[英]Error: Could not find the correct Provider< > above this Widget
我看不出我在下面做錯了什么,但它拋出了一些提供者錯誤和 buildcontext: 發生這種情況是因為您使用的BuildContext
不包括您選擇的提供者。 有幾個常見的場景:
您在main.dart
中添加了一個新的提供程序並執行了熱重載。 要修復,請執行熱重啟。
您嘗試閱讀的提供者在不同的路線上。
提供者是“范圍內的”。 因此,如果您在路由中插入提供者,則其他路由將無法訪問該提供者。
您使用的BuildContext
是您嘗試讀取的提供者的祖先。
確保 SubscriptionsPage 在您的 MultiProvider/Provider 下。 這通常發生在您創建提供者並嘗試立即讀取它時。
例如,而不是:
Widget build(BuildContext context) { return Provider<Example>( create: (_) => Example(), // Will throw a ProviderNotFoundError, because `context` is associated // to the widget that is the parent of `Provider<Example>` child: Text(context.watch<Example>()), ), }
考慮像這樣使用builder
:
Widget build(BuildContext context) { return Provider<Example>( create: (_) => Example(), // we use `builder` to obtain a new `BuildContext` that has access to the provider builder: (context) { // No longer throws return Text(context.watch<Example>()), } ), }
class RevenueCatProvider extends ChangeNotifier{
RevenueCatProvider() {
init();
}
Entitlement _entitlement = Entitlement.free;
Entitlement get entitlement => _entitlement;
Future init() async {
Purchases.addPurchaserInfoUpdateListener((purchaserInfo) async {
updatePurchasesStatus();
});
}
Future updatePurchasesStatus() async {
final purchaserInfo = await Purchases.getPurchaserInfo();
final entitlements = purchaserInfo.entitlements.active.values.toList();
_entitlement = entitlements.isEmpty ? Entitlement.free : Entitlement.pro;
notifyListeners();
}
}
class SubscriptionsPage extends StatefulWidget {
const SubscriptionsPage({Key? key}) : super(key: key);
@override
State<SubscriptionsPage> createState() => _SubscriptionsPageState();
}
class _SubscriptionsPageState extends State<SubscriptionsPage> {
bool isLoading = false;
@override
Widget build(BuildContext context) {
final entitlement = Provider.of<RevenueCatProvider>(context).entitlement;
return Scaffold(
appBar: AppBar(
title: const Text('Subscription Page'),
),
body: Container(
alignment: Alignment.center,
padding: const EdgeInsets.all(32),
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
buildEntitlement(entitlement),
const SizedBox(height: 32),
Padding(
padding: const EdgeInsets.only(left: 20.0, right: 20),
child: ElevatedButton(
style: ElevatedButton.styleFrom(
minimumSize: const Size.fromHeight(50),
),
child: const Text(
'See Available Plans',
style: TextStyle(fontSize: 20),
),
onPressed: () => isLoading ? null : fetchOffers,
),
),
const SizedBox(height: 32),
SizedBox(
height: 200,
child: Image.asset('images/logo_transparent.png'),
),
],
),
),
);
}
Widget buildEntitlement(Entitlement entitlement) {
switch (entitlement) {
case Entitlement.pro:
return Column(
mainAxisAlignment: MainAxisAlignment.end,
crossAxisAlignment: CrossAxisAlignment.center,
children: const [
SizedBox(height: 40),
Text('You are on a Paid plan',
style: TextStyle(
fontSize: 20,
),
),
SizedBox(height: 10),
Icon(Icons.paid,
size: 100,
),
],
);
case Entitlement.free:
default:
return Column(
mainAxisAlignment: MainAxisAlignment.end,
crossAxisAlignment: CrossAxisAlignment.center,
children: const [
SizedBox(height: 40),
Text('You are on a Free plan',
style: TextStyle(
fontSize: 20,
),
),
SizedBox(height: 10),
Icon(Icons.lock,
size: 100,
),
],
);
}
}
Future fetchOffers() async {
final offerings = await PurchaseApi.fetchOffers();
if (offerings.isEmpty) {
ScaffoldMessenger.of(context).showSnackBar(const SnackBar(
content: Text('No Subscription'),
));
} else {
final packages = offerings
.map((offer) => offer.availablePackages)
.expand((pair) => pair)
.toList();
showModalBottomSheet(
useRootNavigator: true,
isDismissible: true,
isScrollControlled: true,
backgroundColor: kLightPrimary,
shape: const RoundedRectangleBorder(
borderRadius: BorderRadius.vertical(top: Radius.circular(25.0)),
),
context: context,
builder: (BuildContext context) {
return StatefulBuilder(
builder: (BuildContext context, StateSetter setModalState) {
return PaywallWidget(
packages: packages,
title: '⭐️ Upgrade your plan',
description: 'Upgrade your plan to enjoy unlimited ad-free reviews',
onClickedPackage: (package) async {
await PurchaseApi.purchasePackage(package);
Navigator.pop(context);
},
);
});
},
);
}
}
}
您需要確保在小部件上方的小部件樹中某處有一個ChangeNotifierProvider
,它使用更改通知程序。
例如,當您調用final entitlement = Provider.of<RevenueCatProvider>(context).entitlement;
. 遍歷小部件樹以搜索匹配的ChangeNotifierProvider
。
您收到的錯誤告訴您,沒有。
這樣的事情應該有效。
class Sample extends StatelessWidget {
const Sample({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return ChangeNotifierProvider(
create: (_) => new RevenueCatProvider(),
child: SubscriptionsPage(),
);
}
}
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