共享首選項不獲取/保存可變資料

我正在嘗試使用共享首選項保存變數值，并在每次啟動應用程式時檢索它。基本上，我正在嘗試將身份驗證邏輯硬編碼到應用程式中。如果用戶知道密碼，應用程式將回傳正確的字串。此外，如果密鑰正確，圖示也會發生變化。當用戶重新打開應用程式時，應用程式應該記住用戶是否輸入了正確的密鑰。

import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';

var authIcon = const Icon(Icons.lock, color: Colors.redAccent,);
late String enteredPassKEY;

void main() {
  runApp(MaterialApp(
    debugShowCheckedModeBanner: false,
    title: 'Organizer',
    initialRoute: '/home',
    routes: {
      '/home': (context) => const MyHomePage(),
    }
  ));
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key}) : super(key: key);

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

  @override
  void initState() {
    super.initState();
    _getVarSharedPref();
  }

  @override
  Widget build(BuildContext context) { 
  ....
  MaterialButton(onPressed: () { checkPassKey(); },),
  .... 
  }

Future<void> _setPassKEYSharedPref() async{
    final prefs= await SharedPreferences.getInstance();
    await prefs.setString('passKEY', 'enteredPassKEY');
  }

Future<void> _getVarSharedPref() async {
    final prefs= await SharedPreferences.getInstance();
    setState((){
      enteredPassKEY = prefs.getString('passKEY') ?? 'Not_yet_authorised';
      if(enteredPassKEY=='ThisIsPassword') {
        setState(() {
          authIcon = const Icon(Icons.check_circle_sharp, color: Colors.greenAccent,);
        });
      }
    });
  }

  void checkPassKey(){
    if(enteredPassKEY=='ThisIsPassword'){
      setState(() {
        authIcon= const Icon(Icons.check_circle_sharp, color: Colors.greenAccent,);
      });
      _setPassKEYSharedPref();
    }
  }
}

uj5u.com熱心網友回復：

我試圖從你的代碼中構建一個應用程式。這應該會給你一些提示。但在共享首選項中存盤密碼時要小心，因為共享首選項的值并未加密存盤在設備上。

查看軟體包之類的解決方案flutter_secure_storage： https ://pub.dev/packages/flutter_secure_storage

我目前的猜測是你setState()沒有作業，因為目標變數是在有狀態小部件之外宣告的。

import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';

void main() {
  runApp(
    MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Organizer',
      initialRoute: '/home',
      routes: {
        '/home': (context) => const MyHomePage(),
      },
    ),
  );
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key}) : super(key: key);

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final TextEditingController _textInputController = TextEditingController();
  bool authenticated = false;

  @override
  void initState() {
    super.initState();
    _getVarSharedPref();
  }

  @override
  void dispose() {
    _textInputController.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: SizedBox(
          height: 300,
          child: Column(
            children: [
              TextField(
                controller: _textInputController,
                decoration: InputDecoration(prefixIcon: _getAuthIcon()),
              ),
              ElevatedButton(
                onPressed: checkPassKey,
                child: const Text('sign in'),
              ),
            ],
          ),
        ),
      ),
    );
  }

  Future<void> _setPassKEYSharedPref() async {
    final prefs = await SharedPreferences.getInstance();
    // It doesn't make much sense imho, better use a boolean
    await prefs.setString('passKEY', 'ThisIsPassword');
  }

  Future<void> _getVarSharedPref() async {
    final prefs = await SharedPreferences.getInstance();
    final storedPasskey = prefs.getString('passKEY') ?? 'Not_yet_authorised';
    setState(() {
      authenticated = storedPasskey == 'ThisIsPassword';
    });
  }

  void checkPassKey() {
    final String enteredPassKey = _textInputController.text;
    if (enteredPassKey == 'ThisIsPassword') {
      setState(() {
        authenticated = true;
      });
      _setPassKEYSharedPref();
    }
  }

  Icon _getAuthIcon() {
    return authenticated
        ? const Icon(Icons.check_circle_sharp, color: Colors.greenAccent)
        : const Icon(Icons.lock, color: Colors.redAccent);
  }
}

標籤：安卓 扑 镖

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