我正在开发适用于 Android 的 Flutter 应用程序，当我添加如果用户存在则刷新页面后无需再次登录时遇到问题。在 flutter 项目中，通过创建文件 CheckUser 但当我从主 dart 调用此文件时，它会给我一个带有文本的红色屏幕的错误 ---- 预期为“Widget”类型的值，但得到了“'”类型的值_Future
在我的项目中实现 checkuser 文件后出现问题，该文件检查用户是否已经拥有帐户。
这是我在项目中使用的文件
检查用户文件
import 'package:firebase/login.dart';
import 'package:firebase/main.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:flutter/material.dart';
class CheckUser extends StatefulWidget {
const CheckUser({super.key});
@override
State<CheckUser> createState() => _CheckUserState();
}
class _CheckUserState extends State<CheckUser> {
@override
Widget build(BuildContext context) {
return checkuser();
}
checkuser()async{
final user = FirebaseAuth.instance.currentUser;
if(user!=null ){
return HomeScreen();
}
else {
return Loginpage();
}
}
}
主飞镖文件
import 'package:firebase/checkuser.dart';
import 'package:firebase/login.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:flutter/material.dart';
void main()async{
WidgetsFlutterBinding.ensureInitialized();
await Firebase.initializeApp(
options: FirebaseOptions(apiKey: "AIzaSyDQZxWx776Vhl7Hw4VG5RhaSPX13v6ygRk",
appId: "1:1049018787351:android:309401ce75103c0f171e52",
messagingSenderId: "1049018787351",
projectId: "harsh-c8ebd")
);
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({super.key});
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
home: CheckUser(),
);
}
}
class HomeScreen extends StatefulWidget {
@override
_HomeScreenState createState() => _HomeScreenState();
}
class _HomeScreenState extends State<HomeScreen> {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Home Screen'),
),
body: Text('hello'),
);
}
}
登录文件
import 'package:firebase/helper.dart';
import 'package:firebase/main.dart';
import 'package:firebase/signuppage.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
class Loginpage extends StatefulWidget {
const Loginpage({Key? key}) : super(key: key);
@override
State<Loginpage> createState() => _LoginpageState();
}
class _LoginpageState extends State<Loginpage> {
TextEditingController emailcontroller = TextEditingController();
TextEditingController passwordcontroller = TextEditingController();
login(String email, String password) async {
if (email == "" && password == "") {
return Helper.CustomAlertBox(context, "Enter required fields");
} else {
try {
UserCredential userCredential = await FirebaseAuth.instance
.signInWithEmailAndPassword(email: email, password: password);
Navigator.push(
context,
MaterialPageRoute(builder: (context) => SignUpPage()),
);
} on FirebaseAuthException catch (ex) {
return Helper.CustomAlertBox(context, ex.code.toString());
}
}
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("Login page"),
centerTitle: true,
),
body: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Helper.CustomTextField(emailcontroller, "Email", Icons.mail, false),
Helper.CustomTextField(
passwordcontroller, "Password", Icons.password, true),
SizedBox(height: 30),
Helper.CustomButton(
() {
login(emailcontroller.text.toString(),
passwordcontroller.text.toString());
},
"Login",
),
SizedBox(height: 20),
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Text("Don't have an account?"),
TextButton(
onPressed: () {
Navigator.push(context,
MaterialPageRoute(builder: (context) => SignUpPage()));
},
child: Text(
"Sign up",
style: TextStyle(fontSize: 20),
),
)
],
)
],
),
);
}
}
注册文件
import 'package:firebase/helper.dart';
import 'package:firebase/main.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
class SignUpPage extends StatefulWidget {
const SignUpPage({Key? key}) : super(key: key);
@override
State<SignUpPage> createState() => _SignUpPageState();
}
class _SignUpPageState extends State<SignUpPage> {
TextEditingController emailcontroller = TextEditingController();
TextEditingController passwordcontroller = TextEditingController();
signUp(String email, String password) async {
if (email == "" && password == "") {
Helper.CustomAlertBox(context, "Enter required fields");
} else {
try {
UserCredential userCredential = await FirebaseAuth.instance
.createUserWithEmailAndPassword(email: email, password: password);
Navigator.push(
context,
MaterialPageRoute(builder: (context) => HomeScreen()),
);
} on FirebaseAuthException catch (ex) {
return Helper.CustomAlertBox(context, ex.code.toString());
}
}
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("Sign Up page"),
centerTitle: true,
),
body: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Helper.CustomTextField(emailcontroller, "Email", Icons.mail, false),
Helper.CustomTextField(passwordcontroller, "Password", Icons.password, true),
SizedBox(height: 20),
Helper.CustomButton(
() {
signUp(emailcontroller.text.toString(), passwordcontroller.text.toString());
},
"Sign Up",
),
],
),
);
}
}
帮助文件
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
class Helper {
static CustomTextField(TextEditingController controller, String text, IconData iconData, bool tohide) {
return Padding(
padding: const EdgeInsets.symmetric(horizontal: 25, vertical: 40),
child: TextField(
controller: controller,
obscureText: tohide,
decoration: InputDecoration(
hintText: text,
suffixIcon: Icon(iconData),
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(25),
),
),
),
);
}
static CustomButton(VoidCallback voidCallback, String text) {
return SizedBox(
height: 50,
width: 300,
child: ElevatedButton(
onPressed: voidCallback,
style: ElevatedButton.styleFrom(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(25),
),
),
child: Text(
text,
style: TextStyle(
color: Colors.red,
fontSize: 20,
),
),
),
);
}
static CustomAlertBox(BuildContext context, String text) {
return showDialog(
context: context,
builder: (BuildContext context) {
return AlertDialog(
title: Text(text),
actions: [
TextButton(
onPressed: () {
Navigator.pop(context);
},
child: Text("OK"),
),
],
);
},
);
}
}
pubsyml 文件
name: firebase
description: "A new Flutter project."
# The following line prevents the package from being accidentally published to
# pub.dev using `flutter pub publish`. This is preferred for private packages.
publish_to: 'none' # Remove this line if you wish to publish to pub.dev
# The following defines the version and build number for your application.
# A version number is three numbers separated by dots, like 1.2.43
# followed by an optional build number separated by a +.
# Both the version and the builder number may be overridden in flutter
# build by specifying --build-name and --build-number, respectively.
# In Android, build-name is used as versionName while build-number used as versionCode.
# Read more about Android versioning at https://developer.android.com/studio/publish/versioning
# In iOS, build-name is used as CFBundleShortVersionString while build-number is used as CFBundleVersion.
# Read more about iOS versioning at
# https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html
# In Windows, build-name is used as the major, minor, and patch parts
# of the product and file versions while build-number is used as the build suffix.
version: 1.0.0+1
environment:
sdk: '>=3.2.4 <4.0.0'
# Dependencies specify other packages that your package needs in order to work.
# To automatically upgrade your package dependencies to the latest versions
# consider running `flutter pub upgrade --major-versions`. Alternatively,
# dependencies can be manually updated by changing the version numbers below to
# the latest version available on pub.dev. To see which dependencies have newer
# versions available, run `flutter pub outdated`.
dependencies:
flutter:
sdk: flutter
# The following adds the Cupertino Icons font to your application.
# Use with the CupertinoIcons class for iOS style icons.
cupertino_icons: ^1.0.2
firebase_core: ^2.27.0
firebase_auth: ^4.17.8
dev_dependencies:
flutter_test:
sdk: flutter
# The "flutter_lints" package below contains a set of recommended lints to
# encourage good coding practices. The lint set provided by the package is
# activated in the `analysis_options.yaml` file located at the root of your
# package. See that file for information about deactivating specific lint
# rules and activating additional ones.
flutter_lints: ^3.0.2
# For information on the generic Dart part of this file, see the
# following page: https://dart.dev/tools/pub/pubspec
# The following section is specific to Flutter packages.
flutter:
# The following line ensures that the Material Icons font is
# included with your application, so that you can use the icons in
# the material Icons class.
uses-material-design: true
# To add assets to your application, add an assets section, like this:
# assets:
# - images/a_dot_burr.jpeg
# - images/a_dot_ham.jpeg
# An image asset can refer to one or more resolution-specific "variants", see
# https://flutter.dev/assets-and-images/#resolution-aware
# For details regarding adding assets from package dependencies, see
# https://flutter.dev/assets-and-images/#from-packages
# To add custom fonts to your application, add a fonts section here,
# in this "flutter" section. Each entry in this list should have a
# "family" key with the font family name, and a "fonts" key with a
# list giving the asset and other descriptors for the font. For
# example:
# fonts:
# - family: Schyler
# fonts:
# - asset: fonts/Schyler-Regular.ttf
# - asset: fonts/Schyler-Italic.ttf
# style: italic
# - family: Trajan Pro
# fonts:
# - asset: fonts/TrajanPro.ttf
# - asset: fonts/TrajanPro_Bold.ttf
# weight: 700
#
# For details regarding fonts from package dependencies,
# see https://flutter.dev/custom-fonts/#from-packages
enter image description here
添加 Widget 以返回 checkuser 函数的类型并删除 async 关键字。
Widget checkuser(){
final user = FirebaseAuth.instance.currentUser;
if(user!=null ){
return HomeScreen();
}
else {
return Loginpage();
}
}