StateNotifier未更新Flutter Riverpod中FutureProvider的数据函数内部

Question

带有性别的StateNotifier不会随着下拉选项的更改而更新。我在文件的开头有这些提供商：

class GenderController extends StateNotifier<String>{
GenderController(String state) : super(state);
}
final profileProvider = FutureProvider.autoDispose((ref) {
final details = ref.watch(authToken);
var data = API().staffProfile(token: details['token'], staffID: details['ID']);
return data;
});
final gender = StateNotifierProvider.autoDispose((ref) => GenderController(""));

这就是构建方法在ConsumerWidget中的样子：

Widget build(BuildContext context, WidgetRef ref) {
var dropdownValue = ref.watch(gender);
final details = ref.watch(profileProvider);
return details.when(
data: (data){

dropdownValue = data['gender'];
// show the form with the info
return Padding(
padding: const EdgeInsets.all(8.0),
child: Form(
key: formKey,
child: Column(
children: [
DropdownButton2(
isExpanded: true,
underline: Container(
color: kDarkGrey,
height: 1.0,
),
buttonPadding: const EdgeInsets.symmetric(vertical: 10.0),
hint: const CustomText(
text: "Gender",
fontSize: 16.0,
color: kBlack,
),
items: genders
.map((item) => DropdownMenuItem<String>(
value: item,
child: Text(
item,
style: const TextStyle(
fontSize: 16,
color: kBlack,
),
overflow: TextOverflow.ellipsis,
),
))
.toList(),
value: dropdownValue == "" ? null : dropdownValue.toString(),
onChanged: (value) {
ref.watch(gender.notifier).state =  value!;
}
),
],
)
),
);
},
error: (err, _){
debugPrint(_.toString());
return const Center(
child: CustomText(
text: "Error getting profile",
),
);
},
loading: () => Center(
child: CircularProgressIndicator(
color: kPrimary,
),
)
);
}

我还尝试使dropdownValue的数据类型为final，然后将数据分配为CCD_；"GenderController"的StateNotificationr实例的至少一个侦听器在通知程序尝试更新其状态时引发异常"错误请帮忙。

Answer 1

在回调中，必须调用ref.read

ref.read(gender.notifier).state = data['gender'];

Answer 2

我想明白了。在调用详细信息之前，我初始化了下拉列表。如下所示：

DropdownButton2 dropdown = DropdownButton2(
isExpanded: true,
underline: Container(
color: kDarkGrey,
height: 1.0,
),
buttonPadding: const EdgeInsets.symmetric(vertical: 10.0),
hint: const CustomText(
text: "Gender",
fontSize: 16.0,
color: kBlack,
),
items: genders
.map((item) => DropdownMenuItem<String>(
value: item,
child: Text(
item,
style: const TextStyle(
fontSize: 16,
color: kBlack,
),
overflow: TextOverflow.ellipsis,
),
))
.toList(),
value: dropdownValue == "" ? null : dropdownValue.toString(),
onChanged: (value) {
ref.read(gender.notifier).state =  value!;
}
);

然后，在FutureProvider中返回数据后，我更新了StateNotifier，如下所示：

final profileProvider = FutureProvider.autoDispose((ref) async {
final details = ref.watch(authToken);
var data = await API().staffProfile(token: details['token'], staffID: details['ID']);
ref.read(gender.notifier).state = data['gender'];
return data;
});

现在一切都很好，而且应该如此。