We are unable to reproduce this crash, but our App.Center Analytics is reporting this error from some, but not all, of our customers

Version 2019.2.708

Crash::

System.NullReferenceException: Object reference not set to an instance of an object

IOrderedTraversalController.UpdateTraversalOrder ()
VisualElementRenderer`1[TElement].UpdateParentPageTraversalOrder ()
VisualElementRenderer`1[TElement].OnElementPropertyChanged (System.Object sender, System.ComponentModel.PropertyChangedEventArgs e)
(wrapper delegate-invoke) <Module>.invoke_void_object_PropertyChangedEventArgs(object,System.ComponentModel.PropertyChangedEventArgs)
BindableObject.OnPropertyChanged (System.String propertyName)
Element.OnPropertyChanged (System.String propertyName)
Element.set_Parent (Xamarin.Forms.Element value)
RadViewContainer.DetachInnerView ()
RadViewContainer.set_View (Xamarin.Forms.View value)
SideDrawerRenderer.RetireViewContainer (Telerik.XamarinForms.Common.Android.RadViewContainer viewContainer)
SideDrawerRenderer.RetireMainContent ()
SideDrawerRenderer.RetireViewContainers ()
SideDrawerRenderer.OnElementDetached (Telerik.XamarinForms.Primitives.RadSideDrawer oldElement)
AndroidRendererBase`2[S,T].Dispose (System.Boolean disposing)
Object.Dispose ()
VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing)
Platform+DefaultRenderer.Dispose (System.Boolean disposing)
Object.Dispose ()
VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing)
Platform+DefaultRenderer.Dispose (System.Boolean disposing)
Object.Dispose ()
VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing)
Platform+DefaultRenderer.Dispose (System.Boolean disposing)
Object.Dispose ()
VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing)
Platform+DefaultRenderer.Dispose (System.Boolean disposing)
Object.Dispose ()
VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing)
Platform+DefaultRenderer.Dispose (System.Boolean disposing)
Object.Dispose ()
VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing)
Platform+DefaultRenderer.Dispose (System.Boolean disposing)
Object.Dispose ()
VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing)
Platform+DefaultRenderer.Dispose (System.Boolean disposing)
Object.Dispose ()
VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing)
PageRenderer.Dispose (System.Boolean disposing)
Object.Dispose ()
FragmentContainer.OnDestroyView ()
Fragment.n_OnDestroyView (System.IntPtr jnienv, System.IntPtr native__this)
(wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.74(intptr,intptr)

Hi Didi & IanV

We're also getting this crash report from App Center (only in Android happend in the last 7 days to 15 different users out of ~200 active users on 15 distinct devices)

We are not using SideDrawer

Telerik version: v2019.3.1004

Xamarin.Forms 4.2.0

CellContainerBase.Dispose (System.Boolean disposing)
System.NullReferenceException: Object reference not set to an instance of an object

Stack traces
IOrderedTraversalController.UpdateTraversalOrder ()
VisualElementRenderer`1[TElement].UpdateParentPageTraversalOrder ()
VisualElementRenderer`1[TElement].OnElementPropertyChanged (System.Object sender, System.ComponentModel.PropertyChangedEventArgs e)
(wrapper delegate-invoke) <Module>.invoke_void_object_PropertyChangedEventArgs(object,System.ComponentModel.PropertyChangedEventArgs)
BindableObject.OnPropertyChanged (System.String propertyName)
Element.OnPropertyChanged (System.String propertyName)
Element.set_Parent (Xamarin.Forms.Element value)
Element.OnChildRemoved (Xamarin.Forms.Element child)
ViewCell.set_View (Xamarin.Forms.View value)
CellContainerBase.Dispose (System.Boolean disposing)
Object.Dispose ()
FormsListViewDataSourceAdapterBase.ClearCachedViews ()
RadListViewDataSourceAdapter.ClearCachedViews ()
RadListViewDataSourceAdapter.Dispose (System.Boolean disposing)
Object.Dispose ()
ListViewRenderer.OnElementDetached (Telerik.XamarinForms.DataControls.RadListView oldElement)
AndroidRendererBase`2[S,T].Dispose (System.Boolean disposing)
Object.Dispose ()
VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing)
Platform+DefaultRenderer.Dispose (System.Boolean disposing)
Object.Dispose ()
VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing)
Platform+DefaultRenderer.Dispose (System.Boolean disposing)
Object.Dispose ()
VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing)
Platform+DefaultRenderer.Dispose (System.Boolean disposing)
Object.Dispose ()
VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing)
PageRenderer.Dispose (System.Boolean disposing)
Object.Dispose ()
FragmentContainer.OnDestroyView ()
Fragment.n_OnDestroyView (System.IntPtr jnienv, System.IntPtr native__this)
(wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.41(intptr,intptr)

Thanks in advance

Roei

Hi Afi,

Thank you for the provided details.

Regarding to the nullreference exception we have a bug report logged in our feedback portal: 

https://feedback.telerik.com/xamarin/1418464-android-nullreferenceexception-is-thrown-when-navigating-back-and-using-xamarin-forms-4-1

The issue was reproduced with ListView, SlideView, SideDrawer and DataGrid controls. I have noticed from the crash you have provided - the exception is for the listview control.

We have added an update in the feedback item regarding this crash. I have pasted the update info in this forum thread:

UPDATE:
The issue is confirmed to be in Xamarin.Forms framework. A fix is already provided. The Xamarin.Forms 4.3 version will contain the fix.

Could you please update the Xamarin.Forms version to 4.3 or higher and check whether this solves the issue.

Give the suggestion a try and let me know how it goes.

Regards,
Didi
Progress Telerik