #124 ComponentElement.performRebuild
(package:flutter/src/widgets/framework.dart:4700:16) I/flutter (
8598): #125 Element.rebuild
(package:flutter/src/widgets/framework.dart:4369:5) I/flutter ( 8598):
#126 ProxyElement.update (package:flutter/src/widgets/framework.dart:5033:5) I/flutter ( 8598):
#127 Element.updateChild (package:flutter/src/widgets/framework.dart:3367:15) I/flutter (
8598): #128 ComponentElement.performRebuild
(package:flutter/src/widgets/framework.dart:4700:16) I/flutter (
8598): #129 StatefulElement.performRebuild
(package:flutter/src/widgets/framework.dart:4847:11) I/flutter (
8598): #130 Element.rebuild
(package:flutter/src/widgets/framework.dart:4369:5) I/flutter ( 8598):
#131 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2777:33) I/flutter (
8598): #132 WidgetsBinding.drawFrame
(package:flutter/src/widgets/binding.dart:894:21) I/flutter ( 8598):
#133 RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:320:5) I/flutter ( 8598):
#134 SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1117:15) I/flutter (
8598): #135 SchedulerBinding.handleDrawFrame
(package:flutter/src/scheduler/binding.dart:1055:9) I/flutter ( 8598):
#136 SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:971:5) I/flutter ( 8598):
#140 _invoke (dart:ui/hooks.dart:157:10) I/flutter ( 8598): #141 PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:256:5)
I/flutter ( 8598): #142 _drawFrame (dart:ui/hooks.dart:120:31)
I/flutter ( 8598): (elided 3 frames from dart:async) I/flutter (
8598): I/flutter ( 8598):
答案 0 :(得分：0)
如果您使用的是 Firebase 等外部服务，则用户可以保持 null 直到完全加载。您应该检查用户的状态并显示加载指示器等，直到它不为空。 Nitesh 在您帖子的评论中也部分提到了这一点。
另见类似帖子：The getter 'displayName' was called on null. - Flutter