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Null Reference Exception thrown when updating views

See original GitHub issue

Original issue: #518

While updating the UI when switching between 2 different contents (Label -> ListView), the app throws a NullReferenceException (coming from Xamarin.Forms) but only on some Android devices.

Affected platforms: Android
Affected build mode: Debug, Release
Affected devices:
- Xiaomi Mi 8
- Samsung S8
Unaffected devices:
- Emulators
- Xiaomi Redmi Note 7
- LG G6
- Google Nexus 5
- Sony Xperia
- Motorola G6
- Xiaomi Redmi 4X
- Nokia 8

Stack trace

Stack trace for Repro 1

Unable to update view:: System.NullReferenceException: Object reference not set to an instance of an object.
at Xamarin.Forms.Platform.Android.PageRenderer.Xamarin.Forms.Platform.Android.IOrderedTraversalController.UpdateTraversalOrder () [0x000a4] in D:\a\1\s\Xamarin.Forms.Platform.Android\Renderers\PageRenderer.cs:177
at Xamarin.Forms.Platform.Android.VisualElementRenderer1[TElement].UpdateParentPageTraversalOrder () [0x00025] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:404 at Xamarin.Forms.Platform.Android.VisualElementRenderer1[TElement].OnElementPropertyChanged (System.Object sender, System.ComponentModel.PropertyChangedEventArgs e) [0x00116] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:369
at (wrapper delegate-invoke) .invoke_void_object_PropertyChangedEventArgs(object,System.ComponentModel.PropertyChangedEventArgs)
at Xamarin.Forms.BindableObject.OnPropertyChanged (System.String propertyName) [0x00000] in D:\a\1\s\Xamarin.Forms.Core
BindableObject.cs:211
at Xamarin.Forms.Element.OnPropertyChanged (System.String propertyName) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\Element.cs:353
at Xamarin.Forms.Element.set_Parent (Xamarin.Forms.Element value) [0x00094] in D:\a\1\s\Xamarin.Forms.Core\Element.cs:210
at Xamarin.Forms.Element.OnChildRemoved (Xamarin.Forms.Element child) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\Element.cs:335
at Xamarin.Forms.VisualElement.OnChildRemoved (Xamarin.Forms.Element child) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\VisualElement.cs:750
at Xamarin.Forms.Layout1[T].OnChildRemoved (Xamarin.Forms.Element child) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\Layout.cs:41 at Xamarin.Forms.Layout.OnInternalRemoved (Xamarin.Forms.View view) [0x00012] in D:\a\1\s\Xamarin.Forms.Core\Layout.cs:464 at Xamarin.Forms.Layout.InternalChildrenOnCollectionChanged (System.Object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e) [0x0002b] in D:\a\1\s\Xamarin.Forms.Core\Layout.cs:427 at (wrap per delegate-invoke) <Module>.invoke_void_object_NotifyCollectionChangedEventArgs(object,System.Collections.Specialized.NotifyCollectionChangedEventArgs) at System.Collections.ObjectModel.ObservableCollection1[T].OnCollectionChanged (System.Collections.Specialized.NotifyCollectionChangedEventArgs e) [0x00018] in /Users/builder/jenkins/workspace/xamarin-android-d16-1/xamarin-android/external/mono/external/corefx/src/System.ObjectModel/src/System/Collections/ObjectModel/ObservableCollection.cs:263
at System.Collections.ObjectModel.ObservableCollection1[T].OnCollectionChanged (System.Collections.Specialized.NotifyCollectionChangedAction action, System.Object oldItem, System.Object newItem, System.Int32 index) [0x00000] in /Users/builder/jenkins/workspace/xamarin-android-d16-1/xamarin-android/external/mono/external/corefx/src/System.ObjectModel/src/System/Collections/ObjectModel/ObservableCollection.cs:354 at System.Collections.ObjectModel.ObservableCollection1[T].SetItem (System.Int32 index, T item) [
0x0001c] in /Users/builder/jenkins/workspace/xamarin-android-d16-1/xamarin-android/external/mono/external/corefx/src/System.ObjectModel/src/System/Collections/ObjectModel/ObservableCollection.cs:210
at System.Collections.ObjectModel.Collection1[T].set_Item (System.Int32 index, T value) [0x0002b] in /Users/builder/jenkins/workspace/xamarin-android-d16-1/xamarin-android/external/mono/external/corefx/src/Common/src/CoreLib/System/Collections/ObjectModel/Collection.cs:61 at Xamarin.Forms.ObservableWrapper2[TTrack,TRestrict].set_Item (System.Int32 index, TRestrict value) [0x00029] in D:\a\1\s\Xamarin.Forms.Core\ObservableWrapper.cs:140
at Fabulous.DynamicViews.Converters.updateCollectionGeneric$cont@387[T,TargetT] (Microsoft.FSharp.Core.FSharpValueOption1[T] prevCollOpt, System.Collections.Generic.IList1[T] targetColl, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] create, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] attach, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] canReuse, Microsoft.FSharp.Core .FSharpFunc2[T,TResult] update, T[] coll, Microsoft.FSharp.Core.Unit unitVar) [0x000ec] in /Git/Github/Fabulous/src/Fabulous.Core/ViewConverters.fs:407
at Fabulous.DynamicViews.Converters.updateCollectionGeneric[T,TargetT] (Microsoft.FSharp.Core.FSharpValueOption1[T] prevCollOpt, Microsoft.FSharp.Core.FSharpValueOption1[T] collOpt, System.Collections.Generic.IList1[T] targetColl, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] create, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] attach, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] canReuse, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] update) [0x00060] in /Git/Github/Fabulous/src/Fabulous.Core/ViewConverters.fs:383 at Fabulous.DynamicViews.ViewBuilders.UpdateGrid (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.Grid target) [0x00465] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms.Core.fs:5320
at <StartupCode$Fabulous-Core>.$Xamarin.Forms.Core+get_UpdateFuncGrid@5258.Invoke (Mic
rosoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.Grid target) [0x00000] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms.Core.fs:5258 at Fabulous.DynamicViews.Converters.updateCollectionGeneric$cont@387[T,TargetT] (Microsoft.FSharp.Core.FSharpValueOption1[T] prevCollOpt, System.Collections.Generic.IList1[T] targetColl, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] create, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] attach, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] canReuse, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] update, T[] coll, Microsoft.FSharp.Core.Unit unitVar) [0x0010e] in /Git/Github/Fabulous/src/Fabulous.Core/ViewConverters.fs:411 at Fabulous.DynamicViews.Converters.updateCollectionGeneric[T,TargetT] (Microsoft.FSharp.Core.FSharpValueOption1[T] prevCollOpt, Microsoft.FSharp.Core.FSharpValueOption1[T] collOpt, System.Collections.Generic.IList1[T] targetColl, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] create, Micros oft.FSharp.Core.FSharpFunc2[T,TResult] attach, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] canReuse, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] update) [0x00060] in /Git/Github/Fabulous/src/Fabulous.Core/ViewConverters.fs:383
at Fabulous.DynamicViews.ViewBuilders.UpdateGrid (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.Grid target) [0x00465] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms.Core.fs:5320 at <StartupCode$Fabulous-Core>.$Xamarin.Forms.Core+get_UpdateFuncGrid@5258.Invoke (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.Grid target) [0x00000] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms.Core.fs:5258
at Fabulous.DynamicViews.ViewBuilders.UpdateContentView (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.ContentView target) [0x001c6] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms .Core.fs:6565 at <StartupCode$Fabulous-Core>.$Xamarin.Forms.Core+get_UpdateFuncContentView@6543.Invoke (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.ContentView target) [0x00000] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms.Core.fs:6543
at Fabulous.DynamicViews.Converters.updateCollectionGeneric$cont@387[T,TargetT] (Microsoft.FSharp.Core.FSharpValueOption1[T] prevCollOpt, System.Collections.Generic.IList1[T] targetColl, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] create, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] attach, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] canReuse, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] update, T[] coll, Microsoft.FSharp.Core.Unit unitVar) [0x0010e] in /Git/Github/Fabulous/src/Fabulous.Core/ViewConverters.fs:411
at Fabulous.DynamicViews.Converters.updateCollectionGeneric[T,TargetT] (Microsoft.FSharp.Core.FSharpValueOption1[T] prevCollOpt, Microsoft.FSharp.Core.FSharpValueOption1[T] co
llOpt, System.Collections.Generic.IList1[T] targetColl, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] create, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] attach, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] canReuse, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] update) [0x00060] in /Git/Github/Fabulous/src/Fabulous.Core/ViewConverters.fs:383 at Fabulous.DynamicViews.ViewBuilders.UpdateGrid (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.Grid target) [0x00465] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms.Core.fs:5320
at <StartupCode$Fabulous-Core>.$Xamarin.Forms.Core+get_UpdateFuncGrid@5258.Invoke (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.Grid target) [0x00000] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms.Core.fs:5258 at Fabulous.DynamicViews.ViewBuilders.UpdateContentPage (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.
ViewElement curr, Xamarin.Forms.ContentPage target) [0x00239] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms.Core.fs:12613
at <StartupCode$Fabulous-Core>.$Xamarin.Forms.Core+get_UpdateFuncContentPage@12585.Invoke (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.ContentPage target) [0x00000] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms.Core.fs:12585 at Fabulous.DynamicViews.Converters.updateNavigationPages (Microsoft.FSharp.Core.FSharpValueOption1[T] prevCollOpt, Microsoft.FSharp.Core.FSharpValueOption1[T] collOpt, Xamarin.Forms.NavigationPage target, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] attach) [0x00274] in /Git/Github/Fabulous/src/Fabulous.Core/ViewConverters.fs:694
at Fabulous.DynamicViews.ViewBuilders.UpdateNavigationPage (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.NavigationPage target) [0x00339] in /Git/Github/Fabulous/src/Fabulous.Core/Xamar in.Forms.Core.fs:11975 at <StartupCode$Fabulous-Core>.$Xamarin.Forms.Core+get_UpdateFuncNavigationPage@11927.Invoke (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.NavigationPage target) [0x00000] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms.Core.fs:11927
at Fabulous.Core.ProgramRunner2[model,msg].updateView (model updatedModel) [0x00067] in /Git/Github/Fabulous/src/Fabulous.Core/ElmishProgram.fs:92 at Fabulous.Core.ProgramRunner2[model,msg].processMsg (msg msg) [0x0002e] in /Git/Github/Fabulous/src/Fabulous.Core/ElmishProgram.fs:68
07-12 16:56:22.842 I/mono-stdout(31427): Unable to update view:: System.NullReferenceException: Object reference not set to an instance of an object.
07-12 16:56:22.842 I/mono-stdout(31427): at Xamarin.Forms.Platform.Android.PageRenderer.Xamarin.Forms.Platform.Android.IOrderedTraversalController.UpdateTraversalOrder () [0x000a4] in D:\a\1\s\Xamarin.Forms.Platform.Android\Renderers\PageRenderer.cs:177
07-12 16:56:22.842 I/mono-stdout(31427): at Xamarin.Forms.Platform.Android.VisualElementRenderer1[TElement].UpdateParentPageTraversalOrder () [0x00025] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:404 07-12 16:56:22.842 I/mono-stdout(31427): at Xamarin.Forms.Platform.Android.VisualElementRenderer1[TElement].OnElementPropertyChanged (System.Object sender, System.ComponentModel.PropertyChangedEventArgs e) [0x00116] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:369
07-12 16:56:22.842 I/mono-stdout(31427): at (wrapper delegate-invoke) .invoke_void_object_PropertyChangedEventArgs(object,System.ComponentModel.PropertyChangedEventArgs)
07-12 16:56:22.842 I/mono-stdout(31427): at Xamarin.Forms.BindableObject.OnPropertyChanged (System.String propertyName) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\BindableObject.cs:211
07-12 16:56:22.842 I/mono-stdout(31427): at Xamarin.Forms.Element.OnPropertyChanged (System.String propertyName) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\Element.cs:353
07-12 16:56:22.842 I/mono-stdout(31427): at Xamarin.Forms.Element.set_Parent (Xamarin.Forms.Element value) [0x00094] in D:\a\1\s\Xamarin.Forms.Core\Element.cs:210
07-12 16:56:22.842 I/mono-stdout(31427): at Xamarin.Forms.Element.OnChildRemoved (Xamarin.Forms.Element child) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\Element.cs:335
07-12 16:56:22.842 I/mono-stdout(31427): at Xamarin.Forms.VisualElement.OnChildRemoved (Xamarin.Forms.Element child) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\VisualElement.cs:750
07-12 16:56:22.842 I/mono-stdout(31427): at Xamarin.Forms.Layout1[T].OnChildRemoved (Xamarin.Forms.Element child) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\Layout.cs:41 07-12 16:56:22.842 I/mono-stdout(31427): at Xamarin.Forms.Layout.OnInternalRemoved (Xamarin.Forms.View view) [0x00012] in D:\a\1\s\Xamarin.Forms.Core\Layout.cs:464 07-12 16:56:22.842 I/mono-stdout(31427): at Xamarin.Forms.Layout.InternalChildrenOnCollectionChanged (System.Object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e) [0x0002b] in D:\a\1\s\Xamarin.Forms.Core\Layout.cs:427 07-12 16:56:22.842 I/mono-stdout(31427): at (wrapper delegate-invoke) <Module>.invoke_void_object_NotifyCollectionChangedEventArgs(object,System.Collections.Specialized.NotifyCollectionChangedEventArgs) 07-12 16:56:22.842 I/mono-stdout(31427): at System.Collections.ObjectModel.ObservableCollection1[T].OnCollectionChanged (System.Collections.Specialized.NotifyCollectionChangedEventArgs e) [0x00018] in /Users/builder/jenkins/workspace/xamarin-android-d16-1/xamarin-android/external/mono/external/corefx/src/System.ObjectModel/src/System/Collections/ObjectModel/ObservableCollection.cs:263
07-12 16:56:22.842 I/mono-stdout(31427): at System.Collections.ObjectModel.ObservableCollection1[T].OnCollectionChanged (System.Collections.Specialized.NotifyCollectionChangedAction action, System.Object oldItem, System.Object newItem, System.Int32 index) [0x00000] in /Users/builder/jenkins/workspace/xamarin-android-d16-1/xamarin-android/external/mono/external/corefx/src/System.ObjectModel/src/System/Collections/ObjectModel/ObservableCollection.cs:354 07-12 16:56:22.842 I/mono-stdout(31427): at System.Collections.ObjectModel.ObservableCollection1[T].SetItem (System.Int32 index, T item) [0x0001c] in /Users/builder/jenkins/workspace/xamarin-android-d16-1/xamarin-android/external/mono/external/corefx/src/System.ObjectModel/src/System/Collections/ObjectModel/ObservableCollection.cs:210
07-12 16:56:22.842 I/mono-stdout(31427): at System.Collections.ObjectModel.Collection1[T].set_Item (System.Int32 index, T value) [0x0002b] in /Users/builder/jenkins/workspace/xamarin-android-d16-1/xamarin-android/external/mono/external/corefx/src/Common/src/CoreLib/System/Collections/ObjectModel/Collection.cs:61 07-12 16:56:22.842 I/mono-stdout(31427): at Xamarin.Forms.ObservableWrapper2[TTrack,TRestrict].set_Item (System.Int32 index, TRestrict value) [0x00029] in D:\a\1\s\Xamarin.Forms.Core\ObservableWrapper.cs:140
07-12 16:56:22.843 I/mono-stdout(31427): at Fabulous.DynamicViews.Converters.updateCollectionGeneric$cont@387[T,TargetT] (Microsoft.FSharp.Core.FSharpValueOption1[T] prevCollOpt, System.Collections.Generic.IList1[T] targetColl, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] create, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] attach, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] canReuse, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] update, T[] coll, Microsoft.FSharp.Core.Unit unitVar) [0x000ec] in /Git/Github/Fabulous/src/Fabulous.Core/ViewConverters.fs:407
07-12 16:56:22.843 I/mono-stdout(31427): at Fabulous.DynamicViews.Converters.updateCollectionGeneric[T,TargetT] (Microsoft.FSharp.Core.FSharpValueOption1[T] prevCollOpt, Microsoft.FSharp.Core.FSharpValueOption1[T] collOpt, System.Collections.Generic.IList1[T] targetColl, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] create, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] attach, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] canReuse, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] update) [0x00060] in /Git/Github/Fabulous/src/Fabulous.Core/ViewConverters.fs:383 07-12 16:56:22.843 I/mono-stdout(31427): at Fabulous.DynamicViews.ViewBuilders.UpdateGrid (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.Grid target) [0x00465] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms.Core.fs:5320
07-12 16:56:22.843 I/mono-stdout(31427): at <StartupCode$Fabulous-Core>.$Xamarin.Forms.Core+get_UpdateFuncGrid@5258.Invoke (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.Grid target) [0x00000] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms.Core.fs:5258 07-12 16:56:22.843 I/mono-stdout(31427): at Fabulous.DynamicViews.Converters.updateCollectionGeneric$cont@387[T,TargetT] (Microsoft.FSharp.Core.FSharpValueOption1[T] prevCollOpt, System.Collections.Generic.IList1[T] targetColl, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] create, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] attach, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] canReuse, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] update, T[] coll, Microsoft.FSharp.Core.Unit unitVar) [0x0010e] in /Git/Github/Fabulous/src/Fabulous.Core/ViewConverters.fs:411 07-12 16:56:22.843 I/mono-stdout(31427): at Fabulous.DynamicViews.Converters.updateCollectionGeneric[T,TargetT] (Microsoft.FSharp.Core.FSharpValueOption1[T] prevCollOpt, Microsoft.FSharp.Core.FSharpValueOption1[T] collOpt, System.Collections.Generic.IList1[T] targetColl, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] create, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] attach, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] canReuse, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] update) [0x00060] in /Git/Github/Fabulous/src/Fabulous.Core/ViewConverters.fs:383
07-12 16:56:22.843 I/mono-stdout(31427): at Fabulous.DynamicViews.ViewBuilders.UpdateGrid (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.Grid target) [0x00465] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms.Core.fs:5320 07-12 16:56:22.843 I/mono-stdout(31427): at <StartupCode$Fabulous-Core>.$Xamarin.Forms.Core+get_UpdateFuncGrid@5258.Invoke (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.Grid target) [0x00000] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms.Core.fs:5258
07-12 16:56:22.843 I/mono-stdout(31427): at Fabulous.DynamicViews.ViewBuilders.UpdateContentView (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.ContentView target) [0x001c6] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms.Core.fs:6565 07-12 16:56:22.843 I/mono-stdout(31427): at <StartupCode$Fabulous-Core>.$Xamarin.Forms.Core+get_UpdateFuncContentView@6543.Invoke (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.ContentView target) [0x00000] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms.Core.fs:6543
07-12 16:56:22.843 I/mono-stdout(31427): at Fabulous.DynamicViews.Converters.updateCollectionGeneric$cont@387[T,TargetT] (Microsoft.FSharp.Core.FSharpValueOption1[T] prevCollOpt, System.Collections.Generic.IList1[T] targetColl, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] create, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] attach, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] canReuse, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] update, T[] coll, Microsoft.FSharp.Core.Unit unitVar) [0x0010e] in /Git/Github/Fabulous/src/Fabulous.Core/ViewConverters.fs:411
07-12 16:56:22.843 I/mono-stdout(31427): at Fabulous.DynamicViews.Converters.updateCollectionGeneric[T,TargetT] (Microsoft.FSharp.Core.FSharpValueOption1[T] prevCollOpt, Microsoft.FSharp.Core.FSharpValueOption1[T] collOpt, System.Collections.Generic.IList1[T] targetColl, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] create, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] attach, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] canReuse, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] update) [0x00060] in /Git/Github/Fabulous/src/Fabulous.Core/ViewConverters.fs:383 07-12 16:56:22.843 I/mono-stdout(31427): at Fabulous.DynamicViews.ViewBuilders.UpdateGrid (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.Grid target) [0x00465] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms.Core.fs:5320
07-12 16:56:22.843 I/mono-stdout(31427): at <StartupCode$Fabulous-Core>.$Xamarin.Forms.Core+get_UpdateFuncGrid@5258.Invoke (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.Grid target) [0x00000] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms.Core.fs:5258 07-12 16:56:22.843 I/mono-stdout(31427): at Fabulous.DynamicViews.ViewBuilders.UpdateContentPage (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.ContentPage target) [0x00239] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms.Core.fs:12613
07-12 16:56:22.843 I/mono-stdout(31427): at <StartupCode$Fabulous-Core>.$Xamarin.Forms.Core+get_UpdateFuncContentPage@12585.Invoke (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.ContentPage target) [0x00000] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms.Core.fs:12585 07-12 16:56:22.843 I/mono-stdout(31427): at Fabulous.DynamicViews.Converters.updateNavigationPages (Microsoft.FSharp.Core.FSharpValueOption1[T] prevCollOpt, Microsoft.FSharp.Core.FSharpValueOption1[T] collOpt, Xamarin.Forms.NavigationPage target, Microsoft.FSharp.Core.FSharpFunc2[T,TResult] attach) [0x00274] in /Git/Github/Fabulous/src/Fabulous.Core/ViewConverters.fs:694
07-12 16:56:22.843 I/mono-stdout(31427): at Fabulous.DynamicViews.ViewBuilders.UpdateNavigationPage (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.NavigationPage target) [0x00339] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms.Core.fs:11975 07-12 16:56:22.843 I/mono-stdout(31427): at <StartupCode$Fabulous-Core>.$Xamarin.Forms.Core+get_UpdateFuncNavigationPage@11927.Invoke (Microsoft.FSharp.Core.FSharpValueOption1[T] prevOpt, Fabulous.DynamicViews.ViewElement curr, Xamarin.Forms.NavigationPage target) [0x00000] in /Git/Github/Fabulous/src/Fabulous.Core/Xamarin.Forms.Core.fs:11927
07-12 16:56:22.843 I/mono-stdout(31427): at Fabulous.Core.ProgramRunner2[model,msg].updateView (model updatedModel) [0x00067] in /Git/Github/Fabulous/src/Fabulous.Core/ElmishProgram.fs:92 07-12 16:56:22.843 I/mono-stdout(31427): at Fabulous.Core.ProgramRunner2[model,msg].processMsg (msg msg) [0x0002e] in /Git/Github/Fabulous/src/Fabulous.Core/ElmishProgram.fs:68

Stack trace for Repro 2

android.runtime.JavaProxyThrowable: System.NullReferenceException: Object reference not set to an instance of an object
  at Xamarin.Forms.Platform.Android.PageRenderer.Xamarin.Forms.Platform.Android.IOrderedTraversalController.UpdateTraversalOrder () [0x000ea] in <d498db4cf6c940a09b62e9279681494b>:0 
  at Xamarin.Forms.Platform.Android.PageRenderer.OnLayout (System.Boolean changed, System.Int32 l, System.Int32 t, System.Int32 r, System.Int32 b) [0x00013] in <d498db4cf6c940a09b62e9279681494b>:0 
  at Xamarin.Forms.Platform.Android.FormsViewGroup.n_OnLayout_ZIIII (System.IntPtr jnienv, System.IntPtr native__this, System.Boolean p0, System.Int32 p1, System.Int32 p2, System.Int32 p3, System.Int32 p4) [0x00008] in <662026c9033c41d3890f3b3e3eae3fde>:0 
  at (wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.34(intptr,intptr,bool,int,int,int,int)
--- End of stack trace from previous location where exception was thrown ---

  at Java.Interop.JniEnvironment+InstanceMethods.CallNonvirtualVoidMethod (Java.Interop.JniObjectReference instance, Java.Interop.JniObjectReference type, Java.Interop.JniMethodInfo method, Java.Interop.JniArgumentValue* args) [0x00089] in <3beddfcb1eb547cd8ce47c3097f6eaeb>:0 
  at Java.Interop.JniPeerMembers+JniInstanceMethods.InvokeVirtualVoidMethod (System.String encodedMember, Java.Interop.IJavaPeerable self, Java.Interop.JniArgumentValue* parameters) [0x0005d] in <3beddfcb1eb547cd8ce47c3097f6eaeb>:0 
  at Xamarin.Forms.Platform.Android.FormsViewGroup.MeasureAndLayout (System.Int32 p0, System.Int32 p1, System.Int32 p2, System.Int32 p3, System.Int32 p4, System.Int32 p5) [0x00090] in <662026c9033c41d3890f3b3e3eae3fde>:0 
  at Xamarin.Forms.Platform.Android.VisualElementTracker.UpdateLayout () [0x00163] in <d498db4cf6c940a09b62e9279681494b>:0 
  at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].UpdateLayout () [0x0001c] in <d498db4cf6c940a09b62e9279681494b>:0 
  at Xamarin.Forms.Platform.Android.AppCompat.Platform.Xamarin.Forms.Platform.Android.IPlatformLayout.OnLayout (System.Boolean changed, System.Int32 l, System.Int32 t, System.Int32 r, System.Int32 b) [0x0002b] in <d498db4cf6c940a09b62e9279681494b>:0 
  at Xamarin.Forms.Platform.Android.PlatformRenderer.OnLayout (System.Boolean changed, System.Int32 l, System.Int32 t, System.Int32 r, System.Int32 b) [0x00025] in <d498db4cf6c940a09b62e9279681494b>:0 
  at Android.Views.ViewGroup.n_OnLayout_ZIIII (System.IntPtr jnienv, System.IntPtr native__this, System.Boolean changed, System.Int32 l, System.Int32 t, System.Int32 r, System.Int32 b) [0x00009] in <ff9f3f3d4e134974a889db1b532c9b6e>:0 
  at (wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.29(intptr,intptr,bool,int,int,int,int)
	at md51558244f76c53b6aeda52c8a337f2c37.PlatformRenderer.n_onLayout(Native Method)
	at md51558244f76c53b6aeda52c8a337f2c37.PlatformRenderer.onLayout(PlatformRenderer.java:63)
	at android.view.View.layout(View.java:19828)
	at android.view.ViewGroup.layout(ViewGroup.java:6154)
	at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1083)
	at android.view.View.layout(View.java:19828)
	at android.view.ViewGroup.layout(ViewGroup.java:6154)
	at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
	at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
	at android.view.View.layout(View.java:19828)
	at android.view.ViewGroup.layout(ViewGroup.java:6154)
	at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
	at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
	at android.view.View.layout(View.java:19828)
	at android.view.ViewGroup.layout(ViewGroup.java:6154)
	at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
	at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
	at android.view.View.layout(View.java:19828)
	at android.view.ViewGroup.layout(ViewGroup.java:6154)
	at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1791)
	at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1635)
	at android.widget.LinearLayout.onLayout(LinearLayout.java:1544)
	at android.view.View.layout(View.java:19828)
	at android.view.ViewGroup.layout(ViewGroup.java:6154)
	at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
	at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
	at com.android.internal.policy.DecorView.onLayout(DecorView.java:765)
	at android.view.View.layout(View.java:19828)
	at android.view.ViewGroup.layout(ViewGroup.java:6154)
	at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2641)
	at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2346)
	at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1482)
	at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:7122)
	at android.view.Choreographer$CallbackRecord.run(Choreographer.java:983)
	at android.view.Choreographer.doCallbacks(Choreographer.java:795)
	at android.view.Choreographer.doFrame(Choreographer.java:723)
	at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:969)
	at android.os.Handler.handleCallback(Handler.java:794)
	at android.os.Handler.dispatchMessage(Handler.java:99)
	at android.os.Looper.loop(Looper.java:176)
	at android.app.ActivityThread.main(ActivityThread.java:6656)
	at java.lang.reflect.Method.invoke(Native Method)
	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547)
	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:873)

Repro

Repro 1

namespace ReproApp

open System.Diagnostics
open Fabulous
open Fabulous.XamarinForms
open Xamarin.Forms

module App = 
    type Model = 
      { Flag:bool }

    type Msg =
        |Flag


    let initModel = {Flag=true }

    let init () = initModel, Cmd.none



    let update msg model =
        match msg with
        |Flag->{model with Flag=not model.Flag},Cmd.none

    let view (model: Model) dispatch =
        View.ContentPage(
           content=View.Grid(
               rowdefs=["auto";"*"],
               children =
                   [
                     yield View.Button (text="SetFlag", command= (fun ()->dispatch Flag))
                     if(model.Flag) then yield (View.Label(text="Flag set")).GridRow(1)
                     else yield View.ListView(items=([1..100]|>List.map (fun x->View.Label(text=string x)))).GridRow(1)
                     
                     
                   ]
                   )
           )

    // Note, this declaration is needed if you enable LiveUpdate
    let program = Program.mkProgram init update view

type App () as app = 
    inherit Application ()

    let runner = 
        App.program
#if DEBUG
        |> Program.withConsoleTrace
#endif
        |> XamarinFormsProgram.run app

Repro 2

namespace NRERepro
open Fabulous
open Fabulous.XamarinForms
open Xamarin.Forms

module App = 
    type Model = A | B
    type Msg = OpenB
    let init () = A, Cmd.ofMsg OpenB
    let update OpenB model = B, Cmd.none
    let view model dispatch =
        match model with A -> View.BoxView Color.Green | B -> View.Button "B"
        
        // Removing does not affect bug, purely for visibility
        |> layoutBounds (Rectangle(0., 0., 1., 1.))
        |> layoutFlags AbsoluteLayoutFlags.All

        |> List.singleton
        |> fun x -> View.AbsoluteLayout x
        |> fun x -> View.ContentPage x
    // Note, this declaration is needed if you enable LiveUpdate
    let program = Program.mkProgram init update view

type App () as app = 
    inherit Application ()
    
    let runner = App.program |> XamarinFormsProgram.run app