从 TabBarView 的子项导航到另一页会引发错误

Question

我有一个 TabBar 可以在登录和注册之间切换，它们都是有状态的小部件。 Navigator 被注释时，没有报错。如果 Navigator 未被注释，则会抛出下面提到的错误。

下面提供相关代码-

Login/Register 选项卡视图

Flexible(
  child: TabBarView(
    children: [
      Login(), // A Stateful Widget,
      Register(),
    ],
  ),
),

登录提交按钮 -

Padding(
  padding: const EdgeInsets.only(top: 20.0),
  child: MaterialButton(
    color: Theme.of(context).accentColor,
    textColor: Colors.white,
    onPressed: loginPressed(context),
    child: Padding(
      padding: const EdgeInsets.all(15.0),
      child: Text('Login'),
    ),
  ),
),

函数 loginPressed() -

loginPressed(BuildContext context) {
  //Will Be conditions here right now redirection for sake of testing
  Navigator.pushReplacementNamed(context, 'home');
}

错误 -

I/flutter ( 4421): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter ( 4421): The following assertion was thrown building Login(dirty, dependencies: [_InheritedTheme,
I/flutter ( 4421): _LocalizationsScope-[GlobalKey#5872b]], state: _LoginState#6fe41):
I/flutter ( 4421): setState() or markNeedsBuild() called during build.
I/flutter ( 4421): This Overlay widget cannot be marked as needing to build because the framework is already in the
I/flutter ( 4421): process of building widgets.  A widget can be marked as needing to be built during the build phase
I/flutter ( 4421): only if one of its ancestors is currently building. This exception is allowed because the framework
I/flutter ( 4421): builds parent widgets before children, which means a dirty descendant will always be built.
I/flutter ( 4421): Otherwise, the framework might not visit this widget during this build phase.
I/flutter ( 4421): The widget on which setState() or markNeedsBuild() was called was:
I/flutter ( 4421):   Overlay-[LabeledGlobalKey<OverlayState>#e1e0c]
I/flutter ( 4421): The widget which was currently being built when the offending call was made was:
I/flutter ( 4421):   Login
I/flutter ( 4421): 
I/flutter ( 4421): The relevant error-causing widget was:
I/flutter ( 4421):   Login file:///D:/flutter_projects/project/lib/screens/login_reg.dart:50:23
I/flutter ( 4421): 
I/flutter ( 4421): When the exception was thrown, this was the stack:
I/flutter ( 4421): #0      Element.markNeedsBuild.<anonymous closure> (package:flutter/src/widgets/framework.dart:3896:11)
I/flutter ( 4421): #1      Element.markNeedsBuild (package:flutter/src/widgets/framework.dart:3911:6)
I/flutter ( 4421): #2      State.setState (package:flutter/src/widgets/framework.dart:1168:14)
I/flutter ( 4421): #3      OverlayState.insertAll (package:flutter/src/widgets/overlay.dart:344:5)
I/flutter ( 4421): #4      OverlayRoute.install (package:flutter/src/widgets/routes.dart:44:24)
I/flutter ( 4421): #5      TransitionRoute.install (package:flutter/src/widgets/routes.dart:181:11)
I/flutter ( 4421): #6      ModalRoute.install (package:flutter/src/widgets/routes.dart:959:11)
I/flutter ( 4421): #7      NavigatorState.pushReplacement (package:flutter/src/widgets/navigator.dart:1883:14)
I/flutter ( 4421): #8      NavigatorState.pushReplacementNamed (package:flutter/src/widgets/navigator.dart:1710:12)
I/flutter ( 4421): #9      Navigator.pushReplacementNamed (package:flutter/src/widgets/navigator.dart:972:34)
I/flutter ( 4421): #10     _LoginState.loginPressed (package:project/screens/login.dart:72:15)
I/flutter ( 4421): #11     _LoginState.build (package:project/screens/login.dart:57:30)
I/flutter ( 4421): #12     StatefulElement.build (package:flutter/src/widgets/framework.dart:4334:27)
I/flutter ( 4421): #13     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4223:15)
I/flutter ( 4421): #14     Element.rebuild (package:flutter/src/widgets/framework.dart:3947:5)
I/flutter ( 4421): #15     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:4206:5)
I/flutter ( 4421): #16     StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:4381:11)
I/flutter ( 4421): #17     ComponentElement.mount (package:flutter/src/widgets/framework.dart:4201:5)
I/flutter ( 4421): #18     Element.inflateWidget (package:flutter/src/widgets/framework.dart:3194:14)
I/flutter ( 4421): #19     Element.updateChild (package:flutter/src/widgets/framework.dart:2988:12)
I/flutter ( 4421): #20     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4243:16)
I/flutter ( 4421): #21     Element.rebuild (package:flutter/src/widgets/framework.dart:3947:5)
I/flutter ( 4421): #22     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:4206:5)
I/flutter ( 4421): #23     ComponentElement.mount (package:flutter/src/widgets/framework.dart:4201:5)
I/flutter ( 4421): #24     Element.inflateWidget (package:flutter/src/widgets/framework.dart:3194:14)
I/flutter ( 4421): #25     Element.updateChild (package:flutter/src/widgets/framework.dart:2988:12)
I/flutter ( 4421): #26     SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:5445:14)
I/flutter ( 4421): #27     Element.inflateWidget (package:flutter/src/widgets/framework.dart:3194:14)
I/flutter ( 4421): #28     Element.updateChild (package:flutter/src/widgets/framework.dart:2988:12)
I/flutter ( 4421): #29     SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:5445:14)
I/flutter ( 4421): #30     Element.inflateWidget (package:flutter/src/widgets/framework.dart:3194:14)
I/flutter ( 4421): #31     Element.updateChild (package:flutter/src/widgets/framework.dart:2988:12)
I/flutter ( 4421): #32     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4243:16)
I/flutter ( 4421): #33     Element.rebuild (package:flutter/src/widgets/framework.dart:3947:5)
I/flutter ( 4421): #34     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:4206:5)
I/flutter ( 4421): #35     ComponentElement.mount (package:flutter/src/widgets/framework.dart:4201:5)
I/flutter ( 4421): #36     Element.inflateWidget (package:flutter/src/widgets/framework.dart:3194:14)
I/flutter ( 4421): #37     Element.updateChild (package:flutter/src/widgets/framework.dart:2988:12)
I/flutter ( 4421): #38     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4243:16)
I/flutter ( 4421): #39     Element.rebuild (package:flutter/src/widgets/framework.dart:3947:5)
I/flutter ( 4421): #40     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:4206:5)
I/flutter ( 4421): #41     ComponentElement.mount (package:flutter/src/widgets/framework.dart:4201:5)
I/flutter ( 4421): #42     ParentDataElement.mount (package:flutter/src/widgets/framework.dart:4617:11)
I/flutter ( 4421): #43     Element.inflateWidget (package:flutter/src/widgets/framework.dart:3194:14)
I/flutter ( 4421): #44     Element.updateChild (package:flutter/src/widgets/framework.dart:2988:12)
I/flutter ( 4421): #45     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4243:16)
I/flutter ( 4421): #46     Element.rebuild (package:flutter/src/widgets/framework.dart:3947:5)
I/flutter ( 4421): #47     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:4206:5)
I/flutter ( 4421): #48     StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:4381:11)
I/flutter ( 4421): #49     ComponentElement.mount (package:flutter/src/widgets/framework.dart:4201:5)
I/flutter ( 4421): #50     Element.inflateWidget (package:flutter/src/widgets/framework.dart:3194:14)
I/flutter ( 4421): #51     Element.updateChild (package:flutter/src/widgets/framework.dart:2988:12)
I/flutter ( 4421): #52     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4243:16)
I/flutter ( 4421): #53     Element.rebuild (package:flutter/src/widgets/framework.dart:3947:5)
I/flutter ( 4421): #54     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:4206:5)
I/flutter ( 4421): #55     ComponentElement.mount (package:flutter/src/widgets/framework.dart:4201:5)
I/flutter ( 4421): #56     Element.inflateWidget (package:flutter/src/widgets/framework.dart:3194:14)
I/flutter ( 4421): #57     Element.updateChild (package:flutter/src/widgets/framework.dart:2988:12)
I/flutter ( 4421): #58     SliverMultiBoxAdaptorElement.updateChild (package:flutter/src/widgets/sliver.dart:1288:36)
I/flutter ( 4421): #59     SliverMultiBoxAdaptorElement.createChild.<anonymous closure> (package:flutter/src/widgets/sliver.dart:1273:20)
I/flutter ( 4421): #60     BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2412:19)
I/flutter ( 4421): #61     SliverMultiBoxAdaptorElement.createChild (package:flutter/src/widgets/sliver.dart:1266:11)
I/flutter ( 4421): #62     RenderSliverMultiBoxAdaptor._createOrObtainChild.<anonymous closure> (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:354:23)
I/flutter ( 4421): #63     RenderObject.invokeLayoutCallback.<anonymous closure> (package:flutter/src/rendering/object.dart:1823:58)
I/flutter ( 4421): #64     PipelineOwner._enableMutationsToDirtySubtrees (package:flutter/src/rendering/object.dart:875:15)
I/flutter ( 4421): #65     RenderObject.invokeLayoutCallback (package:flutter/src/rendering/object.dart:1823:13)
I/flutter ( 4421): #66     RenderSliverMultiBoxAdaptor._createOrObtainChild (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:343:5)
I/flutter ( 4421): #67     RenderSliverMultiBoxAdaptor.addInitialChild (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:427:5)
I/flutter ( 4421): #68     RenderSliverFixedExtentBoxAdaptor.performLayout (package:flutter/src/rendering/sliver_fixed_extent_list.dart:196:12)
I/flutter ( 4421): #69     RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #70     RenderSliverEdgeInsetsPadding.performLayout (package:flutter/src/rendering/sliver_padding.dart:134:11)
I/flutter ( 4421): #71     _RenderSliverFractionalPadding.performLayout (package:flutter/src/widgets/sliver.dart:1165:11)
I/flutter ( 4421): #72     RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #73     RenderViewportBase.layoutChildSequence (package:flutter/src/rendering/viewport.dart:410:13)
I/flutter ( 4421): #74     RenderViewport._attemptLayout (package:flutter/src/rendering/viewport.dart:1367:12)
I/flutter ( 4421): #75     RenderViewport.performLayout (package:flutter/src/rendering/viewport.dart:1285:20)
I/flutter ( 4421): #76     RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #77     RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter ( 4421): #78     RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #79     RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter ( 4421): #80     RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #81     RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter ( 4421): #82     RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #83     RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter ( 4421): #84     RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #85     RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter ( 4421): #86     RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #87     RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter ( 4421): #88     RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #89     RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter ( 4421): #90     RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #91     RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter ( 4421): #92     RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #93     RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter ( 4421): #94     RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #95     RenderFlex.performLayout (package:flutter/src/rendering/flex.dart:806:17)
I/flutter ( 4421): #96     RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #97     RenderPositionedBox.performLayout (package:flutter/src/rendering/shifted_box.dart:392:13)
I/flutter ( 4421): #98     RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #99     MultiChildLayoutDelegate.layoutChild (package:flutter/src/rendering/custom_layout.dart:163:11)
I/flutter ( 4421): #100    _ScaffoldLayout.performLayout (package:flutter/src/material/scaffold.dart:477:7)
I/flutter ( 4421): #101    MultiChildLayoutDelegate._callPerformLayout (package:flutter/src/rendering/custom_layout.dart:232:7)
I/flutter ( 4421): #102    RenderCustomMultiChildLayoutBox.performLayout (package:flutter/src/rendering/custom_layout.dart:391:14)
I/flutter ( 4421): #103    RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #104    RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter ( 4421): #105    RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #106    RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter ( 4421): #107    _RenderCustomClip.performLayout (package:flutter/src/rendering/proxy_box.dart:1232:11)
I/flutter ( 4421): #108    RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #109    RenderPadding.performLayout (package:flutter/src/rendering/shifted_box.dart:206:11)
I/flutter ( 4421): #110    RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #111    RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter ( 4421): #112    RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #113    RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter ( 4421): #114    RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #115    RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter ( 4421): #116    RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #117    RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter ( 4421): #118    RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #119    RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter ( 4421): #120    RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #121    RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter ( 4421): #122    RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #123    RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter ( 4421): #124    RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)
I/flutter ( 4421): #125    RenderOffstage.performLayout (package:flutter/src/rendering/proxy_box.dart:3166:14)
I/flutter ( 4421): #126    RenderObject.layout (package:flutter/src/rendering/object.dart:1724:7)

════════ Exception caught by widgets library ═══════════════════════════════════════════════════════
The following NoSuchMethodError was thrown building _OverlayEntry-[LabeledGlobalKey<_OverlayEntryState>#09487](dirty, state: _OverlayEntryState#46afb):
The getter 'status' was called on null.
Receiver: null
Tried calling: status

The relevant error-causing widget was: 
  MaterialApp file:///D:/flutter_projects/project/lib/main.dart:36:12
When the exception was thrown, this was the stack: 
#0      Object.noSuchMethod (dart:core-patch/object_patch.dart:53:5)
#1      ModalRoute._buildModalBarrier (package:flutter/src/widgets/routes.dart:1305:27)
#2      _OverlayEntryState.build (package:flutter/src/widgets/overlay.dart:169:25)
#3      StatefulElement.build (package:flutter/src/widgets/framework.dart:4334:27)
#4      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4223:15)
...
════════════════════════════════════════════════════════════════════════════════════════════════════

════════ Exception caught by widgets library ═══════════════════════════════════════════════════════
The method 'drive' was called on null.
Receiver: null
Tried calling: drive<Offset>(Instance of '_ChainedEvaluation<Offset>')
The relevant error-causing widget was: 
  MaterialApp file:///D:/flutter_projects/project/lib/main.dart:36:12
════════════════════════════════════════════════════════════════════════════════════════════════════
I/flutter ( 4421): #127    RenderStack.performLayout (package:flutter/src/rendering/stack.dart:505:15)
I/flutter ( 4421): #128    RenderObject._layoutWithoutResize (package:flutter/src/rendering/object.dart:1584:7)
I/flutter ( 4421): #129    PipelineOwner.flushLayout (package:flutter/src/rendering/object.dart:844:18)
I/flutter ( 4421): #130    RendererBinding.drawFrame (package:flutter/src/rendering/binding.dart:344:19)
I/flutter ( 4421): #131    WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:774:13)
I/flutter ( 4421): #132    RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:283:5)
I/flutter ( 4421): #133    SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1102:15)
I/flutter ( 4421): #134    SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1041:9)
I/flutter ( 4421): #135    SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:957:5)
I/flutter ( 4421): #139    _invoke (dart:ui/hooks.dart:259:10)
I/flutter ( 4421): #140    _drawFrame (dart:ui/hooks.dart:217:3)
I/flutter ( 4421): (elided 3 frames from package dart:async)
I/flutter ( 4421): 
I/flutter ( 4421): ════════════════════════════════════════════════════════════════════════════════════════════════════

不知道出了什么问题。

Answer 1

在您的小部件构建代码中，您正在调用 loginPressed 方法。请记住，当您编写以下代码时：

loginPressed(context)

实际上是calling/executing那个函数。因此，您实际上是在尝试在当前小部件仍在构建时导航到另一个页面。这就是您获得异常的原因。

您可以通过两种方式修复它：

方法一：

更改您的 onPressed 代码，例如：

onPressed: () {
   loginPressed(context);
}

方法二：

传递函数引用（您不需要传递上下文，函数已经可以访问它）：

onPressed:loginPressed,

并像这样更改函数：

 loginPressed() {
    Navigator.pushReplacementNamed(context, 'home');
 }

从 TabBarView 的子项导航到另一页会引发错误

Navigating to Another Page From TabBarView's child throws an error

dart

flutter

flutter-navigation

方法一：

方法二：