参数类型'void Function()'不能赋值给参数类型'void Function(BuildContext)?

Question

我创建了一个名为

isJoined

的 bool，当我想将它更改为形成

false

到

true

当我点击一个按钮时，但它给出了命名错误。我在共享首选项中存储

isJoined

：

bool isJoined = false;

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

  _loadData() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    setState(() {
      isJoined = prefs.getBool('isJoined') ?? false; //the ?? false is a null checker//
    });
  }
// now I save it//
_savebool() async {
  SharedPreferences prefs = await SharedPreferences.getInstance();
  await prefs.setBool("isJoined", isJoined);
}

但这就是问题发生的地方：

onPressed: () {isJoined = true, _savebool()},
//The argument type 'void Function()' can't be assigned 
//to the parameter type 'void Function(BuildContext)?'

我试过在

?

中添加一个

bool

并在每个

isJoined

之后添加一个空检查器（！），但这不起作用。它给出了同样的错误。

Answer 1

class HomePage extends StatefulWidget {
const HomePage({super.key});

@override
State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
bool isJoined = false;

late SharedPreferences prefs;

@override
void initState() {
super.initState();
SharedPreferences.getInstance().then((value) {
  setState(() {
    prefs = value;
  });
  //load data
  _loadData();
});
}

_loadData() async {
print("isJoined before setState: $isJoined");
bool storedIsJoined = prefs.getBool('isJoined') ?? false;
setState(() {
  isJoined = storedIsJoined; //the ?? false is a null checker//
});
print("isJoined after setState: $isJoined");
}

 // now I save it//
_savebool() async {
print("isJoined saving: $isJoined");
await prefs.setBool("isJoined", isJoined);
}

 @override
 Widget build(BuildContext context) {
return Scaffold(
  body: Column(
    crossAxisAlignment: CrossAxisAlignment.center,
    mainAxisAlignment: MainAxisAlignment.center,
    children: [
      ElevatedButton(
          onPressed: () async {
            await _savebool();
          },
          child: const Text("Go to next page"))
    ],
  ),
);
}
}