[Bug] [Android] ArgumentOutOfRangeException in CollectionView: Adapter miscalculates item position when using CV Header

[janschoelchAtOK]

Description

When using the CollectionView in Xamarin.Forms 4.2 and using the new CV Header feature, the SelectableItemsViewAdapter seems to miscalculate the item positions.
This leads to unwanted behaviour (wrong item selections) and also to exceptions.

The issue exists since CollectionView Headers were introduced (so much love for this! :-)) for Android (which is XF4.2-pre1 I think).

As things run fine on iOS, I could not reproduce the error there. This is Android only.

I faced and reproduced this issue on an Huawei P Smart+ (2018) running Android 8.1. But a quick test on several Emulators gave me the same exception - so this is neither device-specific nor dependent on the OS version.

Steps to Reproduce

1. Add a simple CollectionView to a XF Project running XF4.2
2. Make CollectionView Selectable (SelectionMode="Single")
3. Add a Header to the CollectionView
4. Run your app and select any item --> The selected item is not correct.

OR (easier)

1. Start the attached Solution
2. Select any item

Expected Behavior (in attached repo)

• The dialog that appears should show the correct selection

Actual Behavior (in attached repo)

• The dialog shows the [SelectedItem + 1]
• When selecting the last item in the CollectionView ("I am teal"), the application crashes with an IndexOutOfRangeException as there is no [SelectedItem + 1].

StackTrace:

08-22 12:34:27.914 I/MonoDroid( 8272): UNHANDLED EXCEPTION: 08-22 12:34:27.973 I/MonoDroid( 8272): System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection. 08-22 12:34:27.973 I/MonoDroid( 8272): Parameter name: index 08-22 12:34:27.973 I/MonoDroid( 8272): at System.Collections.Generic.List'1[T].get_Item (System.Int32 index) [0x00009] in <d4a23bbd2f544c30a48c44dd622ce09f>:0 08-22 12:34:27.973 I/MonoDroid( 8272): at Xamarin.Forms.Platform.Android.SelectableItemsViewAdapter.UpdateFormsSelection (System.Int32 adapterPosition) [0x00020] in D:\a\1\s\Xamarin.Forms.Platform.Android\CollectionView\SelectableItemsViewAdapter.cs:138 08-22 12:34:27.973 I/MonoDroid( 8272): at Xamarin.Forms.Platform.Android.SelectableItemsViewAdapter.SelectableClicked (System.Object sender, System.Int32 adapterPosition) [0x00000] in D:\a\1\s\Xamarin.Forms.Platform.Android\CollectionView\SelectableItemsViewAdapter.cs:125 08-22 12:34:27.973 I/MonoDroid( 8272): at Xamarin.Forms.Platform.Android.SelectableViewHolder.OnViewHolderClicked (System.Int32 adapterPosition) [0x00000] in D:\a\1\s\Xamarin.Forms.Platform.Android\CollectionView\SelectableViewHolder.cs:51 08-22 12:34:27.973 I/MonoDroid( 8272): at Xamarin.Forms.Platform.Android.SelectableViewHolder.OnClick (Android.Views.View view) [0x00000] in D:\a\1\s\Xamarin.Forms.Platform.Android\CollectionView\SelectableViewHolder.cs:40 08-22 12:34:27.973 I/MonoDroid( 8272): at Android.Views.View+IOnClickListenerInvoker.n_OnClick_Landroid_view_View_ (System.IntPtr jnienv, System.IntPtr native__this, System.IntPtr native_v) [0x00011] in <b781ed64f1d743e7881ac038e0fbdf85>:0 08-22 12:34:27.973 I/MonoDroid( 8272): at (wrapper dynamic-method) System.Object.43(intptr,intptr,intptr)

Basic Information

• Version with issue: Xamarin.Forms 4.2
• Last known good version: None, as the issue exists since the first Version where CV headers were availabe for Android
• IDE: Visual Studio Professional 2017
• Platform Target Frameworks:
  • iOS: 12.1 (runs without Errors)
  • Android: 8.1
  • UWP: not tested
• Android Support Library Version: 28.0.01
• Nuget Packages: Xamarin.Forms 4.2-RC1 (4.2.0.709249)
• Affected Devices: Tablets and Phones

Screenshots

No visual error detected

Reproduction Link

CVHeaderDemo.zip

[janschoelchAtOK]

I just saw the changes that @hartez did in #7199, especially in the most recent commit.
As this issue is propably connected to #7121 and #7102, there is a chance that this may already be fixed by @hartez' PR

[hartez]

I just saw the changes that @hartez did in #7199, especially in the most recent commit.
As this issue is propably connected to #7121 and #7102, there is a chance that this may already be fixed by @hartez' PR

Just confirmed this with a build from PR #7199 - that PR does fix this issue.

[Toomas75]

It's back MAUI 8.0.6 , Android 8.1
crash log:
System.ArgumentOutOfRangeException
System.ArgumentOutOfRangeException: ArgumentOutOfRange_IndexMustBeLess Arg_ParamName_Name, index

System.Collections.Generic.List1[[System.Object, System.Private.CoreLib, Version=8.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].get_Item(Int32 ) System.Collections.Generic.List1[[System.Object, System.Private.CoreLib, Version=8.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].System.Collections.IList.get_Item(Int32 )
Microsoft.Maui.Controls.Handlers.Items.ObservableItemsSource.ElementAt(Int32 )
Microsoft.Maui.Controls.Handlers.Items.ObservableItemsSource.GetItem(Int32 )
Microsoft.Maui.Controls.Handlers.Items.UngroupedItemsSource.GetItem(Int32 )
Microsoft.Maui.Controls.Handlers.Items.SelectableItemsViewAdapter2[[Microsoft.Maui.Controls.ReorderableItemsView, Microsoft.Maui.Controls, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[Microsoft.Maui.Controls.Handlers.Items.IGroupableItemsViewSource, Microsoft.Maui.Controls, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].UpdateMauiSelection(Int32 ) Microsoft.Maui.Controls.Handlers.Items.SelectableItemsViewAdapter2[[Microsoft.Maui.Controls.ReorderableItemsView, Microsoft.Maui.Controls, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[Microsoft.Maui.Controls.Handlers.Items.IGroupableItemsViewSource, Microsoft.Maui.Controls, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].SelectableClicked(Object sender, Int32 adapterPosition)
Microsoft.Maui.Controls.Handlers.Items.SelectableViewHolder.OnViewHolderClicked(Int32 )
Microsoft.Maui.Controls.Handlers.Items.SelectableViewHolder.OnClick(View )
Android.Views.View.IOnClickListenerInvoker.n_OnClick_Landroid_view_View_(IntPtr jnienv, IntPtr native__this, IntPtr native_v)
Android.Runtime.JNINativeWrapper.Wrap_JniMarshal_PPL_V(_JniMarshal_PPL_V callback, IntPtr jnienv, IntPtr klazz, IntPtr p0)

[alexsmi-noveo]

Confirm, the same for me: MAUI 8.0.20:

System.Collections.Generic.List1[[Pootsy.Mobile.Models.Bookings.BookingListItem, Pootsy.Mobile, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].get_Item(Int32 ) System.Collections.Generic.List1[[Pootsy.Mobile.Models.Bookings.BookingListItem, Pootsy.Mobile, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].System.Collections.IList.get_Item(Int32 )
Microsoft.Maui.Controls.Handlers.Items.ListSource.GetItem(Int32 position)
AndroidX.RecyclerView.Widget.RecyclerView.Adapter.n_OnBindViewHolder_Landroidx_recyclerview_widget_RecyclerView_ViewHolder_I(IntPtr jnienv, IntPtr native__this, IntPtr native_holder, Int32 position)
Android.Runtime.JNINativeWrapper.Wrap_JniMarshal_PPLI_V(_JniMarshal_PPLI_V callback, IntPtr jnienv, IntPtr klazz, IntPtr p0, Int32 p1)