我想知道从 API 获取我需要的所有提供者状态的最佳方法是什么。登录后我不会在主屏幕上执行此操作，因为当我从另一个屏幕导航回来时，总是会调用 initState()。
现在，我的方法是创建一个仅在登录后构建的 LoadScreen 小部件。在那里，我使用 FutureBuilder 加载我需要的状态，然后导航到 Main。这种方法会产生异常，但“有效”。什么是正确的做法？
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:shop/providers/auth.dart';
import 'package:shop/providers/collections.dart';
import 'package:shop/providers/customers.dart';
import 'package:shop/providers/orders.dart';
import 'package:shop/providers/products.dart';
import 'package:shop/providers/recommended_categories.dart';
import 'package:shop/providers/user_data.dart';
import 'package:shop/screens/main_screen.dart';
class LoadScreen extends StatelessWidget {
static const routeName = '/load-screen'; //It shouldn't never be used.
@override
Widget build(BuildContext context) {
Future<bool> loadState() async {
//Loading all state data from firebase
print('Loading States');
try {
final authData =
await Provider.of<Auth>(context, listen: false).authData;
final futures = <Future<dynamic>>[
Provider.of<Products>(context, listen: false)
.fetchAndSet(authData), //Products
Provider.of<RecommendedCategories>(context, listen: false)
.fetchAndSet(authData),
Provider.of<Customers>(context, listen: false).fetchAndSet(authData),
Provider.of<Orders>(context, listen: false).fetchAndSet(authData),
Provider.of<UserData>(context, listen: false).fetchAndSet(authData),
Provider.of<Collections>(context, listen: false)
.fetchAndSet(authData),
];
print('Created futures list');
final results = await Future.wait(futures);
print(results);
} catch (error, stacktrace) {
print(error);
print(stacktrace);
throw error;
}
return true;
}
return Scaffold(
body: FutureBuilder(
future: loadState(),
builder: (context, snapshot) {
if (snapshot.connectionState == ConnectionState.done) {
if (snapshot.hasError) {
return Center(
child: Text('${snapshot.error}'),
);
}
Navigator.of(context).pushNamed(MainScreen.routeName);
return Center(
child: Text('Loading...'),
);
} else {
return Center(
child: Text('Loading...'),
);
}
},
),
);
}
}
我的主要是
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:shop/providers/collections.dart';
import 'package:shop/providers/customers.dart';
import 'package:shop/providers/products.dart';
import 'package:shop/providers/recommended_categories.dart';
import 'package:shop/providers/user_data.dart';
import 'package:shop/screens/add_collection_screen.dart';
import 'package:shop/screens/add_order_screen.dart';
import 'package:shop/screens/load_screen.dart';
import 'package:shop/screens/products_screen.dart';
import 'package:shop/screens/customer_order_screen.dart';
import 'package:shop/screens/edit_customer_screen.dart';
import 'package:shop/screens/main_screen.dart';
//import './screens/products_overview_screen.dart';
import 'screens/cart_screen.dart';
import './screens/product_detail_screen.dart';
import './providers/cart.dart';
import './providers/orders.dart';
import './providers/auth.dart';
import './screens/orders_screen.dart';
import './screens/auth_screen.dart';
import './screens/splash-screen.dart';
import './screens/collections_screen.dart';
// import './screens/collection_products_screen.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
print('MyApp.build');
return MultiProvider(
providers: [
ChangeNotifierProvider(
//Recommended approach when a new object is provided.
create: (ctx) => Auth(),
),
ChangeNotifierProvider<Products>(
//Recommended approach when a new object is provided.
create: (ctx) => Products(),
),
ChangeNotifierProvider(
create: (ctx) => Cart(),
),
ChangeNotifierProvider<Orders>(
create: (ctx) => Orders(),
),
ChangeNotifierProvider(
create: (ctx) => Customers(),
),
ChangeNotifierProvider(
create: (ctx) => RecommendedCategories(),
),
ChangeNotifierProvider(
create: (ctx) => UserData(),
),
ChangeNotifierProvider(
create: (ctx) => Collections(),
),
],
child: Consumer<Auth>(
builder: (ctx, auth, _) => MaterialApp(
title: 'Shop',
theme: ThemeData(
primarySwatch: Colors.deepOrange,
accentColor: Colors.purple,
fontFamily: 'Lato',
),
home: auth.canAuth
? LoadScreen()
: FutureBuilder(
future: auth.tryAutoLogin(),
builder: (ctx, authResultSnapshot) =>
authResultSnapshot.connectionState ==
ConnectionState.waiting
? SplashScreen()
: AuthScreen(),
),
routes: {
ProductDetailScreen.routeName: (ctx) => ProductDetailScreen(),
CartScreen.routeName: (ctx) => CartScreen(),
OrdersScreen.routeName: (ctx) => OrdersScreen(),
CollectionProductsScreen.routeName: (ctx) =>
CollectionProductsScreen(),
CollectionsScreen.routeName: (ctx) => CollectionsScreen(false),
EditCustomerScreen.routeName: (ctx) => EditCustomerScreen(),
CustomerOrderScreen.routeName: (ctx) => CustomerOrderScreen(),
AddOrderScreen.routeName: (ctx) => AddOrderScreen(),
AddCollectionScreen.routeName: (ctx) => AddCollectionScreen(),
LoadScreen.routeName: (ctx) => LoadScreen(),
MainScreen.routeName: (ctx) => MainScreen(),
},
),
),
);
}
}
我遇到以下异常
Exception caught by widgets library ═══════════════════════════════════
The following assertion was thrown building FutureBuilder<bool>(dirty, state: _FutureBuilderState<bool>#547fc):
setState() or markNeedsBuild() called during build.
This Overlay widget cannot be marked as needing to build because the framework is already in the process of building widgets. A widget can be marked as needing to be built during the build phase only if one of its ancestors is currently building. This exception is allowed because the framework builds parent widgets before children, which means a dirty descendant will always be built. Otherwise, the framework might not visit this widget during this build phase.
The widget on which setState() or markNeedsBuild() was called was: Overlay-[LabeledGlobalKey<OverlayState>#68f4a]
state: OverlayState#77296(tickers: tracking 0 tickers, entries: [OverlayEntry#847ca(opaque: true; maintainState: false), OverlayEntry#7a334(opaque: false; maintainState: true), OverlayEntry#9e3e0(opaque: false; maintainState: false), OverlayEntry#99d1e(opaque: false; maintainState: true)])
The widget which was currently being built when the offending call was made was: FutureBuilder<bool>
dirty
state: _FutureBuilderState<bool>#547fc
The relevant error-causing widget was
FutureBuilder<bool>
lib/screens/load_screen.dart:48
When the exception was thrown, this was the stack
#0 Element.markNeedsBuild.<anonymous closure>
package:flutter/…/widgets/framework.dart:4138
#1 Element.markNeedsBuild
package:flutter/…/widgets/framework.dart:4153
#2 State.setState
package:flutter/…/widgets/framework.dart:1287
#3 OverlayState.rearrange
package:flutter/…/widgets/overlay.dart:436
#4 NavigatorState._flushHistoryUpdates
package:flutter/…/widgets/navigator.dart:4043
...
════════════════════════════════════════════════════════════════════════════════
E/flutter ( 5098): [ERROR:flutter/lib/ui/ui_dart_state.cc(186)] Unhandled Exception: 'package:flutter/src/widgets/navigator.dart': Failed assertion: line 2997 pos 18: '!navigator._debugLocked': is not true.
E/flutter ( 5098): #0 _AssertionError._doThrowNew (dart:core-patch/errors_patch.dart:46:39)
E/flutter ( 5098): #1 _AssertionError._throwNew (dart:core-patch/errors_patch.dart:36:5)
E/flutter ( 5098): #2 _RouteEntry.handlePush.<anonymous closure>
package:flutter/…/widgets/navigator.dart:2997
E/flutter ( 5098): #3 TickerFuture.whenCompleteOrCancel.thunk
package:flutter/…/scheduler/ticker.dart:407
E/flutter ( 5098): #4 _rootRunUnary (dart:async/zone.dart:1362:47)
E/flutter ( 5098): #5 _CustomZone.runUnary (dart:async/zone.dart:1265:19)
E/flutter ( 5098): #6 _FutureListener.handleValue (dart:async/future_impl.dart:152:18)
E/flutter ( 5098): #7 Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:704:45)
E/flutter ( 5098): #8 Future._propagateToListeners (dart:async/future_impl.dart:733:32)
E/flutter ( 5098): #9 Future._completeWithValue (dart:async/future_impl.dart:539:5)
E/flutter ( 5098): #10 Future._asyncCompleteWithValue.<anonymous closure> (dart:async/future_impl.dart:577:7)
E/flutter ( 5098): #11 _rootRun (dart:async/zone.dart:1354:13)
E/flutter ( 5098): #12 _CustomZone.run (dart:async/zone.dart:1258:19)
E/flutter ( 5098): #13 _CustomZone.runGuarded (dart:async/zone.dart:1162:7)
E/flutter ( 5098): #14 _CustomZone.bindCallbackGuarded.<anonymous closure> (dart:async/zone.dart:1202:23)
E/flutter ( 5098): #15 _microtaskLoop (dart:async/schedule_microtask.dart:40:21)
E/flutter ( 5098): #16 _startMicrotaskLoop (dart:async/schedule_microtask.dart:49:5)
我建议您从
futurebuilderstreambuilderproviderProvider.of<your_class>(context,listen=false).mymethod
我保持listen=false，因为我没有使用提供程序进行任何广播通知。
查看
streambuilder