问题描述
下面的表单使用 Flutter_riverpod 包中的 ConsumerWidget 来监视 firebase 流提供程序中名字/姓氏字段的更新。然后使用 TextEditingControllers 我在字段中设置 watch
ed 文本值,并在更新 Firebase 帐户时获取文本值。
这一切都很好,直到我直接在 Firebase 中更改名字或姓氏字段中的值,这会导致 ui 中的重建。虽然 UI 确实显示更新 Firebase 值,但我在运行日志中收到以下异常。
似乎 riverpod 正在与 TextEditingControllers 对抗状态,这是有道理的,但我该如何克服这个问题?
======== 基础库捕获异常 ================================== ================== 为 TextEditingController 分派通知时抛出以下断言: 在构建期间调用 setState() 或 markNeedsBuild()。
无法将此表单小部件标记为需要构建,因为框架已在构建小部件的过程中。仅当其祖先之一当前正在构建时,才可以将小部件标记为需要在构建阶段构建。允许此异常是因为框架在子级之前构建父级小部件,这意味着将始终构建脏后代。否则,框架可能不会在此构建阶段访问此小部件。 调用 setState() 或 markNeedsBuild() 的小部件是:Form-[LabeledGlobalKey#78eaf] 状态:FormState#7d070 进行违规调用时当前正在构建的小部件是:FirstLastName 肮脏的 依赖项:[UncontrolledProviderScope]
当我使用使用 TextEditingControllers 所需的有状态小部件时,我可以使用 flutter_riverpod 包吗?或者我是否需要考虑使用 hooks_riverpod 包或仅使用 riverpod 包,以便我可以使用 TextEditingControllers 在字段中设置值并从字段中读取值?
代码摘录如下:
account_setup.dart
class AccountSetup extends StatefulWidget {
@override
_AccountSetupState createState() => _AccountSetupState();
}
class _AccountSetupState extends State<AccountSetup> {
final TextEditingController _firstNameController = TextEditingController();
final TextEditingController _lastNameController = TextEditingController();
@override
void initState() {
super.initState();
}
@override
void dispose() {
_firstNameController.dispose();
_lastNameController.dispose();
super.dispose();
}
final _formKey = GlobalKey<FormState>();
@override
Widget build(BuildContext context) {
return SafeArea(
child: Scaffold(
backgroundColor: Colors.white,body: Form(
key: _formKey,child: ListView(
children: [
AccountSettingsTitle(
title: 'Account Setup',),FirstLastName(_firstNameController,_lastNameController),SizedBox(
height: 24.0,],);
}
}
class FirstLastName extends ConsumerWidget {
FirstLastName(
this.firstNameController,this.lastNameController,);
final TextEditingController firstNameController;
final TextEditingController lastNameController;
@override
Widget build(BuildContext context,ScopedReader watch) {
final account = watch(accountStreamProvider);
return account.when(
data: (data) {
firstNameController.text = data.firstName;
lastNameController.text = data.lastName;
return Column(
children: [
Center(
child: Padding(
padding: EdgeInsets.only(top: 10.0,left: 24.0,right: 24.0),child: TextFormField(
controller: firstNameController,decoration: kInputStringFields.copyWith(
hintText: 'First Name',autocorrect: false,validator: (String value) {
if (value.isEmpty) {
return 'Enter first name';
}
return null;
},SizedBox(
height: 14.0,Center(
child: Padding(
padding: EdgeInsets.only(top: 10.0,child: TextFormField(
controller: lastNameController,decoration: kInputStringFields.copyWith(
hintText: 'Last Name',validator: (String value) {
if (value.isEmpty) {
return 'Enter last name';
}
return null;
},);
},loading: () => Container(),error: (_,__) => Container(),);
}
}
top_level_providers.dart
final accountStreamProvider = StreamProvider.autodispose<Account>((ref) {
final database = ref.watch(databaseProvider);
return database != null ? database.accountStream() : const Stream.empty();
});
解决方法
在发送通知时抛出断言 TextEditingController: setState() 或 markNeedsBuild() 期间调用 构建。
当您在构建方法中更新 CahngeNotifier 时会显示此错误,在这种情况下,当您构建小部件时 TextEditingController 会更新:
firstNameController.text = data.firstName;
lastNameController.text = data.lastName;
....
正如您所提到的,hooks_riverpod
可能是一种选择,但如果您不想在完全了解 riverpod 或状态管理之前让自己淹没在库中,我会推荐两种方法:
尝试使用 ProviderListener
(flutter_riverpod 的一部分):
class AccountSetup extends StatefulWidget {
@override
_AccountSetupState createState() => _AccountSetupState();
}
class _AccountSetupState extends State<AccountSetup> {
final TextEditingController _firstNameController = TextEditingController();
final TextEditingController _lastNameController = TextEditingController();
@override
void initState() {
super.initState();
}
@override
void dispose() {
_firstNameController.dispose();
_lastNameController.dispose();
super.dispose();
}
final _formKey = GlobalKey<FormState>();
@override
Widget build(BuildContext context) {
return SafeArea(
child: Scaffold(
backgroundColor: Colors.white,body: Form(
key: _formKey,child: ListView(
children: [
AccountSettingsTitle(
title: 'Account Setup',),ProviderListener<AsyncValue>(
provider: accountStreamProvider,onChange: (context,account) { //This will called when accountStreamProvider updates and a frame after the widget rebuilt
if(account is AsyncData) {
firstNameController.text = data.firstName;
lastNameController.text = data.lastName;
}
},child: FirstLastName(_firstNameController,_lastNameController),SizedBox(
height: 24.0,],);
}
}
或者你可以在 FirstLastName
中使用它并包装小部件结果,它应该工作相同(记住删除 firstNameController.text = data.firstName;
中的行 lastNameController.text = data.lastName;
和 when.data
以防止错误)
@override
Widget build(BuildContext context,ScopedReader watch) {
final account = watch(accountStreamProvider);
return ProviderListener<AsyncValue>(
provider: accountStreamProvider,account) { //This will called when accountStreamProvider updates and a frame after the widget rebuilt
if(account is AsyncData) {
firstNameController.text = data.firstName;
lastNameController.text = data.lastName;
}
},child: account.maybeWhen(
data: (data) {
/// don't call firstNameController.text = data.firstName here
return Column(
children: [
....
],);
},orElse: () => Container(),);
}
}
另一种选择是使用 riverpod 创建您自己的 TextEditingController
并在创建时使用流的数据更新它:
final firstNameProvider = ChangeNotifierProvider.autoDispose<TextEditingController>((ref) {
final account = ref.watch(accountStreamProvider);
final String name = account.maybeWhen(
data: (data) => data?.firstName,orElse: () => null,);
return TextEditingController(text: name);
});
final lastNameProvider = ChangeNotifierProvider.autoDispose<TextEditingController>((ref) {
final account = ref.watch(accountStreamProvider);
final String lastName = account.maybeWhen(
data: (data) => data?.lastName,);
return TextEditingController(text: lastName);
});
然后,而不是在父 StatefulWidget 中创建它们,只需从 FirstLastName();
中的使用者调用它(不再需要在构造函数中传递 TextEditingControllers)
class FirstLastName extends ConsumerWidget {
const FirstLastName({Key key}) : super(key: key);
@override
Widget build(BuildContext context,ScopedReader watch) {
final account = watch(accountStreamProvider);
return account.maybeWhen(
data: (data) {
return Column(
children: [
Center(
child: Padding(
padding: EdgeInsets.only(top: 10.0,left: 24.0,right: 24.0),child: Consumer(
builder: (context,watch,child) {
final firstNameController = watch(firstNameProvider); //call it here
return TextFormField(
controller: firstNameController,decoration: kInputStringFields.copyWith(
hintText: 'First Name',autocorrect: false,validator: (String value) {
if (value.isEmpty) {
return 'Enter first name';
}
return null;
},);
}
),SizedBox(
height: 14.0,Center(
child: Padding(
padding: EdgeInsets.only(top: 10.0,child: child: Consumer(
builder: (context,child) {
final lastNameController = watch(lastNameProvider); //call it here
return TextFormField(
controller: lastNameController,decoration: kInputStringFields.copyWith(
hintText: 'LAst Name',);
},);
}
}
,
问题是您在使用以下行的构建方法执行期间触发了小部件的重建:
firstNameController.text = data.firstName;
lastNameController.text = data.lastName;
但是,解决方案非常简单。只需用零延迟 Future 包装它:
Future.delayed(Duration.zero,(){
firstNameController.text = data.firstName;
lastNameController.text = data.lastName;
});
基本上,每次看到这个错误时,都需要找到构建时触发rebuild的代码,并在Future中进行包装