我正在尝试让用户登录，但是我的代码仅在应用程序热重启后才有效

问题描述

我正在练习一个登录页面，几乎所有内容都已完成。现在，在后台清除应用程序后，使用户保持登录状态的原因是什么。我曾在Flutter中尝试过sharedPreference，这有效。但是它仅在hotRestart而不在重启时才起作用。有人可以帮我吗？

这是sharedPreference类

import 'package:shared_preferences/shared_preferences.dart';

class HelperFunction {
  static String sharedPreferenceUserLoggedInKey = 'userLoggedIn';
  static String sharedPreferenceUserLoggedOutKey = 'userLoggedOut';
  static String sharedPreferenceUserSignedUpKey = 'userSignedUp';

  //saving data to sharedPreference
  static Future<bool> saveUserLoggedInSharedPreference(
      bool isUserLoggedIn) async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    return await prefs.setBool(sharedPreferenceUserLoggedInKey,isUserLoggedIn);
  }

  static Future<bool> saveUserSignedUpSharedPreference(
      bool isUserSignUp) async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    return await prefs.setBool(sharedPreferenceUserSignedUpKey,isUserSignUp);
  }

  static Future<bool> saveUserLoggedOutSharedPreference(
      bool isUserLoggedOut) async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    return await prefs.setBool(
        sharedPreferenceUserLoggedOutKey,isUserLoggedOut);
  }


  //getting data to sharedPreference
  static Future<bool> getUserLoggedInSharedPreference() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    return await prefs.getBool(sharedPreferenceUserLoggedInKey);
  }

  static Future<bool> getUserLoggedOutSharedPreference() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    return await prefs.getBool(sharedPreferenceUserLoggedOutKey);
  }

  static Future<bool> getUserSignedUpSharedPreference() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    return await prefs.getBool(sharedPreferenceUserSignedUpKey);
  }
}

按下按钮上的登录按钮

FlatButton(
onpressed:(){
HelperFunction.saveUserLoggedInSharedPreference(true);
        HelperFunction.saveUserSignedUpSharedPreference(false);
        HelperFunction.saveUserLoggedOutSharedPreference(false);
        Navigator.pushReplacement(
          context,MaterialPageRoute(
            builder: (context) => DashBoard(),),);
  
}
),

注册按钮onpressed功能：

FlatButton(
onpressed:(){
 HelperFunction.saveUserLoggedInSharedPreference(false);
          HelperFunction.saveUserSignedUpSharedPreference(true);
          HelperFunction.saveUserLoggedOutSharedPreference(false);
          Navigator.pop(context);
        }
}
)

已按下功能上的退出按钮：

FlatButton(
onpressed:(){

         HelperFunction.saveUserLoggedOutSharedPreference(true);
         HelperFunction.saveUserLoggedInSharedPreference(false);
         HelperFunction.saveUserSignedUpSharedPreference(false);
         Navigator.pop(context);
        }
}
)

这是我的主要功能

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  SystemChrome.setsystemUIOverlayStyle(systemUIOverlayStyle.light
      .copyWith(systemNavigationBarColor: Colors.black));

  runApp(
    DevicePreview(
      enabled: kReleaseMode,builder: (context) => FlashChat(),);
}

class FlashChat extends StatefulWidget {
  @override
  _FlashChatState createState() => _FlashChatState();
}

class _FlashChatState extends State<FlashChat> {
  bool isUserLoggedIn;
  bool isUserSignedUp;
  bool isUserLoggedOut;

  void getLoggedInStatus() async {
    await HelperFunction.getUserLoggedInSharedPreference().then((value) {
      isUserLoggedIn = value;
      print('isUserLoggedIn = $isUserLoggedIn');
    });
  }

  void getSignedUpStatus() async {
    await HelperFunction.getUserSignedUpSharedPreference().then((value) {
      isUserSignedUp = value;
      print('isUserSignedUp = $isUserSignedUp');
    });
  }

  void getLoggedOutStatus() async {
    await HelperFunction.getUserLoggedOutSharedPreference().then((value) {
      isUserLoggedOut = value;
      print('isUserLoggedOut = $isUserLoggedOut');
    });
  }

  @override
  void initState() {
    getLoggedInStatus();
    getSignedUpStatus();
    getLoggedOutStatus();
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return LayoutBuilder(builder: (context,constraints) {
      return OrientationBuilder(builder: (context,orientation) {
        SizeConfig().init(constraints,orientation);
        return MaterialApp(
          home: isUserLoggedIn == true
              ? DashBoard()
              : isUserSignedUp == true
                  ? LoginScreen()
                  : isUserLoggedOut == true ? LoginScreen() : WelcomeScreen(),debugShowCheckedModeBanner: false,);
      });
    });
  }
}

解决方法

搜索了很长时间后，我找到了答案。通过将值放在setState中，我解决了我的问题。

import 'package:firebase_core/firebase_core.dart';
import 'package:flash/helper/helper_function.dart';
import 'package:flash/screens/dash_board_screen.dart';
import 'package:flash/screens/forgot_password_screen.dart';
import 'package:flash/screens/welcome_screen.dart';
import 'package:flash/size_configuration.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:flash/screens/login_screen.dart';
import 'package:flash/screens/registration_screen.dart';
import 'package:flash/screens/chat_screen.dart';
import 'package:device_preview/device_preview.dart';
import 'package:flutter/services.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  SystemChrome.setSystemUIOverlayStyle(SystemUiOverlayStyle.light
      .copyWith(systemNavigationBarColor: Colors.black));

  runApp(
    DevicePreview(
      enabled: kReleaseMode,builder: (context) => FlashChat(),),);
}

class FlashChat extends StatefulWidget {
  @override
  _FlashChatState createState() => _FlashChatState();
}

class _FlashChatState extends State<FlashChat> {
  bool isUserLoggedIn;
  bool isUserSignedUp;
  bool isUserLoggedOut;

  @override
  void initState() {
    getLoggedInStatus();
    getSignedUpStatus();
    getLoggedOutStatus();
    super.initState();
  }

  void getLoggedInStatus() async {
    await HelperFunction.getUserLoggedInSharedPreference().then((value) {
      setState(() {
        isUserLoggedIn = value;
      });
      print('isUserLoggedIn = $isUserLoggedIn');
    });
  }

  void getSignedUpStatus() async {
    await HelperFunction.getUserSignedUpSharedPreference().then((value) {
      setState(() {
        isUserSignedUp = value;
      });
      print('isUserSignedUp = $isUserSignedUp');
    });
  }

  void getLoggedOutStatus() async {
    await HelperFunction.getUserLoggedOutSharedPreference().then((value) {
      setState(() {
        isUserLoggedOut = value;
      });
      print('isUserLoggedOut = $isUserLoggedOut');
    });
  }

  @override
  Widget build(BuildContext context) {
    return LayoutBuilder(builder: (context,constraints) {
      return OrientationBuilder(builder: (context,orientation) {
        SizeConfig().init(constraints,orientation);
        return MaterialApp(
          home: isUserLoggedIn == true
              ? DashBoard()
              : isUserSignedUp == true || isUserLoggedOut == true
                  ? LoginScreen()
                  : WelcomeScreen(),debugShowCheckedModeBanner: false,);
      });
    });
  }
}