Dart Flutter：如何同步使用 SharedPreferences

我在我的Ffltter应用程序中使用共享首选项，我想做的是在启动时将SharedPreferences存储为一个字段，然后在应用程序中同步使用它.然而，我不确定我是否没有错过任何东西. 我想要实现的不是:

method1() async {
  SharedPreferences sp = await SharedPreferences.getInstance();
  return sp.getString('someKey');
}

至

SharedPreferences sp;
//I would probably pass SharedPreferences in construc至r, but the idea is the same
someInitMethod() async {
  sp = await SharedPreferences.getInstance();
}
method1() {
  return sp.getString('someKey');
}
method2() {
  return sp.getString('someKey2');
}
method3() {
  return sp.getString('someKey3');
}

In that way I would achieve synchronous access 至 sharedPrefs. Is it bad solution?

EDIT:
What is worth mentioning is that getInstance method will only check for instance and if there is any than it returns it, so as I see it, is that async is only needed 至 initialize instance. And both set and get methods are sync anyway.

static Future<SharedPreferences> getInstance() async {
  if (_instance == null) {
    final Map<String, Object> fromSystem =
        await _kChannel.invokeMethod('getAll');
    assert(fromSystem != null);
    // Strip the flutter. prefix from the returned preferences.
    final Map<String, Object> preferencesMap = <String, Object>{};
    for (String key in fromSystem.keys) {
      assert(key.startsWith(_prefix));
      preferencesMap[key.substring(_prefix.length)] = fromSystem[key];
    }
    _instance = new SharedPreferences._(preferencesMap);
  }
  return _instance;
}