我试图在应用程序加载时加载保存在 sharedPreferences 中的值。但它总是给我第一次构建时声明的 double [0,0,0,0,0,0] 的静态列表。每当我触摸设置状态的东西时，它都会更改为我的正确值。我什至不需要我只是声明它的静态列表，因为 Dart 在问我。如果那里没有保存任何内容，我想要默认列表，否则我想要 sharedpreferences 保存的列表。这是我的代码。

@override initState()  {
    super.initState();
    callLoad();
  }

  callLoad() async{
    List<double> list = await loadTimers();
    setState((){
      timersList = list;
    });
  }

  Future<List<double>> loadTimers() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    List<String> myList =  prefs.getStringList('TimerList');
    List<double> defaultTimersList = [30.0, 60.0, 90.0, 120.0, 150.0, 180.0];
    List<double> savedTimerList;
      if (myList == null ){
        return defaultTimersList;
      } else{
        savedTimerList = myList.map((i)=> double.parse(i)).toList();
        return savedTimerList;
      }
  }

  static List<double> timersList = [0,0,0,0,0,0];

  double timeRemaining1 = timersList[0];
  double timeRemaining2 = timersList[1];
  double timeRemaining3 = timersList[2];
  double timeRemaining4 = timersList[3];
  double timeRemaining5 = timersList[4];
  double timeRemaining6 = timersList[5];

我也试过这种方法，但还是一样。

@override initState()  {
    super.initState();
    loadTimers();
  }


  loadTimers() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    List<String> myList =  prefs.getStringList('TimerList');
    List<double> defaultTimersList = [30.0, 60.0, 90.0, 120.0, 150.0, 180.0];
    List<double> savedTimerList;
      if (myList == null ){
        setState(() {
          timersList = defaultTimersList;

        });
      } else{
        savedTimerList = myList.map((i)=> double.parse(i)).toList();
         setState(() {
           timersList = savedTimerList;
         });
      }
  }

  static List<double> timersList = [0,0,0,0,0,0];

  double timeRemaining1 = timersList[0];
  double timeRemaining2 = timersList[1];
  double timeRemaining3 = timersList[2];
  double timeRemaining4 = timersList[3];
  double timeRemaining5 = timersList[4];
  double timeRemaining6 = timersList[5];

谢谢

用显示问题的小应用程序进行编辑。

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

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo chokuns page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  @override initState()  {
    super.initState();
    callLoad();
  }

  callLoad() async{
    List<double> list = await loadTimers();
    setState((){
      timersList = list;
    });
  }

  Future<List<double>> loadTimers() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    List<String> myList =  prefs.getStringList('TimerList');
    List<double> defaultTimersList = [30.0, 60.0, 90.0, 120.0, 150.0, 180.0];
    List<double> savedTimerList;
    if (myList == null ){
      return defaultTimersList;
    } else{
      savedTimerList = myList.map((i)=> double.parse(i)).toList();
      return savedTimerList;
    }
  }

  static List<double> timersList = [0,0,0,0,0,0];

  double timeRemaining1 = timersList[0];
  double timeRemaining2 = timersList[1];
  double timeRemaining3 = timersList[2];
  double timeRemaining4 = timersList[3];
  double timeRemaining5 = timersList[4];
  double timeRemaining6 = timersList[5];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button \nthis many times:',
              textAlign: TextAlign.center,
            ),
            Text(
              '$timeRemaining1', //showing here $timersList it shows correct values
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
    );
  }
}

最佳答案

将 callLoad 更改为:

  callLoad() async{
    List<double> list = await loadTimers();
    setState((){
      timersList = list;
      timeRemaining1 = timersList[0];
      timeRemaining2 = timersList[1];
      timeRemaining3 = timersList[2];
      timeRemaining4 = timersList[3];
      timeRemaining5 = timersList[4];
      timeRemaining6 = timersList[5];
    });
  }

关于dart - flutter sharedpreferences 未从首次构建开始设置状态，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/56230436/