<h2 dir="auto">Steps to Reproduce</h2>
<p dir="auto">I'm trying to use tabs to navigate between multiple forms, at my first program I used the example at the cookbook, using the default controller. The problem occurs if I tap at the TextField on the first tab, then I go to the last tab and when I return to the first tab my program crashes, showing only a white screen, at my console I receive an huge exception stack.</p>
<p dir="auto">The only way I find to solve this problem was create a custom controller with a listener that remove the focus from the forms when navigating between tabs.</p>
<h2 dir="auto">My code</h2>
<div class="highlight highlight-source-dart notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="import 'package:dnd_cs/tabs/charInfo.dart';
import 'package:dnd_cs/tabs/charSkills.dart';
import 'package:dnd_cs/tabs/charEquip.dart';

class NewSheetForm extends StatefulWidget {
  @override
  _NewSheetFormState createState() =&gt; new _NewSheetFormState();
}

class _NewSheetFormState extends State&lt;NewSheetForm&gt; {
  CharInfo charInfoTab = new CharInfo();
  CharSkills charSkillsTab = new CharSkills();
  CharEquip charEquipTab = new CharEquip();

  @override
  Widget build(BuildContext context) {
    return new DefaultTabController(
        length: 3,
        child: new Scaffold(
          appBar: new AppBar(
            title: new Text('Dados do personagem'),
            bottom: new TabBar(
              tabs: [
                new Tab(
                  icon: new Icon(Icons.perm_identity),
                ),
                new Tab(
                  icon: new Icon(Icons.description),
                ),
                new Tab(
                  icon: new Icon(Icons.work),
                ),
              ],
            ),
          ),
          body: TabBarView(
              physics: new NeverScrollableScrollPhysics(),
              children: [charInfoTab, charSkillsTab, charEquipTab]),
        ),
    );
  }
}"><pre class="notranslate"><span class="pl-k">import</span> <span class="pl-s">'package:dnd_cs/tabs/charInfo.dart'</span>;
<span class="pl-k">import</span> <span class="pl-s">'package:dnd_cs/tabs/charSkills.dart'</span>;
<span class="pl-k">import</span> <span class="pl-s">'package:dnd_cs/tabs/charEquip.dart'</span>;

<span class="pl-k">class</span> <span class="pl-c1">NewSheetForm</span> <span class="pl-k">extends</span> <span class="pl-c1">StatefulWidget</span> {
  <span class="pl-k">@override</span>
  <span class="pl-c1">_NewSheetFormState</span> <span class="pl-en">createState</span>() <span class="pl-k">=&gt;</span> <span class="pl-k">new</span> <span class="pl-c1">_NewSheetFormState</span>();
}

<span class="pl-k">class</span> <span class="pl-c1">_NewSheetFormState</span> <span class="pl-k">extends</span> <span class="pl-c1">State</span>&lt;<span class="pl-c1">NewSheetForm</span>&gt; {
  <span class="pl-c1">CharInfo</span> charInfoTab <span class="pl-k">=</span> <span class="pl-k">new</span> <span class="pl-c1">CharInfo</span>();
  <span class="pl-c1">CharSkills</span> charSkillsTab <span class="pl-k">=</span> <span class="pl-k">new</span> <span class="pl-c1">CharSkills</span>();
  <span class="pl-c1">CharEquip</span> charEquipTab <span class="pl-k">=</span> <span class="pl-k">new</span> <span class="pl-c1">CharEquip</span>();

  <span class="pl-k">@override</span>
  <span class="pl-c1">Widget</span> <span class="pl-en">build</span>(<span class="pl-c1">BuildContext</span> context) {
    <span class="pl-k">return</span> <span class="pl-k">new</span> <span class="pl-c1">DefaultTabController</span>(
        length<span class="pl-k">:</span> <span class="pl-c1">3</span>,
        child<span class="pl-k">:</span> <span class="pl-k">new</span> <span class="pl-c1">Scaffold</span>(
          appBar<span class="pl-k">:</span> <span class="pl-k">new</span> <span class="pl-c1">AppBar</span>(
            title<span class="pl-k">:</span> <span class="pl-k">new</span> <span class="pl-c1">Text</span>(<span class="pl-s">'Dados do personagem'</span>),
            bottom<span class="pl-k">:</span> <span class="pl-k">new</span> <span class="pl-c1">TabBar</span>(
              tabs<span class="pl-k">:</span> [
                <span class="pl-k">new</span> <span class="pl-c1">Tab</span>(
                  icon<span class="pl-k">:</span> <span class="pl-k">new</span> <span class="pl-c1">Icon</span>(<span class="pl-c1">Icons</span>.perm_identity),
                ),
                <span class="pl-k">new</span> <span class="pl-c1">Tab</span>(
                  icon<span class="pl-k">:</span> <span class="pl-k">new</span> <span class="pl-c1">Icon</span>(<span class="pl-c1">Icons</span>.description),
                ),
                <span class="pl-k">new</span> <span class="pl-c1">Tab</span>(
                  icon<span class="pl-k">:</span> <span class="pl-k">new</span> <span class="pl-c1">Icon</span>(<span class="pl-c1">Icons</span>.work),
                ),
              ],
            ),
          ),
          body<span class="pl-k">:</span> <span class="pl-c1">TabBarView</span>(
              physics<span class="pl-k">:</span> <span class="pl-k">new</span> <span class="pl-c1">NeverScrollableScrollPhysics</span>(),
              children<span class="pl-k">:</span> [charInfoTab, charSkillsTab, charEquipTab]),
        ),
    );
  }
}</pre></div>
<p dir="auto">First tab</p>
<div class="highlight highlight-source-dart notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="import 'package:flutter/material.dart';

class CharInfo extends StatefulWidget {
  @override
  _CharInfoState createState() =&gt; new _CharInfoState();
}

class _CharInfoState extends State&lt;CharInfo&gt;{
  GlobalKey&lt;FormState&gt; _formKey = new GlobalKey&lt;FormState&gt;();

  @override
  Widget build(BuildContext context) {
    return new Container(
      child: new SafeArea(
        top: false,
        bottom: false,
        child: new Form(
          key: _formKey,
          autovalidate: true,
          child: new ListView(
            padding: const EdgeInsets.symmetric(horizontal: 20.0),
            children: &lt;Widget&gt;[
              new TextFormField(
                decoration: const InputDecoration(
                  icon: const Icon(Icons.person),
                  hintText: 'Seu nome',
                  labelText: 'Nome',
                ),
              ),
              new TextFormField(
                decoration: const InputDecoration(
                  icon: const Icon(Icons.whatshot),
                  hintText: 'Neutro',
                  labelText: 'Alinhamento',
                ),
              ),
              new TextFormField(
                decoration: const InputDecoration(
                  icon: const Icon(Icons.translate),
                  hintText: 'Idioma comum',
                  labelText: 'Idiomas',
                ),
              ),
              new TextFormField(
                keyboardType: TextInputType.number,
                decoration: const InputDecoration(
                  icon: const Icon(Icons.trending_up),
                  //hintText: 'Idioma comum',
                  labelText: 'Nível',
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}"><pre class="notranslate"><span class="pl-k">import</span> <span class="pl-s">'package:flutter/material.dart'</span>;

<span class="pl-k">class</span> <span class="pl-c1">CharInfo</span> <span class="pl-k">extends</span> <span class="pl-c1">StatefulWidget</span> {
  <span class="pl-k">@override</span>
  <span class="pl-c1">_CharInfoState</span> <span class="pl-en">createState</span>() <span class="pl-k">=&gt;</span> <span class="pl-k">new</span> <span class="pl-c1">_CharInfoState</span>();
}

<span class="pl-k">class</span> <span class="pl-c1">_CharInfoState</span> <span class="pl-k">extends</span> <span class="pl-c1">State</span>&lt;<span class="pl-c1">CharInfo</span>&gt;{
  <span class="pl-c1">GlobalKey</span>&lt;<span class="pl-c1">FormState</span>&gt; _formKey <span class="pl-k">=</span> <span class="pl-k">new</span> <span class="pl-c1">GlobalKey</span>&lt;<span class="pl-c1">FormState</span>&gt;();

  <span class="pl-k">@override</span>
  <span class="pl-c1">Widget</span> <span class="pl-en">build</span>(<span class="pl-c1">BuildContext</span> context) {
    <span class="pl-k">return</span> <span class="pl-k">new</span> <span class="pl-c1">Container</span>(
      child<span class="pl-k">:</span> <span class="pl-k">new</span> <span class="pl-c1">SafeArea</span>(
        top<span class="pl-k">:</span> <span class="pl-c1">false</span>,
        bottom<span class="pl-k">:</span> <span class="pl-c1">false</span>,
        child<span class="pl-k">:</span> <span class="pl-k">new</span> <span class="pl-c1">Form</span>(
          key<span class="pl-k">:</span> _formKey,
          autovalidate<span class="pl-k">:</span> <span class="pl-c1">true</span>,
          child<span class="pl-k">:</span> <span class="pl-k">new</span> <span class="pl-c1">ListView</span>(
            padding<span class="pl-k">:</span> <span class="pl-k">const</span> <span class="pl-c1">EdgeInsets</span>.<span class="pl-en">symmetric</span>(horizontal<span class="pl-k">:</span> <span class="pl-c1">20.0</span>),
            children<span class="pl-k">:</span> <span class="pl-k">&lt;</span><span class="pl-c1">Widget</span><span class="pl-k">&gt;</span>[
              <span class="pl-k">new</span> <span class="pl-c1">TextFormField</span>(
                decoration<span class="pl-k">:</span> <span class="pl-k">const</span> <span class="pl-c1">InputDecoration</span>(
                  icon<span class="pl-k">:</span> <span class="pl-k">const</span> <span class="pl-c1">Icon</span>(<span class="pl-c1">Icons</span>.person),
                  hintText<span class="pl-k">:</span> <span class="pl-s">'Seu nome'</span>,
                  labelText<span class="pl-k">:</span> <span class="pl-s">'Nome'</span>,
                ),
              ),
              <span class="pl-k">new</span> <span class="pl-c1">TextFormField</span>(
                decoration<span class="pl-k">:</span> <span class="pl-k">const</span> <span class="pl-c1">InputDecoration</span>(
                  icon<span class="pl-k">:</span> <span class="pl-k">const</span> <span class="pl-c1">Icon</span>(<span class="pl-c1">Icons</span>.whatshot),
                  hintText<span class="pl-k">:</span> <span class="pl-s">'Neutro'</span>,
                  labelText<span class="pl-k">:</span> <span class="pl-s">'Alinhamento'</span>,
                ),
              ),
              <span class="pl-k">new</span> <span class="pl-c1">TextFormField</span>(
                decoration<span class="pl-k">:</span> <span class="pl-k">const</span> <span class="pl-c1">InputDecoration</span>(
                  icon<span class="pl-k">:</span> <span class="pl-k">const</span> <span class="pl-c1">Icon</span>(<span class="pl-c1">Icons</span>.translate),
                  hintText<span class="pl-k">:</span> <span class="pl-s">'Idioma comum'</span>,
                  labelText<span class="pl-k">:</span> <span class="pl-s">'Idiomas'</span>,
                ),
              ),
              <span class="pl-k">new</span> <span class="pl-c1">TextFormField</span>(
                keyboardType<span class="pl-k">:</span> <span class="pl-c1">TextInputType</span>.number,
                decoration<span class="pl-k">:</span> <span class="pl-k">const</span> <span class="pl-c1">InputDecoration</span>(
                  icon<span class="pl-k">:</span> <span class="pl-k">const</span> <span class="pl-c1">Icon</span>(<span class="pl-c1">Icons</span>.trending_up),
                  <span class="pl-c">//hintText: 'Idioma comum',</span>
                  labelText<span class="pl-k">:</span> <span class="pl-s">'Nível'</span>,
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}</pre></div>
<p dir="auto">Second and third tabs</p>
<div class="highlight highlight-source-dart notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="import 'package:flutter/material.dart';

class CharSkills extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new Container(
      child: new Center(
        child: new Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: &lt;Widget&gt;[
            new Icon(
              Icons.business_center,
              size: 160.0,
              color: Colors.red,
            ),
            new Text('Second Tab'),
          ],
        ),
      ),
    );
  }
}"><pre class="notranslate"><span class="pl-k">import</span> <span class="pl-s">'package:flutter/material.dart'</span>;

<span class="pl-k">class</span> <span class="pl-c1">CharSkills</span> <span class="pl-k">extends</span> <span class="pl-c1">StatelessWidget</span> {
  <span class="pl-k">@override</span>
  <span class="pl-c1">Widget</span> <span class="pl-en">build</span>(<span class="pl-c1">BuildContext</span> context) {
    <span class="pl-k">return</span> <span class="pl-k">new</span> <span class="pl-c1">Container</span>(
      child<span class="pl-k">:</span> <span class="pl-k">new</span> <span class="pl-c1">Center</span>(
        child<span class="pl-k">:</span> <span class="pl-k">new</span> <span class="pl-c1">Column</span>(
          mainAxisAlignment<span class="pl-k">:</span> <span class="pl-c1">MainAxisAlignment</span>.center,
          children<span class="pl-k">:</span> <span class="pl-k">&lt;</span><span class="pl-c1">Widget</span><span class="pl-k">&gt;</span>[
            <span class="pl-k">new</span> <span class="pl-c1">Icon</span>(
              <span class="pl-c1">Icons</span>.business_center,
              size<span class="pl-k">:</span> <span class="pl-c1">160.0</span>,
              color<span class="pl-k">:</span> <span class="pl-c1">Colors</span>.red,
            ),
            <span class="pl-k">new</span> <span class="pl-c1">Text</span>(<span class="pl-s">'Second Tab'</span>),
          ],
        ),
      ),
    );
  }
}</pre></div>
<h2 dir="auto">Logs</h2>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="Showing Moto G 4 logs:
I/flutter ( 2926): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter ( 2926): The following assertion was thrown building NotificationListener&lt;KeepAliveNotification&gt;:
I/flutter ( 2926): 'package:flutter/src/rendering/object.dart': Failed assertion: line 2775 pos 14:
I/flutter ( 2926): '_debugUltimatePreviousSiblingOf(after, equals: _firstChild)': is not true.
I/flutter ( 2926): 
I/flutter ( 2926): Either the assertion indicates an error in the framework itself, or we should provide substantially
I/flutter ( 2926): more information in this error message to help you determine and fix the underlying cause.
I/flutter ( 2926): In either case, please report this assertion by filing a bug on GitHub:
I/flutter ( 2926):   https://github.com/flutter/flutter/issues/new
I/flutter ( 2926): 
I/flutter ( 2926): When the exception was thrown, this was the stack:
I/flutter ( 2926): #2      _RenderSliverMultiBoxAdaptor&amp;RenderSliver&amp;ContainerRenderObjectMixin._insertIntoChildList (package:flutter/src/rendering/object.dart)
I/flutter ( 2926): #3      _RenderSliverMultiBoxAdaptor&amp;RenderSliver&amp;ContainerRenderObjectMixin.insert (package:flutter/src/rendering/object.dart:2809:5)
I/flutter ( 2926): #4      RenderSliverMultiBoxAdaptor.insert (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:209:11)
I/flutter ( 2926): #5      SliverMultiBoxAdaptorElement.insertChildRenderObject (package:flutter/src/widgets/sliver.dart:865:18)
I/flutter ( 2926): #6      RenderObjectElement.attachRenderObject (package:flutter/src/widgets/framework.dart:4513:35)
I/flutter ( 2926): #7      RenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4279:5)
I/flutter ( 2926): #8      SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4653:11)
I/flutter ( 2926): #9      Element.inflateWidget (package:flutter/src/widgets/framework.dart:2907:14)
I/flutter ( 2926): #10     Element.updateChild (package:flutter/src/widgets/framework.dart:2710:12)
I/flutter ( 2926): #11     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #12     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #13     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3622:5)
I/flutter ( 2926): #14     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3617:5)
I/flutter ( 2926): #15     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2907:14)
I/flutter ( 2926): #16     Element.updateChild (package:flutter/src/widgets/framework.dart:2710:12)
I/flutter ( 2926): #17     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #18     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #19     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3622:5)
I/flutter ( 2926): #20     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3617:5)
I/flutter ( 2926): #21     ParentDataElement.mount (package:flutter/src/widgets/framework.dart:3955:11)
I/flutter ( 2926): #22     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2907:14)
I/flutter ( 2926): #23     Element.updateChild (package:flutter/src/widgets/framework.dart:2710:12)
I/flutter ( 2926): #24     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #25     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #26     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3622:5)
I/flutter ( 2926): #27     StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3769:11)
I/flutter ( 2926): #28     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3617:5)
I/flutter ( 2926): #29     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2907:14)
I/flutter ( 2926): #30     Element.updateChild (package:flutter/src/widgets/framework.dart:2710:12)
I/flutter ( 2926): #31     SliverMultiBoxAdaptorElement.updateChild (package:flutter/src/widgets/sliver.dart:744:36)
I/flutter ( 2926): #32     SliverMultiBoxAdaptorElement.performRebuild (package:flutter/src/widgets/sliver.dart:702:34)
I/flutter ( 2926): #33     SliverMultiBoxAdaptorElement.update (package:flutter/src/widgets/sliver.dart:671:7)
I/flutter ( 2926): #34     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #35     RenderObjectElement.updateChildren (package:flutter/src/widgets/framework.dart:4379:32)
I/flutter ( 2926): #36     MultiChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4769:17)
I/flutter ( 2926): #37     _ViewportElement.update (package:flutter/src/widgets/viewport.dart:192:11)
I/flutter ( 2926): #38     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #39     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #40     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #41     ProxyElement.update (package:flutter/src/widgets/framework.dart:3909:5)
I/flutter ( 2926): #42     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #43     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 2926): #44     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #45     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 2926): #46     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #47     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 2926): #48     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #49     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 2926): #50     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #51     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #52     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #53     StatefulElement.update (package:flutter/src/widgets/framework.dart:3799:5)
I/flutter ( 2926): #54     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #55     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 2926): #56     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #57     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 2926): #58     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #59     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 2926): #60     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #61     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 2926): #62     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #63     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #64     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #65     StatelessElement.update (package:flutter/src/widgets/framework.dart:3702:5)
I/flutter ( 2926): #66     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #67     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #68     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #69     StatefulElement.update (package:flutter/src/widgets/framework.dart:3799:5)
I/flutter ( 2926): #70     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #71     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #72     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #73     StatefulElement.update (package:flutter/src/widgets/framework.dart:3799:5)
I/flutter ( 2926): #74     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #75     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #76     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #77     StatelessElement.update (package:flutter/src/widgets/framework.dart:3702:5)
I/flutter ( 2926): #78     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #79     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #80     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #81     StatefulElement.update (package:flutter/src/widgets/framework.dart:3799:5)
I/flutter ( 2926): #82     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #83     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #84     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #85     StatelessElement.update (package:flutter/src/widgets/framework.dart:3702:5)
I/flutter ( 2926): #86     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #87     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #88     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #89     BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2242:33)
I/flutter ( 2926): #90     _WidgetsFlutterBinding&amp;BindingBase&amp;GestureBinding&amp;ServicesBinding&amp;SchedulerBinding&amp;PaintingBinding&amp;RendererBinding&amp;WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:626:20)
I/flutter ( 2926): #91     _WidgetsFlutterBinding&amp;BindingBase&amp;GestureBinding&amp;ServicesBinding&amp;SchedulerBinding&amp;PaintingBinding&amp;RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:208:5)
I/flutter ( 2926): #92     _WidgetsFlutterBinding&amp;BindingBase&amp;GestureBinding&amp;ServicesBinding&amp;SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:990:15)
I/flutter ( 2926): #93     _WidgetsFlutterBinding&amp;BindingBase&amp;GestureBinding&amp;ServicesBinding&amp;SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:930:9)
I/flutter ( 2926): #94     _WidgetsFlutterBinding&amp;BindingBase&amp;GestureBinding&amp;ServicesBinding&amp;SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:842:5)
I/flutter ( 2926): #95     _invoke (dart:ui/hooks.dart:120:13)
I/flutter ( 2926): #96     _drawFrame (dart:ui/hooks.dart:109:3)
I/flutter ( 2926): (elided 2 frames from class _AssertionError)
I/flutter ( 2926): ════════════════════════════════════════════════════════════════════════════════════════════════════
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/rendering/object.dart': Failed assertion: line 2775 pos 14: '_debugUltimatePreviousSiblingOf(after, equals: _firstChild)': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/rendering/object.dart': Failed assertion: line 2775 pos 14: '_debugUltimatePreviousSiblingOf(after, equals: _firstChild)': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/rendering/object.dart': Failed assertion: line 2775 pos 14: '_debugUltimatePreviousSiblingOf(after, equals: _firstChild)': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 2926): Another exception was thrown: The _ScaffoldLayout custom multichild layout delegate forgot to lay out the following children:
I/flutter ( 2926): Another exception was thrown: type 'RenderErrorBox' is not a subtype of type 'RenderSemanticsGestureHandler'
I/flutter ( 2926): Another exception was thrown: The _ScaffoldLayout custom multichild layout delegate forgot to lay out the following children:
I/flutter ( 2926): Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#1290f NEEDS-LAYOUT NEEDS-PAINT
I/flutter ( 2926): Another exception was thrown: The _ScaffoldLayout custom multichild layout delegate forgot to lay out the following children:
I/flutter ( 2926): Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#1290f NEEDS-LAYOUT NEEDS-PAINT
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 4039 pos 14: '_dependents.isEmpty': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 2240 pos 16: '!_dirtyElements[index]._active || _dirtyElements[index]._debugIsInScope(context)': is not true."><pre class="notranslate"><code class="notranslate">Showing Moto G 4 logs:
I/flutter ( 2926): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter ( 2926): The following assertion was thrown building NotificationListener&lt;KeepAliveNotification&gt;:
I/flutter ( 2926): 'package:flutter/src/rendering/object.dart': Failed assertion: line 2775 pos 14:
I/flutter ( 2926): '_debugUltimatePreviousSiblingOf(after, equals: _firstChild)': is not true.
I/flutter ( 2926): 
I/flutter ( 2926): Either the assertion indicates an error in the framework itself, or we should provide substantially
I/flutter ( 2926): more information in this error message to help you determine and fix the underlying cause.
I/flutter ( 2926): In either case, please report this assertion by filing a bug on GitHub:
I/flutter ( 2926):   https://github.com/flutter/flutter/issues/new
I/flutter ( 2926): 
I/flutter ( 2926): When the exception was thrown, this was the stack:
I/flutter ( 2926): #2      _RenderSliverMultiBoxAdaptor&amp;RenderSliver&amp;ContainerRenderObjectMixin._insertIntoChildList (package:flutter/src/rendering/object.dart)
I/flutter ( 2926): #3      _RenderSliverMultiBoxAdaptor&amp;RenderSliver&amp;ContainerRenderObjectMixin.insert (package:flutter/src/rendering/object.dart:2809:5)
I/flutter ( 2926): #4      RenderSliverMultiBoxAdaptor.insert (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:209:11)
I/flutter ( 2926): #5      SliverMultiBoxAdaptorElement.insertChildRenderObject (package:flutter/src/widgets/sliver.dart:865:18)
I/flutter ( 2926): #6      RenderObjectElement.attachRenderObject (package:flutter/src/widgets/framework.dart:4513:35)
I/flutter ( 2926): #7      RenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4279:5)
I/flutter ( 2926): #8      SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4653:11)
I/flutter ( 2926): #9      Element.inflateWidget (package:flutter/src/widgets/framework.dart:2907:14)
I/flutter ( 2926): #10     Element.updateChild (package:flutter/src/widgets/framework.dart:2710:12)
I/flutter ( 2926): #11     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #12     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #13     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3622:5)
I/flutter ( 2926): #14     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3617:5)
I/flutter ( 2926): #15     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2907:14)
I/flutter ( 2926): #16     Element.updateChild (package:flutter/src/widgets/framework.dart:2710:12)
I/flutter ( 2926): #17     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #18     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #19     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3622:5)
I/flutter ( 2926): #20     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3617:5)
I/flutter ( 2926): #21     ParentDataElement.mount (package:flutter/src/widgets/framework.dart:3955:11)
I/flutter ( 2926): #22     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2907:14)
I/flutter ( 2926): #23     Element.updateChild (package:flutter/src/widgets/framework.dart:2710:12)
I/flutter ( 2926): #24     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #25     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #26     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3622:5)
I/flutter ( 2926): #27     StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3769:11)
I/flutter ( 2926): #28     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3617:5)
I/flutter ( 2926): #29     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2907:14)
I/flutter ( 2926): #30     Element.updateChild (package:flutter/src/widgets/framework.dart:2710:12)
I/flutter ( 2926): #31     SliverMultiBoxAdaptorElement.updateChild (package:flutter/src/widgets/sliver.dart:744:36)
I/flutter ( 2926): #32     SliverMultiBoxAdaptorElement.performRebuild (package:flutter/src/widgets/sliver.dart:702:34)
I/flutter ( 2926): #33     SliverMultiBoxAdaptorElement.update (package:flutter/src/widgets/sliver.dart:671:7)
I/flutter ( 2926): #34     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #35     RenderObjectElement.updateChildren (package:flutter/src/widgets/framework.dart:4379:32)
I/flutter ( 2926): #36     MultiChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4769:17)
I/flutter ( 2926): #37     _ViewportElement.update (package:flutter/src/widgets/viewport.dart:192:11)
I/flutter ( 2926): #38     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #39     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #40     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #41     ProxyElement.update (package:flutter/src/widgets/framework.dart:3909:5)
I/flutter ( 2926): #42     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #43     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 2926): #44     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #45     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 2926): #46     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #47     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 2926): #48     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #49     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 2926): #50     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #51     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #52     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #53     StatefulElement.update (package:flutter/src/widgets/framework.dart:3799:5)
I/flutter ( 2926): #54     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #55     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 2926): #56     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #57     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 2926): #58     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #59     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 2926): #60     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #61     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4661:14)
I/flutter ( 2926): #62     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #63     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #64     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #65     StatelessElement.update (package:flutter/src/widgets/framework.dart:3702:5)
I/flutter ( 2926): #66     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #67     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #68     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #69     StatefulElement.update (package:flutter/src/widgets/framework.dart:3799:5)
I/flutter ( 2926): #70     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #71     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #72     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #73     StatefulElement.update (package:flutter/src/widgets/framework.dart:3799:5)
I/flutter ( 2926): #74     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #75     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #76     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #77     StatelessElement.update (package:flutter/src/widgets/framework.dart:3702:5)
I/flutter ( 2926): #78     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #79     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #80     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #81     StatefulElement.update (package:flutter/src/widgets/framework.dart:3799:5)
I/flutter ( 2926): #82     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #83     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #84     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #85     StatelessElement.update (package:flutter/src/widgets/framework.dart:3702:5)
I/flutter ( 2926): #86     Element.updateChild (package:flutter/src/widgets/framework.dart:2699:15)
I/flutter ( 2926): #87     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3653:16)
I/flutter ( 2926): #88     Element.rebuild (package:flutter/src/widgets/framework.dart:3495:5)
I/flutter ( 2926): #89     BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2242:33)
I/flutter ( 2926): #90     _WidgetsFlutterBinding&amp;BindingBase&amp;GestureBinding&amp;ServicesBinding&amp;SchedulerBinding&amp;PaintingBinding&amp;RendererBinding&amp;WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:626:20)
I/flutter ( 2926): #91     _WidgetsFlutterBinding&amp;BindingBase&amp;GestureBinding&amp;ServicesBinding&amp;SchedulerBinding&amp;PaintingBinding&amp;RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:208:5)
I/flutter ( 2926): #92     _WidgetsFlutterBinding&amp;BindingBase&amp;GestureBinding&amp;ServicesBinding&amp;SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:990:15)
I/flutter ( 2926): #93     _WidgetsFlutterBinding&amp;BindingBase&amp;GestureBinding&amp;ServicesBinding&amp;SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:930:9)
I/flutter ( 2926): #94     _WidgetsFlutterBinding&amp;BindingBase&amp;GestureBinding&amp;ServicesBinding&amp;SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:842:5)
I/flutter ( 2926): #95     _invoke (dart:ui/hooks.dart:120:13)
I/flutter ( 2926): #96     _drawFrame (dart:ui/hooks.dart:109:3)
I/flutter ( 2926): (elided 2 frames from class _AssertionError)
I/flutter ( 2926): ════════════════════════════════════════════════════════════════════════════════════════════════════
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/rendering/object.dart': Failed assertion: line 2775 pos 14: '_debugUltimatePreviousSiblingOf(after, equals: _firstChild)': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/rendering/object.dart': Failed assertion: line 2775 pos 14: '_debugUltimatePreviousSiblingOf(after, equals: _firstChild)': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/rendering/object.dart': Failed assertion: line 2775 pos 14: '_debugUltimatePreviousSiblingOf(after, equals: _firstChild)': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 2926): Another exception was thrown: The _ScaffoldLayout custom multichild layout delegate forgot to lay out the following children:
I/flutter ( 2926): Another exception was thrown: type 'RenderErrorBox' is not a subtype of type 'RenderSemanticsGestureHandler'
I/flutter ( 2926): Another exception was thrown: The _ScaffoldLayout custom multichild layout delegate forgot to lay out the following children:
I/flutter ( 2926): Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#1290f NEEDS-LAYOUT NEEDS-PAINT
I/flutter ( 2926): Another exception was thrown: The _ScaffoldLayout custom multichild layout delegate forgot to lay out the following children:
I/flutter ( 2926): Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#1290f NEEDS-LAYOUT NEEDS-PAINT
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 4039 pos 14: '_dependents.isEmpty': is not true.
I/flutter ( 2926): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 2240 pos 16: '!_dirtyElements[index]._active || _dirtyElements[index]._debugIsInScope(context)': is not true.
</code></pre></div>
<h2 dir="auto">Steps to Reproduce</h2>
<p dir="auto">I have a PageView that contains the top level widgets for my app, with switching between them controlled by a BottomNavBar. As per <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/Hixie/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://github.com/Hixie">@Hixie</a>'s advice in the chat, I am adding <code class="notranslate">AutomaticKeepAliveClientMixin</code> to these top level widgets so the PageView won't recycle them and will preserve state. After I added this to the main widget that contains a network loaded ListView, on occasion when switching back to this ListView from another tab I get this failed assertion in the framework.</p>
<h2 dir="auto">Logs</h2>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
The following assertion was thrown building NotificationListener&lt;KeepAliveNotification&gt;:
'package:flutter/src/rendering/object.dart': Failed assertion: line 3031 pos 14:
'_debugUltimatePreviousSiblingOf(after, equals: _firstChild)': is not true.
Either the assertion indicates an error in the framework itself, or we should provide substantially
more information in this error message to help you determine and fix the underlying cause.
In either case, please report this assertion by filing a bug on GitHub:
  https://github.com/flutter/flutter/issues/new
When the exception was thrown, this was the stack:
#2      RenderSliver&amp;ContainerRenderObjectMixin._insertIntoChildList (package:flutter/src/rendering/object.dart:3031:14)
#3      RenderSliver&amp;ContainerRenderObjectMixin.insert (package:flutter/src/rendering/object.dart:3065:5)
#4      RenderSliverMultiBoxAdaptor.insert (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:193:17)
#5      SliverMultiBoxAdaptorElement.insertChildRenderObject (package:flutter/src/widgets/sliver.dart:840:18)
#6      RenderObjectElement.attachRenderObject (package:flutter/src/widgets/framework.dart:4380:35)
#7      RenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4151:5)
#8      SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4515:16)
#9      Element.inflateWidget (package:flutter/src/widgets/framework.dart:2882:14)
#10     Element.updateChild (package:flutter/src/widgets/framework.dart:2685:12)
#11     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#12     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#13     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3514:5)
#14     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3509:5)
#15     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2882:14)
#16     Element.updateChild (package:flutter/src/widgets/framework.dart:2685:12)
#17     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#18     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#19     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3514:5)
#20     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3509:5)
#21     ParentDataElement.mount (package:flutter/src/widgets/framework.dart:3827:16)
#22     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2882:14)
#23     Element.updateChild (package:flutter/src/widgets/framework.dart:2685:12)
#24     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#25     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#26     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3514:5)
#27     StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3652:22)
#28     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3509:5)
#29     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2882:14)
#30     Element.updateChild (package:flutter/src/widgets/framework.dart:2685:12)
#31     SliverMultiBoxAdaptorElement.performRebuild (package:flutter/src/widgets/sliver.dart:696:34)
#32     SliverMultiBoxAdaptorElement.update (package:flutter/src/widgets/sliver.dart:665:7)
#33     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#34     RenderObjectElement.updateChildren (package:flutter/src/widgets/framework.dart:4250:32)
#35     MultiChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4631:17)
#36     _ViewportElement.update (package:flutter/src/widgets/viewport.dart:150:17)
#37     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#38     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#39     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#40     ProxyElement.update (package:flutter/src/widgets/framework.dart:3781:5)
#41     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#42     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4523:14)
#43     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#44     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4523:14)
#45     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#46     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4523:14)
#47     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#48     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#49     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#50     StatefulElement.update (package:flutter/src/widgets/framework.dart:3671:5)
#51     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#52     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#53     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#54     StatefulElement.update (package:flutter/src/widgets/framework.dart:3671:5)
#55     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#56     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#57     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#58     StatelessElement.update (package:flutter/src/widgets/framework.dart:3596:5)
#59     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#60     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#61     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#62     StatefulElement.update (package:flutter/src/widgets/framework.dart:3671:5)
#63     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#64     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#65     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#66     ProxyElement.update (package:flutter/src/widgets/framework.dart:3781:5)
#67     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#68     RenderObjectElement.updateChildren (package:flutter/src/widgets/framework.dart:4250:32)
#69     MultiChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4631:17)
#70     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#71     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#72     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#73     ProxyElement.update (package:flutter/src/widgets/framework.dart:3781:5)
#74     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#75     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#76     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#77     StatefulElement.update (package:flutter/src/widgets/framework.dart:3671:5)
#78     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#79     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4523:14)
#80     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#81     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#82     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#83     StatelessElement.update (package:flutter/src/widgets/framework.dart:3596:5)
#84     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#85     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4523:14)
#86     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#87     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#88     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#89     StatefulElement.update (package:flutter/src/widgets/framework.dart:3671:5)
#90     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#91     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#92     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#93     StatefulElement.update (package:flutter/src/widgets/framework.dart:3671:5)
#94     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#95     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#96     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#97     ProxyElement.update (package:flutter/src/widgets/framework.dart:3781:5)
#98     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#99     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#100    Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#101    ProxyElement.update (package:flutter/src/widgets/framework.dart:3781:5)
#102    Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#103    ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#104    Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#105    StatefulElement.update (package:flutter/src/widgets/framework.dart:3671:5)
#106    Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#107    ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#108    Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#109    BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2260:33)
#110    BindingBase&amp;SchedulerBinding&amp;GestureBinding&amp;ServicesBinding&amp;RendererBinding&amp;WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:503:20)
#111    BindingBase&amp;SchedulerBinding&amp;GestureBinding&amp;ServicesBinding&amp;RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:189:5)
#112    BindingBase&amp;SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:695:15)
#113    BindingBase&amp;SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:643:9)
#114    _invoke (file:///b/build/slave/Mac_Engine/build/src/flutter/lib/ui/hooks.dart:86)
#115    _drawFrame (file:///b/build/slave/Mac_Engine/build/src/flutter/lib/ui/hooks.dart:75)
(elided 2 frames from class _AssertionError)
════════════════════════════════════════════════════════════════════════════════════════════════════
Another exception was thrown: 'package:flutter/src/rendering/object.dart': Failed assertion: line 3031 pos 14: '_debugUltimatePreviousSiblingOf(after, equals: _firstChild)': is not true.
Another exception was thrown: 'package:flutter/src/rendering/object.dart': Failed assertion: line 3031 pos 14: '_debugUltimatePreviousSiblingOf(after, equals: _firstChild)': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true."><pre class="notranslate"><code class="notranslate">══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
The following assertion was thrown building NotificationListener&lt;KeepAliveNotification&gt;:
'package:flutter/src/rendering/object.dart': Failed assertion: line 3031 pos 14:
'_debugUltimatePreviousSiblingOf(after, equals: _firstChild)': is not true.
Either the assertion indicates an error in the framework itself, or we should provide substantially
more information in this error message to help you determine and fix the underlying cause.
In either case, please report this assertion by filing a bug on GitHub:
  https://github.com/flutter/flutter/issues/new
When the exception was thrown, this was the stack:
#2      RenderSliver&amp;ContainerRenderObjectMixin._insertIntoChildList (package:flutter/src/rendering/object.dart:3031:14)
#3      RenderSliver&amp;ContainerRenderObjectMixin.insert (package:flutter/src/rendering/object.dart:3065:5)
#4      RenderSliverMultiBoxAdaptor.insert (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:193:17)
#5      SliverMultiBoxAdaptorElement.insertChildRenderObject (package:flutter/src/widgets/sliver.dart:840:18)
#6      RenderObjectElement.attachRenderObject (package:flutter/src/widgets/framework.dart:4380:35)
#7      RenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4151:5)
#8      SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4515:16)
#9      Element.inflateWidget (package:flutter/src/widgets/framework.dart:2882:14)
#10     Element.updateChild (package:flutter/src/widgets/framework.dart:2685:12)
#11     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#12     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#13     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3514:5)
#14     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3509:5)
#15     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2882:14)
#16     Element.updateChild (package:flutter/src/widgets/framework.dart:2685:12)
#17     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#18     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#19     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3514:5)
#20     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3509:5)
#21     ParentDataElement.mount (package:flutter/src/widgets/framework.dart:3827:16)
#22     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2882:14)
#23     Element.updateChild (package:flutter/src/widgets/framework.dart:2685:12)
#24     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#25     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#26     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3514:5)
#27     StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3652:22)
#28     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3509:5)
#29     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2882:14)
#30     Element.updateChild (package:flutter/src/widgets/framework.dart:2685:12)
#31     SliverMultiBoxAdaptorElement.performRebuild (package:flutter/src/widgets/sliver.dart:696:34)
#32     SliverMultiBoxAdaptorElement.update (package:flutter/src/widgets/sliver.dart:665:7)
#33     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#34     RenderObjectElement.updateChildren (package:flutter/src/widgets/framework.dart:4250:32)
#35     MultiChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4631:17)
#36     _ViewportElement.update (package:flutter/src/widgets/viewport.dart:150:17)
#37     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#38     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#39     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#40     ProxyElement.update (package:flutter/src/widgets/framework.dart:3781:5)
#41     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#42     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4523:14)
#43     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#44     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4523:14)
#45     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#46     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4523:14)
#47     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#48     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#49     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#50     StatefulElement.update (package:flutter/src/widgets/framework.dart:3671:5)
#51     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#52     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#53     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#54     StatefulElement.update (package:flutter/src/widgets/framework.dart:3671:5)
#55     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#56     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#57     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#58     StatelessElement.update (package:flutter/src/widgets/framework.dart:3596:5)
#59     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#60     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#61     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#62     StatefulElement.update (package:flutter/src/widgets/framework.dart:3671:5)
#63     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#64     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#65     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#66     ProxyElement.update (package:flutter/src/widgets/framework.dart:3781:5)
#67     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#68     RenderObjectElement.updateChildren (package:flutter/src/widgets/framework.dart:4250:32)
#69     MultiChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4631:17)
#70     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#71     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#72     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#73     ProxyElement.update (package:flutter/src/widgets/framework.dart:3781:5)
#74     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#75     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#76     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#77     StatefulElement.update (package:flutter/src/widgets/framework.dart:3671:5)
#78     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#79     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4523:14)
#80     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#81     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#82     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#83     StatelessElement.update (package:flutter/src/widgets/framework.dart:3596:5)
#84     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#85     SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4523:14)
#86     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#87     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#88     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#89     StatefulElement.update (package:flutter/src/widgets/framework.dart:3671:5)
#90     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#91     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#92     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#93     StatefulElement.update (package:flutter/src/widgets/framework.dart:3671:5)
#94     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#95     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#96     Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#97     ProxyElement.update (package:flutter/src/widgets/framework.dart:3781:5)
#98     Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#99     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#100    Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#101    ProxyElement.update (package:flutter/src/widgets/framework.dart:3781:5)
#102    Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#103    ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#104    Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#105    StatefulElement.update (package:flutter/src/widgets/framework.dart:3671:5)
#106    Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#107    ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#108    Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#109    BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2260:33)
#110    BindingBase&amp;SchedulerBinding&amp;GestureBinding&amp;ServicesBinding&amp;RendererBinding&amp;WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:503:20)
#111    BindingBase&amp;SchedulerBinding&amp;GestureBinding&amp;ServicesBinding&amp;RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:189:5)
#112    BindingBase&amp;SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:695:15)
#113    BindingBase&amp;SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:643:9)
#114    _invoke (file:///b/build/slave/Mac_Engine/build/src/flutter/lib/ui/hooks.dart:86)
#115    _drawFrame (file:///b/build/slave/Mac_Engine/build/src/flutter/lib/ui/hooks.dart:75)
(elided 2 frames from class _AssertionError)
════════════════════════════════════════════════════════════════════════════════════════════════════
Another exception was thrown: 'package:flutter/src/rendering/object.dart': Failed assertion: line 3031 pos 14: '_debugUltimatePreviousSiblingOf(after, equals: _firstChild)': is not true.
Another exception was thrown: 'package:flutter/src/rendering/object.dart': Failed assertion: line 3031 pos 14: '_debugUltimatePreviousSiblingOf(after, equals: _firstChild)': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
</code></pre></div>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="Analyzing /Users/matt/code/flutter/kudos...
  lint • Don't import implementation files from another package at lib/feed.dart:5:8 • implementation_imports
  lint • Close instances of `dart.core.Sink` at lib/feed.dart:26:26 • close_sinks
  lint • Don't explicitly initialize variables to null at lib/loading_list_view.dart:23:5 • avoid_init_to_null
  lint • Don't import implementation files from another package at lib/post.dart:3:8 • implementation_imports
  hint • Unused import at lib/application.dart:4:8 • unused_import
  hint • Unused import at lib/feed.dart:2:8 • unused_import
  hint • Unused import at lib/feed.dart:5:8 • unused_import
  hint • Unused import at lib/feed.dart:7:8 • unused_import
  hint • Unused import at lib/feed.dart:12:8 • unused_import
  hint • Unused import at lib/feed.dart:13:8 • unused_import
  hint • This method overrides a method annotated as @mustCallSuper in 'State', but does not invoke the overridden method at lib/feed.dart:29:8 • must_call_super
  hint • This method overrides a method annotated as @mustCallSuper in 'State', but does not invoke the overridden method at lib/feed.dart:40:8 • must_call_super
  hint • The type parameter 'widgetAdapter' is annotated with @required but only named parameters without default value can be annotated with it at lib/loading_list_view.dart:23:5 • invalid_required_param
  hint • Unused import at lib/main.dart:6:8 • unused_import
  hint • The value of the field '_counter' isn't used at lib/main.dart:56:7 • unused_field
  hint • This method overrides a method annotated as @mustCallSuper in 'State', but does not invoke the overridden method at lib/main.dart:63:8 • must_call_super
  hint • This method overrides a method annotated as @mustCallSuper in 'State', but does not invoke the overridden method at lib/main.dart:71:8 • must_call_super
  hint • The method '_incrementCounter' isn't used at lib/main.dart:76:8 • unused_element
  hint • Unused import at lib/post.dart:7:8 • unused_import
  hint • This class inherits from a class marked as @immutable, and therefore should be immutable (all instance fields must be final) at lib/post.dart:10:7 • must_be_immutable
  hint • This class inherits from a class marked as @immutable, and therefore should be immutable (all instance fields must be final) at lib/post.dart:34:7 • must_be_immutable
  hint • The value of the local variable 'plainText' isn't used at lib/post.dart:71:10 • unused_local_variable
  hint • This class inherits from a class marked as @immutable, and therefore should be immutable (all instance fields must be final) at lib/post.dart:112:7 • must_be_immutable
  hint • This class inherits from a class marked as @immutable, and therefore should be immutable (all instance fields must be final) at lib/post.dart:160:7 • must_be_immutable
  hint • This class inherits from a class marked as @immutable, and therefore should be immutable (all instance fields must be final) at lib/profile.dart:10:7 • must_be_immutable
  hint • This method overrides a method annotated as @mustCallSuper in 'State', but does not invoke the overridden method at lib/profile.dart:27:10 • must_call_super
  hint • This class inherits from a class marked as @immutable, and therefore should be immutable (all instance fields must be final) at lib/profile.dart:145:7 • must_be_immutable
  hint • The class '_KudosEarned' isn't used at lib/profile.dart:218:7 • unused_element
  hint • Unused import at lib/send_photo.dart:5:8 • unused_import
  hint • Unused import at lib/usersearch.dart:6:8 • unused_import
  hint • Unused import at lib/usersearch.dart:7:8 • unused_import
  hint • This method overrides a method annotated as @mustCallSuper in 'State', but does not invoke the overridden method at lib/usersearch.dart:25:10 • must_call_super
32 issues found."><pre class="notranslate"><code class="notranslate">Analyzing /Users/matt/code/flutter/kudos...
  lint • Don't import implementation files from another package at lib/feed.dart:5:8 • implementation_imports
  lint • Close instances of `dart.core.Sink` at lib/feed.dart:26:26 • close_sinks
  lint • Don't explicitly initialize variables to null at lib/loading_list_view.dart:23:5 • avoid_init_to_null
  lint • Don't import implementation files from another package at lib/post.dart:3:8 • implementation_imports
  hint • Unused import at lib/application.dart:4:8 • unused_import
  hint • Unused import at lib/feed.dart:2:8 • unused_import
  hint • Unused import at lib/feed.dart:5:8 • unused_import
  hint • Unused import at lib/feed.dart:7:8 • unused_import
  hint • Unused import at lib/feed.dart:12:8 • unused_import
  hint • Unused import at lib/feed.dart:13:8 • unused_import
  hint • This method overrides a method annotated as @mustCallSuper in 'State', but does not invoke the overridden method at lib/feed.dart:29:8 • must_call_super
  hint • This method overrides a method annotated as @mustCallSuper in 'State', but does not invoke the overridden method at lib/feed.dart:40:8 • must_call_super
  hint • The type parameter 'widgetAdapter' is annotated with @required but only named parameters without default value can be annotated with it at lib/loading_list_view.dart:23:5 • invalid_required_param
  hint • Unused import at lib/main.dart:6:8 • unused_import
  hint • The value of the field '_counter' isn't used at lib/main.dart:56:7 • unused_field
  hint • This method overrides a method annotated as @mustCallSuper in 'State', but does not invoke the overridden method at lib/main.dart:63:8 • must_call_super
  hint • This method overrides a method annotated as @mustCallSuper in 'State', but does not invoke the overridden method at lib/main.dart:71:8 • must_call_super
  hint • The method '_incrementCounter' isn't used at lib/main.dart:76:8 • unused_element
  hint • Unused import at lib/post.dart:7:8 • unused_import
  hint • This class inherits from a class marked as @immutable, and therefore should be immutable (all instance fields must be final) at lib/post.dart:10:7 • must_be_immutable
  hint • This class inherits from a class marked as @immutable, and therefore should be immutable (all instance fields must be final) at lib/post.dart:34:7 • must_be_immutable
  hint • The value of the local variable 'plainText' isn't used at lib/post.dart:71:10 • unused_local_variable
  hint • This class inherits from a class marked as @immutable, and therefore should be immutable (all instance fields must be final) at lib/post.dart:112:7 • must_be_immutable
  hint • This class inherits from a class marked as @immutable, and therefore should be immutable (all instance fields must be final) at lib/post.dart:160:7 • must_be_immutable
  hint • This class inherits from a class marked as @immutable, and therefore should be immutable (all instance fields must be final) at lib/profile.dart:10:7 • must_be_immutable
  hint • This method overrides a method annotated as @mustCallSuper in 'State', but does not invoke the overridden method at lib/profile.dart:27:10 • must_call_super
  hint • This class inherits from a class marked as @immutable, and therefore should be immutable (all instance fields must be final) at lib/profile.dart:145:7 • must_be_immutable
  hint • The class '_KudosEarned' isn't used at lib/profile.dart:218:7 • unused_element
  hint • Unused import at lib/send_photo.dart:5:8 • unused_import
  hint • Unused import at lib/usersearch.dart:6:8 • unused_import
  hint • Unused import at lib/usersearch.dart:7:8 • unused_import
  hint • This method overrides a method annotated as @mustCallSuper in 'State', but does not invoke the overridden method at lib/usersearch.dart:25:10 • must_call_super
32 issues found.
</code></pre></div>
<h2 dir="auto">Flutter Doctor</h2>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="[✓] Flutter (on Mac OS X 10.12.6 16G29, locale en-US, channel alpha)
    • Flutter at /Users/matt/code/flutter/flutter
    • Framework revision b156a0f054 (3 weeks ago), 2017-08-11 22:01:40 -0700
    • Engine revision fef7d827d6
    • Tools Dart version 1.25.0-dev.9.0

[✓] Android toolchain - develop for Android devices (Android SDK 25.0.3)
    • Android SDK at /Users/matt/code/android/android
    • Platform android-25, build-tools 25.0.3
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_112-release-b06)

[✓] iOS toolchain - develop for iOS devices (Xcode 8.3.3)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 8.3.3, Build version 8E3004b
    • ios-deploy 1.9.1
    • CocoaPods version 1.3.1

[✓] Android Studio (version 2.3)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Java version OpenJDK Runtime Environment (build 1.8.0_112-release-b06)

[✓] IntelliJ IDEA Ultimate Edition (version 2017.2.2)
    • Flutter plugin version 16.0
    • Dart plugin version 172.3757.55

[✓] Connected devices
    • iPhone 6s • 3DF999CB-1CD6-4649-8187-DDEFBDB14DFA • ios • iOS 10.3 (simulator)
"><pre class="notranslate"><code class="notranslate">[✓] Flutter (on Mac OS X 10.12.6 16G29, locale en-US, channel alpha)
    • Flutter at /Users/matt/code/flutter/flutter
    • Framework revision b156a0f054 (3 weeks ago), 2017-08-11 22:01:40 -0700
    • Engine revision fef7d827d6
    • Tools Dart version 1.25.0-dev.9.0

[✓] Android toolchain - develop for Android devices (Android SDK 25.0.3)
    • Android SDK at /Users/matt/code/android/android
    • Platform android-25, build-tools 25.0.3
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_112-release-b06)

[✓] iOS toolchain - develop for iOS devices (Xcode 8.3.3)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 8.3.3, Build version 8E3004b
    • ios-deploy 1.9.1
    • CocoaPods version 1.3.1

[✓] Android Studio (version 2.3)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Java version OpenJDK Runtime Environment (build 1.8.0_112-release-b06)

[✓] IntelliJ IDEA Ultimate Edition (version 2017.2.2)
    • Flutter plugin version 16.0
    • Dart plugin version 172.3757.55

[✓] Connected devices
    • iPhone 6s • 3DF999CB-1CD6-4649-8187-DDEFBDB14DFA • ios • iOS 10.3 (simulator)

</code></pre></div>
<blockquote>
<p dir="auto">For more information about diagnosing and reporting Flutter bugs, please see <a href="https://flutter.io/bug-reports/" rel="nofollow">https://flutter.io/bug-reports/</a>.</p>
</blockquote>