MaterialPageRoute<dynamic>：类型'Widget‘不是’Widget‘类型的子类型// Flutter(Null))
MaterialPageRoute<dynamic>：类型'Widget‘不是’Widget‘类型的子类型// Flutter(Null))
提问于 2020-09-11 04:14:38
我正在尝试导航到相机屏幕，当我触发导航时，我收到错误消息
Another exception was thrown: type 'Future<dynamic>' is not a subtype of type 'Widget'
Another exception was thrown: setState() or markNeedsBuild() called during build.该错误指向我所在的上一个页面的导航。
我也在那里看到了这个错误
The AnimationController notifying status listeners was: AnimationController#a911e(⏮ 0.000; paused; for MaterialPageRoute<dynamic>(null))onTap: () => Navigator.push(
context,
MaterialPageRoute(
builder: (context) => CameraScreen())),这是获取错误的函数
captureImageWithCamera() async {
Navigator.pop(this.context);
File imageFile = await ImagePicker.pickImage(
source: ImageSource.camera,
maxHeight: 680,
maxWidth: 970,
);
if (imageFile != null) {
//imageFile = await cropImage(imageFile);
setState(() {
//this.file = imageFile as File;
print(file);
});
await controller.dispose();
}
}为了获得完整的上下文，这里是第一个页面的完整构建器，它调用到相机屏幕的导航。您将在其中看到指向CameraScreen的导航。
createStoryView() {
return FutureBuilder(
future: usersReference.document(currentOnlineUserId).get(),
builder: (context, dataSnapshot) {
if (!dataSnapshot.hasData) {
return circularProgress();
} else {
User user = User.fromDocument(dataSnapshot.data);
return Material(
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Padding(
padding: const EdgeInsets.all(0.0),
child: Card(
color: Colors.white,
elevation: 0.0,
child: Padding(
padding: const EdgeInsets.all(8.0),
child: ListTile(
leading: Stack(
children: <Widget>[
GestureDetector(
child: Padding(
padding: EdgeInsets.only(top: 0.0, bottom: 0.0),
child: user.photoUrl.isNotEmpty
? CircleAvatar(
radius: 30.0,
backgroundColor: Colors.grey,
backgroundImage:
CachedNetworkImageProvider(
user.photoUrl),
)
: CircleAvatar(
radius: 30.0,
backgroundColor: Colors.grey,
),
),
onTap: () => Navigator.push(
context,
MaterialPageRoute(
builder: (context) => StoryPageView())),
),
],
),
title: Text(
user.profileName,
style: TextStyle(fontWeight: FontWeight.bold),
),
subtitle: Text("Add a Story"),
onTap: () => Navigator.push(
context,
MaterialPageRoute(
builder: (context) => CameraScreen())),
),
),
),
),
Padding(
padding: const EdgeInsets.all(8.0),
child: Text(
"Viewed Stories",
style: TextStyle(
color: Colors.grey,
fontWeight: FontWeight.bold,
),
),
),
Expanded(
child: Container(
padding: const EdgeInsets.all(0.0),
color: Colors.white,
child: ListView(
children: <Widget>[
Padding(
padding: const EdgeInsets.all(8.0),
child: ListTile(
leading: CircleAvatar(
radius: 30.0,
backgroundColor: Colors.grey,
),
title: Text(
"Username",
style: TextStyle(
fontWeight: FontWeight.bold,
),
),
subtitle: Text("Timestamp"),
onTap: () => Navigator.push(
context,
MaterialPageRoute(
builder: (context) => StoryPageView())),
),
),
],
),
),
),
],
),
);
}
},
);
}下面是CameraPage的构建器
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
backgroundColor: Colors.white,
iconTheme: IconThemeData(color: Colors.blue),
title: Text(
"Story Post",
style: TextStyle(
color: Colors.blue,
fontSize: 22.0,
),
),
),
body: file == null ? captureImageWithCamera() : displayStoryUploadScreen(),
);
}下面是完整的错误消息
══╡ EXCEPTION CAUGHT BY ANIMATION LIBRARY ╞═════════════════════════════════════════════════════════
The following assertion was thrown while notifying status listeners for AnimationController:
setState() or markNeedsBuild() called during build.
This _ModalScope<dynamic> 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:
_ModalScope<dynamic>-[LabeledGlobalKey<_ModalScopeState<dynamic>>#0c8ee]
The widget which was currently being built when the offending call was made was:
CameraScreen
When the exception was thrown, this was the stack:
[38;5;244m#0 Element.markNeedsBuild.<anonymous closure>[39;49m
[38;5;244m#1 Element.markNeedsBuild[39;49m
[38;5;244m#2 State.setState[39;49m
[38;5;244m#3 _ModalScopeState._routeSetState[39;49m
[38;5;244m#4 ModalRoute.setState[39;49m
[38;5;244m#5 ModalRoute.changedInternalState[39;49m
[38;5;244m#6 TransitionRoute._handleStatusChanged[39;49m
[38;5;244m#7 AnimationLocalStatusListenersMixin.notifyStatusListeners[39;49m
[38;5;244m#8 AnimationController._checkStatusChanged[39;49m
[38;5;244m#9 AnimationController._animateToInternal[39;49m
[38;5;244m#10 AnimationController.reverse[39;49m
[38;5;244m#11 TransitionRoute.didPop[39;49m
[38;5;244m#12 LocalHistoryRoute.didPop[39;49m
[38;5;244m#13 _RouteEntry.pop[39;49m
[38;5;244m#14 NavigatorState.pop[39;49m
[38;5;244m#15 Navigator.pop[39;49m
[38;5;248m#16 _CameraScreenState.captureImageWithCamera[39;49m
[38;5;248m#17 _CameraScreenState.build[39;49m
[38;5;244m#18 StatefulElement.build[39;49m
[38;5;244m#19 ComponentElement.performRebuild[39;49m
[38;5;244m#20 StatefulElement.performRebuild[39;49m
[38;5;244m#21 Element.rebuild[39;49m
[38;5;244m#22 ComponentElement._firstBuild[39;49m
[38;5;244m#23 StatefulElement._firstBuild[39;49m
[38;5;244m#24 ComponentElement.mount[39;49m
... Normal element mounting (24 frames)
[38;5;244m#48 Element.inflateWidget[39;49m
[38;5;244m#49 MultiChildRenderObjectElement.mount[39;49m
... Normal element mounting (136 frames)
[38;5;244m#185 Element.inflateWidget[39;49m
[38;5;244m#186 Element.updateChild[39;49m
[38;5;244m#187 RenderObjectElement.updateChildren[39;49m
[38;5;244m#188 MultiChildRenderObjectElement.update[39;49m
[38;5;244m#189 Element.updateChild[39;49m
[38;5;244m#190 ComponentElement.performRebuild[39;49m
[38;5;244m#191 StatefulElement.performRebuild[39;49m
[38;5;244m#192 Element.rebuild[39;49m
[38;5;244m#193 StatefulElement.update[39;49m
[38;5;244m#194 Element.updateChild[39;49m
[38;5;244m#195 ComponentElement.performRebuild[39;49m
[38;5;244m#196 Element.rebuild[39;49m
[38;5;244m#197 ProxyElement.update[39;49m
[38;5;244m#198 _InheritedNotifierElement.update[39;49m
[38;5;244m#199 Element.updateChild[39;49m
[38;5;244m#200 SingleChildRenderObjectElement.update[39;49m
[38;5;244m#201 Element.updateChild[39;49m
[38;5;244m#202 ComponentElement.performRebuild[39;49m
[38;5;244m#203 StatefulElement.performRebuild[39;49m
[38;5;244m#204 Element.rebuild[39;49m
[38;5;244m#205 StatefulElement.update[39;49m
[38;5;244m#206 Element.updateChild[39;49m
[38;5;244m#207 SingleChildRenderObjectElement.update[39;49m
[38;5;244m#208 Element.updateChild[39;49m
[38;5;244m#209 SingleChildRenderObjectElement.update[39;49m
[38;5;244m#210 Element.updateChild[39;49m
[38;5;244m#211 ComponentElement.performRebuild[39;49m
[38;5;244m#212 Element.rebuild[39;49m
[38;5;244m#213 StatelessElement.update[39;49m
[38;5;244m#214 Element.updateChild[39;49m
[38;5;244m#215 ComponentElement.performRebuild[39;49m
[38;5;244m#216 Element.rebuild[39;49m
[38;5;244m#217 ProxyElement.update[39;49m
[38;5;244m#218 Element.updateChild[39;49m
[38;5;244m#219 ComponentElement.performRebuild[39;49m
[38;5;244m#220 StatefulElement.performRebuild[39;49m
[38;5;244m#221 Element.rebuild[39;49m
[38;5;244m#222 BuildOwner.buildScope[39;49m
[38;5;244m#223 WidgetsBinding.drawFrame[39;49m
[38;5;244m#224 RendererBinding._handlePersistentFrameCallback[39;49m
[38;5;244m#225 SchedulerBinding._invokeFrameCallback[39;49m
[38;5;244m#226 SchedulerBinding.handleDrawFrame[39;49m
[38;5;244m#227 SchedulerBinding._handleDrawFrame[39;49m
[38;5;244m#231 _invoke (dart:ui/hooks.dart:253:10)[39;49m
[38;5;244m#232 _drawFrame (dart:ui/hooks.dart:211:3)[39;49m
(elided 3 frames from dart:async)
The AnimationController notifying status listeners was:
AnimationController#ac0aa(⏮ 0.000; paused; for MaterialPageRoute<dynamic>(null))
════════════════════════════════════════════════════════════════════════════════════════════════════
[38;5;248m════════ Exception caught by animation library ═════════════════════════════════[39;49m
[38;5;244mThe following assertion was thrown while notifying status listeners for AnimationController:[39;49m
setState() or markNeedsBuild() called during build.
[38;5;244mThis _ModalScope<dynamic> 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.[39;49m
[38;5;244mThe widget on which setState() or markNeedsBuild() was called was: _ModalScope<dynamic>-[LabeledGlobalKey<_ModalScopeState<dynamic>>#0c8ee][39;49m
[38;5;244mstate: _ModalScopeState<dynamic>#b0964[39;49m
[38;5;244mThe widget which was currently being built when the offending call was made was: CameraScreen[39;49m
[38;5;244mdirty[39;49m
[38;5;244mstate: _CameraScreenState#54b04[39;49m
[38;5;244mWhen the exception was thrown, this was the stack[39;49m
[38;5;244m#0 Element.markNeedsBuild.<anonymous closure>[39;49m
[38;5;244m#1 Element.markNeedsBuild[39;49m
[38;5;244m#2 State.setState[39;49m
[38;5;244m#3 _ModalScopeState._routeSetState[39;49m
[38;5;244m#4 ModalRoute.setState[39;49m
[38;5;244m...[39;49m
[38;5;244mThe AnimationController notifying status listeners was: AnimationController#ac0aa(⏮ 0.000; paused; for MaterialPageRoute<dynamic>(null))[39;49m
[38;5;248m════════════════════════════════════════════════════════════════════════════════[39;49m
Another exception was thrown: type 'Future<dynamic>' is not a subtype of type 'Widget'
[38;5;248m════════ Exception caught by widgets library ═══════════════════════════════════[39;49m
type 'Future<dynamic>' is not a subtype of type 'Widget'
[38;5;244mThe relevant error-causing widget was[39;49m
[38;5;248mCameraScreen[39;49m
[38;5;248m════════════════════════════════════════════════════════════════════════════════[39;49m回答 1
Stack Overflow用户
发布于 2020-09-11 04:32:26
MaterialPageRoute的builder函数应该从StatelessWidget或StatefullWidget返回一个小部件或类实现，显然CameraScreen不是这两个。
您的captureImageWithCamera将返回一个Future<void>，但scaffold的body必须是一个小部件，也不清楚displayStoryUploadScreen的返回类型是什么，但也必须是一个小部件。
如果您需要未来的值来构建您的小部件，那么您将需要使用FutureBuilder来等待它，而无需查看呈现树。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/63837092
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