如何用SharedPreferences保存两个变量？

Question

我试着建立一个应用程序，它应该用以下方法保存两个变量 sharedPreferences 不写 sharedPreferences 代码两遍。于是我写了下面的代码，并使用变量 nameKey 作为保存值的位置，我使用了 safeVariable 的值。我有两个不同的变量应该被保存。counter1 (按下按钮时数值+1)和 counter2 (按下按钮时的值-1)。我遇到的问题是，两个变量都变小了1，但只有一个变量 counter2 应该这样做。谁能找到我代码中的错误？

class _MyHomePageState extends State<MyHomePage> {
  int counter1 = 0;
  int counter2 = 20;
  String nameKey = "eins";
  int safeVariable;

  void _incrementCounter() {
    setState(
      () {
        counter1++;
        counter2--;

        nameKey = "eins";
        safeVariable = counter1;
        save();

        nameKey = "zwei";
        safeVariable = counter2;
        save();
      },
    );
  }

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

  Future<bool> save() async {
    SharedPreferences preferences = await SharedPreferences.getInstance();
    return await preferences.setInt(nameKey, safeVariable);
  }

  Future<int> load() async {
    SharedPreferences preferences = await SharedPreferences.getInstance();
    return preferences.getInt(nameKey);
  }

  set() {
    load().then((value) {
      setState(() {
        safeVariable = value;
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    nameKey = "eins";
    set();
    counter1 = safeVariable;

    nameKey = "zwei";
    set();
    counter2 = safeVariable;

    return Scaffold(
      appBar: AppBar(
        title: Text("Test"),
      ),
      body: Center(
        child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Text(
                'You have pushed the button this many times:',
              ),
              Text(counter1.toString(),
                  style: Theme.of(context).textTheme.headline4),
              Text(counter2.toString(),
                  style: Theme.of(context).textTheme.headline4),
              FloatingActionButton(
                onPressed: _incrementCounter,
                child: Icon(Icons.add),
              ),
            ]),
      ),
    );
  }
}

Answer 1

你必须等到save()操作结束，像这样：In:

void _incrementCounter() {
    setState(
      () {
        counter1++;
        counter2--;

        nameKey = "eins";
        safeVariable = counter1;
        save();

        nameKey = "zwei";
        safeVariable = counter2;
        save();
      },
    );
  }

把 "等待"。

await save();

如果你想在SharedPreferences中一次存储多个值，你只能加载保存一个字符串列表（List）.这是如何做到的。

prefs.setStringList("key", ["a","b","c"]);

如果你有int，你需要把每个int转换成字符串。

List<String> mylist = ["$counter1","$counter2"];