请帮助我详细解释我如何修改我的代码。我是Flutter的初学者，现在我正在执行任务，其本质是在登录屏幕中使用Shared Preferenced，并将用户数据保存在FireBase中。当用户第一次输入数据时，他进入了主屏幕，但是当用户退出应用程序并尝试再次登录时，应该是因为他不需要输入密码并再次登录。
How to fix the error with the int, so that Shared Preferensed is finally working.
我的代码
import 'package:flutter/material.dart';
import 'package:logining/home_screen/home_screen.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:google_sign_in/google_sign_in.dart';
import 'package:shared_preferences/shared_preferences.dart';
class LoginScreen extends StatefulWidget {
@override
LoginScreenState createState() {
return new LoginScreenState();
}
}
enum LoginStatus{
notSignIn,
signIn,
}
class LoginScreenState extends State<LoginScreen> {
LoginStatus _loginStatus = LoginStatus.notSignIn;
String _email, _password;
bool _obscureText = true;
final GlobalKey<FormState> _formKey = GlobalKey<FormState>();
final FirebaseAuth _auth = FirebaseAuth.instance;
final GoogleSignIn googleSignIn = GoogleSignIn();
TextEditingController email = new TextEditingController();
TextEditingController password = new TextEditingController();
SharedPreferences sharedPreferences;
Future<FirebaseUser> _signInGoogle() async{
GoogleSignInAccount googleSignInAccount = await googleSignIn.signIn();
GoogleSignInAuthentication gSa =await googleSignInAccount.authentication;
FirebaseUser user = await _auth.signInWithGoogle(
idToken: gSa.idToken,
accessToken: gSa.accessToken
);
print('User Name : ${user.displayName}');
return Navigator.push(context, MaterialPageRoute(builder: (context) => HomeScreen(user: user)));
}
safePref()async{
SharedPreferences preferences = await SharedPreferences.getInstance();
setState((){
preferences.setString('email', _email);
preferences.setString('password', _password);
preferences.commit();
});
}
var value;
getPref()async{
SharedPreferences preferences = await SharedPreferences.getInstance();
setState(() {
value = preferences.getInt("email");
value = preferences.getInt("password");
_loginStatus = value == null ? LoginStatus.notSignIn : LoginStatus.signIn;
});
}
@override
void initState(){
super.initState();
getPref();
}
@override
Widget build(BuildContext context) {
switch(_loginStatus){
case LoginStatus.notSignIn:
return Scaffold(
appBar: AppBar(
title: Text('Login'),
),
resizeToAvoidBottomPadding: false,
body: ListView(children: <Widget>[
Container(
child: Form(
key: _formKey,
autovalidate: true,
child: Column(
children: <Widget>[
SizedBox(
height: 50,
),
Padding(
child: Image.asset(
'images/logo.png',
width: 100.0,
height: 100.0,
),
padding: EdgeInsets.fromLTRB(50, 0, 50, 40),
),
Padding(
padding: EdgeInsets.fromLTRB(25, 0, 50, 10),
child: TextFormField(
controller: email,
validator: (email) {
if (email.isEmpty) {
return 'Provide an Email';
}
},
style: TextStyle(
color: Color(0xFF01579B),
fontSize: 18.0,
),
decoration: InputDecoration(
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(30),
),
hintText: 'Enter your Email',
labelText: "Email",
icon: Padding(
padding: EdgeInsets.only(top: 20.0),
child: Icon(Icons.email),
)),
onSaved: (email) => _email = email,
),
),
Padding(
padding: EdgeInsets.fromLTRB(25, 0, 50, 10),
child: TextFormField(
controller: password,
validator: (password) {
if (password.isEmpty) {
return 'Provide an password';
}
},
obscureText: _obscureText,
style: TextStyle(
color: Color(0xFF01579B),
fontSize: 18.0,
),
decoration: InputDecoration(
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(30),
),
hintText: 'Enter your password',
labelText: "Password",
icon: Padding(
padding: EdgeInsets.only(top: 15.0),
child: Icon(Icons.lock),
),
suffixIcon: GestureDetector(
onTap: () {
setState(() {
_obscureText = !_obscureText;
});
},
child: Icon(
_obscureText
? Icons.visibility
: Icons.visibility_off,
semanticLabel: _obscureText
? 'show password'
: 'hide password',
),
),
),
onSaved: (password) => _password = password,
),
),
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Padding(
padding: EdgeInsets.symmetric(horizontal: 10),
child: RaisedButton(
color: Color(0xFFD50000),
textColor: Color(0xFFFFFFFF),
child: Text('Login with Google'),
onPressed:(){ _signInGoogle().then((FirebaseUser user){
print(user);
}).catchError((onError){
print(onError);
});
}
),
),
Padding(
padding: EdgeInsets.symmetric(horizontal: 10),
child: RaisedButton(
color: Color(0xFF448AFF),
textColor: Color(0xFFFFFFFF),
child: Text('Login'),
onPressed: signIn,
),
),
]),
Padding(
padding:
EdgeInsets.symmetric(horizontal: 10, vertical: 5),
child: FlatButton(
textColor: Color(0xFF448AFF),
child: Text('Forgot Password'),
onPressed: () {
print('onPressed');
},
),
),
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Padding(
padding: EdgeInsets.fromLTRB(50, 70, 0, 10),
child: Text(
'Still do not have an account ',
style: TextStyle(color: Color(0xFF9E9E9E)),
),
),
Padding(
padding: EdgeInsets.fromLTRB(0, 70, 30, 10),
child: FlatButton(
textColor: Color(0xFF448AFF),
child: Text('registration'),
onPressed: () {
Navigator.of(context).pushNamedAndRemoveUntil(
'/registration', (Route<dynamic> route) => false);
},
),
),
],
),
],
),
),
),
]),
);
break;
case LoginStatus.signIn:
return HomeScreen();
break;
}
}
Future<void> signIn() async {
final formState = _formKey.currentState;
if(formState.validate()) {
setState(() {
_loginStatus = LoginStatus.signIn;
formState.save();
});
try {
FirebaseUser user = await FirebaseAuth.instance.signInWithEmailAndPassword(email: _email, password: _password);
}catch(e){
print(e.message);
}
}
}
}