Issue 1:
I wrote a simple page using PageView and AutomaticKeepAliveClientMixin, which contains 4 page, A, B, C, D, and when App starts a meeting, the user points to D first, then tap B or C， and it can't be displayed on B or C. It can be concluded that when App starts, if you click on the Tab behind, the front will not appear.

[√] Flutter (Channel unknown, v0.3.5, on Microsoft Windows [Version 10.0.16299.371], locale zh-CN)
• Flutter version 0.3.5 at D:\flutter
• Framework revision 7ffcd3d22d (11 days ago), 2018-04-24 14:03:41 -0700
• Engine revision ec611470b5
• Dart version 2.0.0-dev.48.0.flutter-fe606f890b

[√] Android toolchain - develop for Android devices (Android SDK 27.0.3)
• Android SDK at D:\android\android-sdk-windows
• Android NDK location not configured (optional; useful for native profiling support)
• Platform android-27, build-tools 27.0.3
• ANDROID_HOME = D:\android\android-sdk-windows
• Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
• Java version OpenJDK Runtime Environment (build 1.8.0_152-release-915-b01)
• All Android licenses accepted.

[√] Android Studio (version 3.0)
• Android Studio at C:\Program Files\Android\Android Studio
X Flutter plugin not installed; this adds Flutter specific functionality.
X Dart plugin not installed; this adds Dart specific functionality.
• Java version OpenJDK Runtime Environment (build 1.8.0_152-release-915-b01)

[√] IntelliJ IDEA Community Edition (version 2018.1)
• IntelliJ at C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2018.1.1
• Flutter plugin version 24.1.2
• Dart plugin version 181.4668.60

[√] VS Code, 32-bit edition (version 1.22.2)
• VS Code at C:\Program Files (x86)\Microsoft VS Code
• Dart Code extension version 2.12.1

[√] Connected devices (1 available)
• vivo Y75A • 5SUWWCDQPNZSOFSO • android-arm64 • Android 7.1.1 (API 25)

[ +150 ms] I/flutter ( 4500): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
[ +36 ms] I/flutter ( 4500): The following assertion was thrown building NotificationListener<KeepAliveNotification>:
[ +2 ms] I/flutter ( 4500): 'package:flutter/src/rendering/object.dart': Failed assertion: line 2732 pos 14:
[ +3 ms] I/flutter ( 4500): '_debugUltimatePreviousSiblingOf(after, equals: _firstChild)': is not true.
[ +481 ms] I/flutter ( 4500): Either the assertion indicates an error in the framework itself, or we should provide substantially
[ +1 ms] I/flutter ( 4500): more information in this error message to help you determine and fix the underlying cause.
[ ] I/flutter ( 4500): In either case, please report this assertion by filing a bug on GitHub:
[ +1 ms] I/flutter ( 4500): https://github.com/flutter/flutter/issues/new
[ +6 ms] I/flutter ( 4500): When the exception was thrown, this was the stack:
[ +72 ms] I/flutter ( 4500): #2 RenderSliver&ContainerRenderObjectMixin._insertIntoChildList (package:flutter/src/rendering/object.dart:2732:14)
[ +2 ms] I/flutter ( 4500): #3 RenderSliver&ContainerRenderObjectMixin.insert (package:flutter/src/rendering/object.dart:2766:5)
[ ] I/flutter ( 4500): #4 RenderSliverMultiBoxAdaptor.insert (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:209:17)
[ ] I/flutter ( 4500): #5 SliverMultiBoxAdaptorElement.insertChildRenderObject (package:flutter/src/widgets/sliver.dart:863:18)
[ +1 ms] I/flutter ( 4500): #6 RenderObjectElement.attachRenderObject (package:flutter/src/widgets/framework.dart:4505:35)
[ ] I/flutter ( 4500): #7 RenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4271:5)
[ ] I/flutter ( 4500): #8 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4645:16)
[ +1 ms] I/flutter ( 4500): #9 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2899:14)
[ +2 ms] I/flutter ( 4500): #10 Element.updateChild (package:flutter/src/widgets/framework.dart:2702:12)
[ ] I/flutter ( 4500): #11 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3645:16)
[ +1 ms] I/flutter ( 4500): #12 Element.rebuild (package:flutter/src/widgets/framework.dart:3487:5)
[ +4 ms] I/flutter ( 4500): #13 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3614:5)
[ +2 ms] I/flutter ( 4500): #14 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3609:5)
[ ] I/flutter ( 4500): #15 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2899:14)
[ ] I/flutter ( 4500): #16 Element.updateChild (package:flutter/src/widgets/framework.dart:2702:12)
[ +2 ms] I/flutter ( 4500): #17 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3645:16)
[ ] I/flutter ( 4500): #18 Element.rebuild (package:flutter/src/widgets/framework.dart:3487:5)
[ ] I/flutter ( 4500): #19 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3614:5)
[ +2 ms] I/flutter ( 4500): #20 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3609:5)
[ ] I/flutter ( 4500): #21 ParentDataElement.mount (package:flutter/src/widgets/framework.dart:3947:16)
[ ] I/flutter ( 4500): #22 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2899:14)
[ +2 ms] I/flutter ( 4500): #23 Element.updateChild (package:flutter/src/widgets/framework.dart:2702:12)
[ +3 ms] I/flutter ( 4500): #24 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3645:16)
[ ] I/flutter ( 4500): #25 Element.rebuild (package:flutter/src/widgets/framework.dart:3487:5)
[ ] I/flutter ( 4500): #26 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3614:5)
[ +2 ms] I/flutter ( 4500): #27 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3761:22)
[ ] I/flutter ( 4500): #28 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3609:5)
[ ] I/flutter ( 4500): #29 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2899:14)
[ +2 ms] I/flutter ( 4500): #30 Element.updateChild (package:flutter/src/widgets/framework.dart:2702:12)
[ ] I/flutter ( 4500): #31 SliverMultiBoxAdaptorElement.updateChild (package:flutter/src/widgets/sliver.dart:744:47)
[ ] I/flutter ( 4500): #32 SliverMultiBoxAdaptorElement.performRebuild (package:flutter/src/widgets/sliver.dart:702:34)
[ +2 ms] I/flutter ( 4500): #33 SliverMultiBoxAdaptorElement.update (package:flutter/src/widgets/sliver.dart:671:7)
[ ] I/flutter ( 4500): #34 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ ] I/flutter ( 4500): #35 RenderObjectElement.updateChildren (package:flutter/src/widgets/framework.dart:4371:32)
[ +1 ms] I/flutter ( 4500): #36 MultiChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4761:17)
[ ] I/flutter ( 4500): #37 _ViewportElement.update (package:flutter/src/widgets/viewport.dart:187:17)
[ ] I/flutter ( 4500): #38 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ +1 ms] I/flutter ( 4500): #39 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3645:16)
[ ] I/flutter ( 4500): #40 Element.rebuild (package:flutter/src/widgets/framework.dart:3487:5)
[ +1 ms] I/flutter ( 4500): #41 ProxyElement.update (package:flutter/src/widgets/framework.dart:3901:5)
[ ] I/flutter ( 4500): #42 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ ] I/flutter ( 4500): #43 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4653:14)
[ +2 ms] I/flutter ( 4500): #44 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ ] I/flutter ( 4500): #45 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4653:14)
[ ] I/flutter ( 4500): #46 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ +4 ms] I/flutter ( 4500): #47 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4653:14)
[ ] I/flutter ( 4500): #48 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ ] I/flutter ( 4500): #49 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4653:14)
[ +1 ms] I/flutter ( 4500): #50 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ ] I/flutter ( 4500): #51 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3645:16)
[ ] I/flutter ( 4500): #52 Element.rebuild (package:flutter/src/widgets/framework.dart:3487:5)
[ +2 ms] I/flutter ( 4500): #53 StatefulElement.update (package:flutter/src/widgets/framework.dart:3791:5)
[ ] I/flutter ( 4500): #54 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ ] I/flutter ( 4500): #55 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4653:14)
[ ] I/flutter ( 4500): #56 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ +1 ms] I/flutter ( 4500): #57 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3645:16)
[ ] I/flutter ( 4500): #58 Element.rebuild (package:flutter/src/widgets/framework.dart:3487:5)
[ ] I/flutter ( 4500): #59 StatefulElement.update (package:flutter/src/widgets/framework.dart:3791:5)
[ ] I/flutter ( 4500): #60 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ +2 ms] I/flutter ( 4500): #61 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3645:16)
[ ] I/flutter ( 4500): #62 Element.rebuild (package:flutter/src/widgets/framework.dart:3487:5)
[ ] I/flutter ( 4500): #63 StatelessElement.update (package:flutter/src/widgets/framework.dart:3694:5)
[ ] I/flutter ( 4500): #64 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ +1 ms] I/flutter ( 4500): #65 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3645:16)
[ ] I/flutter ( 4500): #66 Element.rebuild (package:flutter/src/widgets/framework.dart:3487:5)
[ ] I/flutter ( 4500): #67 StatefulElement.update (package:flutter/src/widgets/framework.dart:3791:5)
[ ] I/flutter ( 4500): #68 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ ] I/flutter ( 4500): #69 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3645:16)
[ +1 ms] I/flutter ( 4500): #70 Element.rebuild (package:flutter/src/widgets/framework.dart:3487:5)
[ +1 ms] I/flutter ( 4500): #71 ProxyElement.update (package:flutter/src/widgets/framework.dart:3901:5)
[ ] I/flutter ( 4500): #72 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ +2 ms] I/flutter ( 4500): #73 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3645:16)
[ +1 ms] I/flutter ( 4500): #74 Element.rebuild (package:flutter/src/widgets/framework.dart:3487:5)
[ ] I/flutter ( 4500): #75 ProxyElement.update (package:flutter/src/widgets/framework.dart:3901:5)
[ ] I/flutter ( 4500): #76 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ +3 ms] I/flutter ( 4500): #77 RenderObjectElement.updateChildren (package:flutter/src/widgets/framework.dart:4371:32)
[ ] I/flutter ( 4500): #78 MultiChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4761:17)
[ ] I/flutter ( 4500): #79 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ ] I/flutter ( 4500): #80 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3645:16)
[ ] I/flutter ( 4500): #81 Element.rebuild (package:flutter/src/widgets/framework.dart:3487:5)
[ ] I/flutter ( 4500): #82 StatefulElement.update (package:flutter/src/widgets/framework.dart:3791:5)
[ +1 ms] I/flutter ( 4500): #83 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ ] I/flutter ( 4500): #84 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3645:16)
[ ] I/flutter ( 4500): #85 Element.rebuild (package:flutter/src/widgets/framework.dart:3487:5)
[ ] I/flutter ( 4500): #86 ProxyElement.update (package:flutter/src/widgets/framework.dart:3901:5)
[ ] I/flutter ( 4500): #87 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ ] I/flutter ( 4500): #88 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3645:16)
[ ] I/flutter ( 4500): #89 Element.rebuild (package:flutter/src/widgets/framework.dart:3487:5)
[ +1 ms] I/flutter ( 4500): #90 StatefulElement.update (package:flutter/src/widgets/framework.dart:3791:5)
[ ] I/flutter ( 4500): #91 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ ] I/flutter ( 4500): #92 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4653:14)
[ ] I/flutter ( 4500): #93 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ ] I/flutter ( 4500): #94 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3645:16)
[ ] I/flutter ( 4500): #95 Element.rebuild (package:flutter/src/widgets/framework.dart:3487:5)
[ +1 ms] I/flutter ( 4500): #96 StatelessElement.update (package:flutter/src/widgets/framework.dart:3694:5)
[ ] I/flutter ( 4500): #97 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ ] I/flutter ( 4500): #98 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4653:14)
[ ] I/flutter ( 4500): #99 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ +1 ms] I/flutter ( 4500): #100 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3645:16)
[ ] I/flutter ( 4500): #101 Element.rebuild (package:flutter/src/widgets/framework.dart:3487:5)
[ +1 ms] I/flutter ( 4500): #102 StatefulElement.update (package:flutter/src/widgets/framework.dart:3791:5)
[ ] I/flutter ( 4500): #103 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ ] I/flutter ( 4500): #104 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3645:16)
[ +7 ms] I/flutter ( 4500): #105 Element.rebuild (package:flutter/src/widgets/framework.dart:3487:5)
[ +2 ms] I/flutter ( 4500): #106 StatefulElement.update (package:flutter/src/widgets/framework.dart:3791:5)
[ ] I/flutter ( 4500): #107 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ +2 ms] I/flutter ( 4500): #108 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3645:16)
[ +2 ms] I/flutter ( 4500): #109 Element.rebuild (package:flutter/src/widgets/framework.dart:3487:5)
[ +1 ms] I/flutter ( 4500): #110 ProxyElement.update (package:flutter/src/widgets/framework.dart:3901:5)
[ ] I/flutter ( 4500): #111 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ +2 ms] I/flutter ( 4500): #112 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3645:16)
[ ] I/flutter ( 4500): #113 Element.rebuild (package:flutter/src/widgets/framework.dart:3487:5)
[ ] I/flutter ( 4500): #114 ProxyElement.update (package:flutter/src/widgets/framework.dart:3901:5)
[ ] I/flutter ( 4500): #115 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ +1 ms] I/flutter ( 4500): #116 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3645:16)
[ ] I/flutter ( 4500): #117 Element.rebuild (package:flutter/src/widgets/framework.dart:3487:5)
[ +3 ms] I/flutter ( 4500): #118 StatefulElement.update (package:flutter/src/widgets/framework.dart:3791:5)
[ ] I/flutter ( 4500): #119 Element.updateChild (package:flutter/src/widgets/framework.dart:2691:15)
[ ] I/flutter ( 4500): #120 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3645:16)
[ ] I/flutter ( 4500): #121 Element.rebuild (package:flutter/src/widgets/framework.dart:3487:5)
[ ] I/flutter ( 4500): #122 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2234:33)
[ ] I/flutter ( 4500): #123 BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&RendererBinding&WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:626:20)
[ ] I/flutter ( 4500): #124 BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:208:5)
[ ] I/flutter ( 4500): #125 BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:990:15)
[ ] I/flutter ( 4500): #126 BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:930:9)
[ ] I/flutter ( 4500): #127 BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:842:5)
[ ] I/flutter ( 4500): #128 _invoke (file:///b/build/slave/Linux_Engine/build/src/flutter/lib/ui/hooks.dart:120)
[ ] I/flutter ( 4500): #129 _drawFrame (file:///b/build/slave/Linux_Engine/build/src/flutter/lib/ui/hooks.dart:109)

import 'package:flutter/material.dart';

void main() => runApp(new MyApp());

class TabItem {
const TabItem({this.title, this.icon});
final String title;
final IconData icon;
}

const List<TabItem> tabItems = const <TabItem>[
const TabItem(title: 'A', icon: Icons.pages),
const TabItem(title: 'B', icon: Icons.pages),
const TabItem(title: 'C', icon: Icons.pages),
const TabItem(title: 'D', icon: Icons.pages),
];

class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'Flutter Demo',
theme: new ThemeData(
primarySwatch: Colors.blue,
),
home: new MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}

class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;

@override
_MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
PageController _tabController;
int _getIndex(){
return this._tabController.hasClients ? this._tabController.page.toInt() : 0;
}

@override
void initState() {
super.initState();
this._tabController = new PageController(keepPage: true);
this._tabController.addListener(this._onTabIndexChanged);
}

@override
void dispose() {
this._tabController.removeListener(this._onTabIndexChanged);
this._tabController.dispose();
super.dispose();
}

void _onTabItemClick(int index){
this._goPage(index);
}

void _goPage(int index){
this._tabController.jumpToPage(index);
}

void _onTabIndexChanged(){
setState((){

});
}

@override
Widget build(BuildContext context) {
int page = this._getIndex();
return new Scaffold(
appBar: new AppBar(
title: new Text(widget.title),
),
bottomNavigationBar: new BottomNavigationBar(
items: tabItems.map((TabItem item) {
return new BottomNavigationBarItem(
title: new Text(item.title),
icon: new Icon(item.icon),
);
}).toList(),
onTap: this._onTabItemClick,
currentIndex: page,
type: BottomNavigationBarType.fixed,
),
body: new PageView(
physics: const NeverScrollableScrollPhysics(),
controller: this._tabController,
children: <Widget>[
new PageA(),
new PageB(),
new PageC(),
new PageD(),
],
)

);
}
}

class PageA extends StatefulWidget {
PageA({Key key}) : super(key: key);

@override
_PageAState createState() => new _PageAState();
}

class _PageAState extends State<PageA> with AutomaticKeepAliveClientMixin<PageA> {
@override
bool get wantKeepAlive{
return true;
}
@override
Widget build(BuildContext context) {
super.build(context);
return new Center(
child: new Text("A"),
);
}
}

class PageB extends StatefulWidget {
PageB({Key key}) : super(key: key);

@override
_PageBState createState() => new _PageBState();
}

class _PageBState extends State<PageB> with AutomaticKeepAliveClientMixin<PageB> {
@override
bool get wantKeepAlive{
return true;
}
@override
Widget build(BuildContext context) {
super.build(context);
return new Center(
child: new Text("B"),
);
}
}

class PageC extends StatefulWidget {
PageC({Key key}) : super(key: key);

@override
_PageCState createState() => new _PageCState();
}

class _PageCState extends State<PageC> with AutomaticKeepAliveClientMixin<PageC> {
@override
bool get wantKeepAlive{
return true;
}
@override
Widget build(BuildContext context) {
super.build(context);
return new Center(
child: new Text("C"),
);
}
}

class PageD extends StatefulWidget {
PageD({Key key}) : super(key: key);

@override
_PageDState createState() => new _PageDState();
}

class _PageDState extends State<PageD> with AutomaticKeepAliveClientMixin<PageD> {
@override
bool get wantKeepAlive{
return true;
}
@override
Widget build(BuildContext context) {
super.build(context);
return new Center(
child: new Text("D"),
);
}
}

Issue 2:
Steps to Reproduce

I have a PageView that contains the top level widgets for my app, with switching between them controlled by a BottomNavBar. As per @Hixie's advice in the chat, I am adding AutomaticKeepAliveClientMixin 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.

Logs

══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
The following assertion was thrown building NotificationListener<KeepAliveNotification>:
'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&ContainerRenderObjectMixin._insertIntoChildList (package:flutter/src/rendering/object.dart:3031:14)
#3 RenderSliver&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&SchedulerBinding&GestureBinding&ServicesBinding&RendererBinding&WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:503:20)
#111 BindingBase&SchedulerBinding&GestureBinding&ServicesBinding&RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:189:5)
#112 BindingBase&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:695:15)
#113 BindingBase&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.

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.

Flutter Doctor

[✓] 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)

For more information about diagnosing and reporting Flutter bugs, please see https://flutter.io/bug-reports/.