Maui Android Crash CarouselView IndicatorView on navigating second time

[lucianparvu]

Description

Maui Android Crash when there is CarouselView with IndicatorView and navigating second time to the page .

`

        <CarouselView.ItemTemplate>
            <DataTemplate x:DataType="model:ProductFileV2">                    
                <StackLayout>
                    <Frame HasShadow="True"
                   BorderColor="DarkGray"
                   CornerRadius="5"
                   Margin="20"
                   HeightRequest="300"
                   HorizontalOptions="Center"
                   VerticalOptions="CenterAndExpand">
                        <StackLayout>
                            <local:PinchToZoomContainer>
                                <Image Source="{Binding ThumbnailHostPathPublic}"
                               Aspect="AspectFill"
                               HeightRequest="150"
                               WidthRequest="150"
                               HorizontalOptions="Center" />
                            </local:PinchToZoomContainer>
                        </StackLayout>
                    </Frame>
                </StackLayout>                   
                </DataTemplate>
        </CarouselView.ItemTemplate>
    </CarouselView>
    <IndicatorView x:Name="myIndicator"
               IndicatorColor="LightGray"
               SelectedIndicatorColor="DarkGray"
               HorizontalOptions="Center" />

public ObservableCollection ProductFileList { get; set; } = new ObservableCollection();
void LoadProductFiles()
{
if (IsBusyProductFiles) { return; }
IsBusyProductFiles = true;

        Task.Run(async () =>
        {                
            var items = await _ProductService.GetProductFiles(SearchModel);
            Application.Current.Dispatcher.Dispatch(() =>
            {                   
                ProductFileList.Clear();                   
                items?.Where(p => p.ProductFileType?.ProductFileTypeAction == ProductFileTypeAction.IsGallery)?
                                    .OrderBy(p => p.Importance)?
                                    .ToList()?.ForEach(p => ProductFileList.Add(p));

                IsBusyProductFiles = false;
            });
        });
    }

Steps to Reproduce

Link to public reproduction project repository

dont have

Version with bug

7.0 (current)

Last version that worked well

Unknown/Other

Affected platforms

Android

Affected platform versions

Android

Did you find any workaround?

No

Relevant log output

Time	Device Name	Type	PID	Tag	Message
11-12 16:40:11.425	pixel_5_-_api_33	Error	1788	AndroidRuntime	android.runtime.JavaProxyThrowable: System.InvalidOperationException: PlatformView cannot be null here
   at Microsoft.Maui.Handlers.ViewHandler`2[[Microsoft.Maui.IIndicatorView, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[Microsoft.Maui.Platform.MauiPageControl, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].get_PlatformView()
   at Microsoft.Maui.Handlers.IndicatorViewHandler.OnDisconnectHandler(View platformView)
   at Microsoft.Maui.Handlers.ViewHandler.OnDisconnectHandler(Object platformView)
   at Microsoft.Maui.Handlers.ElementHandler.DisconnectHandler(Object platformView)
   at Microsoft.Maui.Handlers.ElementHandler.Microsoft.Maui.IElementHandler.DisconnectHandler()
   at Microsoft.Maui.Controls.Element.SetHandler(IElementHandler newHandler)
   at Microsoft.Maui.Controls.Element.set_Handler(IElementHandler value)
   at Microsoft.Maui.Controls.VisualElement.Microsoft.Maui.IElement.set_Handler(IElementHandler value)
   at Microsoft.Maui.Platform.ElementExtensions.ToHandler(IElement view, IMauiContext context)
   at Microsoft.Maui.Platform.ElementExtensions.ToPlatform(IElement view, IMauiContext context)
   at Microsoft.Maui.Handlers.LayoutHandler.SetVirtualView(IView view)
   at Microsoft.Maui.Handlers.ViewHandler`2[[Microsoft.Maui.ILayout, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[Microsoft.Maui.Platform.LayoutViewGroup, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].SetVirtualView(IElement view)
   at Microsoft.Maui.Controls.Element.SetHandler(IElementHandler newHandler)
   at Microsoft.Maui.Controls.Element.set_Handler(IElementHandler value)
   at Microsoft.Maui.Controls.VisualElement.Microsoft.Maui.IElement.set_Handler(IElementHandler value)
   at Microsoft.Maui.Platform.ElementExtensions.ToHandler(IElement view, IMauiContext context)
   at Microsoft.Maui.Platform.ElementExtensions.ToPlatform(IElement view, IMauiContext context)
   at Microsoft.Maui.Handlers.ContentViewHandler.UpdateContent(IContentViewHandler handler)
   at Microsoft.Maui.Handlers.ContentViewHandler.MapContent(IContentViewHandler handler, IContentView page)
   at Microsoft.Maui.PropertyMapper`2.<>c__DisplayClass5_0[[Microsoft.Maui.IContentView, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[Microsoft.Maui.Handlers.IContentViewHandler, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].<Add>b__0(IElementHandler h, IElement v)
   at Microsoft.Maui.PropertyMapper.UpdatePropertyCore(String key, IElementHandler viewHandler, IElement virtualView)
   at Microsoft.Maui.PropertyMapper.UpdateProperties(IElementHandler viewHandler, IElement virtualView)
   at Microsoft.Maui.Handlers.ElementHandler.SetVirtualView(IElement view)
   at Microsoft.Maui.Handlers.ViewHandler.SetVirtualView(IElement element)
   at Microsoft.Maui.Handlers.ViewHandler`2[[Microsoft.Maui.IContentView, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[Microsoft.Maui.Platform.ContentViewGroup, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].SetVirtualView(IView view)
   at Microsoft.Maui.Handlers.ContentViewHandler.SetVirtualView(IView view)
   at Microsoft.Maui.Handlers.ViewHandler`2[[Microsoft.Maui.IContentView, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[Microsoft.Maui.Platform.ContentViewGroup, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].SetVirtualView(IElement view)
   at Microsoft.Maui.Controls.Element.SetHandler(IElementHandler newHandler)
   at Microsoft.Maui.Controls.Element.set_Handler(IElementHandler value)
   at Microsoft.Maui.Controls.VisualElement.Microsoft.Maui.IElement.set_Handler(IElementHandler value)
   at Microsoft.Maui.Platform.ElementExtensions.ToHandler(IElement view, IMauiContext context)
   at Microsoft.Maui.Platform.ViewExtensions.ToHandler(IView view, IMauiContext context)
   at Microsoft.Maui.Controls.Platform.Compatibility.ShellContentFragment.OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
   at AndroidX.Fragment.App.Fragment.n_OnCreateView_Landroid_view_LayoutInflater_Landroid_view_ViewGroup_Landroid_os_Bundle_(IntPtr jnienv, IntPtr native__this, IntPtr native_inflater, IntPtr native_container, IntPtr native_savedInstanceState)
   at Android.Runtime.JNINativeWrapper.Wrap_JniMarshal_PPLLL_L(_JniMarshal_PPLLL_L callback, IntPtr jnienv, IntPtr klazz, IntPtr p0, IntPtr p1, IntPtr p2)
	at crc640ec207abc449b2ca.ShellContentFragment.n_onCreateView(Native Method)
	at crc640ec207abc449b2ca.ShellContentFragment.onCreateView(ShellContentFragment.java:62)
	at androidx.fragment.app.Fragment.performCreateView(Fragment.java:3104)
	at androidx.fragment.app.FragmentStateManager.createView(FragmentStateManager.java:524)
	at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:261)
	at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:1890)
	at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1808)
	at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:1751)
	at androidx.fragment.app.FragmentManager$5.run(FragmentManager.java:538)
	at android.os.Handler.handleCallback(Handler.java:942)
	at android.os.Handler.dispatchMessage(Handler.java:99)
	at android.os.Looper.loopOnce(Looper.java:201)
	at android.os.Looper.loop(Looper.java:288)
	at android.app.ActivityThread.main(ActivityThread.java:7892)
	at java.lang.reflect.Method.invoke(Native Method)
	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548)
	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:936)

[ghost]

We've moved this issue to the Backlog milestone. This means that it is not going to be worked on for the coming release. We will reassess the backlog following the current release and consider this item at that time. To learn more about our issue management process and to have better expectation regarding different types of issues you can read our Triage Process.

[jaldinger]

I am getting a "VirtualView cannot be null here" exception when navigating a second time to a page and then clearing and re-adding elements to an ObservableCollection bound to a CollectionView. Only happens on Android and only in the exact moment the first new element is added to the ObservableCollection. Is my issue likely to be related to and/or fixed by this issue?

[Fric-88]

I am seeing the same issue as @jaldinger "VirtualView cannot be null here" when adding first item to ObservableCollection. Im not 100% sure, but i think this started happening to me after switching to .NET 7

[jaldinger]

I am seeing the same issue as @jaldinger "VirtualView cannot be null here" when adding first item to ObservableCollection. Im not 100% sure, but i think this started happening to me after switching to .NET 7

Does this happen to you already on the first navigation, or only on the second, like to me?

[Fric-88]

I am seeing the same issue as @jaldinger "VirtualView cannot be null here" when adding first item to ObservableCollection. Im not 100% sure, but i think this started happening to me after switching to .NET 7

Does this happen to you already on the first navigation, or only on the second, like to me?

It does not happen to me when navigating, but when Invoking an Add in my ViewModel after recieving a PubSub message. This only Happens if the Collection is empty and only on the first element being added.

    [ObservableProperty]
    public ObservableCollection <Template> templates;

    public TemplatesViewModel(TemplatesManager manager)
    {
        Title = "Templates";
        templatesManager = manager;

        //Initial Template listing -> On Page Load
        Task.Run(RefreshTeplatesAsync);

        //Subscibe to Messages
        WeakReferenceMessenger.Default.Register<TemplateSavedMessage>(this, (r, m) =>
        {
            MainThread.BeginInvokeOnMainThread(() =>
            {
                Templates.Add(m.Value); //Exception happens here
            });
        });

        WeakReferenceMessenger.Default.Register<TemplateDeletedMessage>(this, (r, m) =>
        {
            MainThread.BeginInvokeOnMainThread(() =>
            {
                Templates.Remove(m.Value);
            });
        });
    }

[espenrl]

This fixes it for me until it is patched. Based on #12141

           .ConfigureMauiHandlers(handlers =>
            {
#if ANDROID
                handlers.AddHandler(typeof(IndicatorView), typeof(FixCrashIndicatorViewHandler));
#endif
            })

/// <summary>
/// https://github.com/dotnet/maui/pull/12141
/// </summary>
public sealed class FixCrashIndicatorViewHandler : ViewHandler<IIndicatorView, MauiPageControl>, IIndicatorViewHandler
{
    public static readonly IPropertyMapper<IIndicatorView, IIndicatorViewHandler> Mapper = new PropertyMapper<IIndicatorView, IIndicatorViewHandler>(ViewMapper)
    {
        [nameof(IIndicatorView.Count)] = MapCount,
        [nameof(IIndicatorView.Position)] = MapPosition,
        [nameof(IIndicatorView.HideSingle)] = MapHideSingle,
        [nameof(IIndicatorView.MaximumVisible)] = MapMaximumVisible,
        [nameof(IIndicatorView.IndicatorSize)] = MapIndicatorSize,
        [nameof(IIndicatorView.IndicatorColor)] = MapIndicatorColor,
        [nameof(IIndicatorView.SelectedIndicatorColor)] = MapSelectedIndicatorColor,
        [nameof(IIndicatorView.IndicatorsShape)] = MapIndicatorShape
    };

    public static readonly CommandMapper<IIndicatorView, IIndicatorViewHandler> CommandMapper = new(ViewCommandMapper)
    {
    };

    public FixCrashIndicatorViewHandler() : base(Mapper)
    {
    }

    public FixCrashIndicatorViewHandler(IPropertyMapper? mapper)
        : base(mapper ?? Mapper, CommandMapper)
    {
    }

    public FixCrashIndicatorViewHandler(IPropertyMapper? mapper, CommandMapper? commandMapper)
        : base(mapper ?? Mapper, commandMapper ?? CommandMapper)
    {
    }

    IIndicatorView IIndicatorViewHandler.VirtualView => VirtualView;

    MauiPageControl IIndicatorViewHandler.PlatformView => PlatformView;

    protected override MauiPageControl CreatePlatformView()
    {
        return new MauiPageControl(Context);
    }

    protected override void ConnectHandler(MauiPageControl platformView)
    {
        base.ConnectHandler(platformView);

        if (platformView is MauiPageControl pageControl)
            pageControl.SetIndicatorView(VirtualView);
    }

    protected override void DisconnectHandler(MauiPageControl platformView)
    {
        base.DisconnectHandler(platformView);

        if (platformView is MauiPageControl pageControl)
            pageControl.SetIndicatorView(null);
    }

    public static void MapCount(IIndicatorViewHandler handler, IIndicatorView indicator)
    {
        handler.PlatformView.UpdateIndicatorCount();
    }

    public static void MapPosition(IIndicatorViewHandler handler, IIndicatorView indicator)
    {
        handler.PlatformView.UpdatePosition();
    }

    public static void MapHideSingle(IIndicatorViewHandler handler, IIndicatorView indicator)
    {
        handler.PlatformView.UpdateIndicatorCount();
    }

    public static void MapMaximumVisible(IIndicatorViewHandler handler, IIndicatorView indicator)
    {
        handler.PlatformView.UpdateIndicatorCount();
    }

    public static void MapIndicatorSize(IIndicatorViewHandler handler, IIndicatorView indicator)
    {
        handler.PlatformView.ResetIndicators();
    }

    public static void MapIndicatorColor(IIndicatorViewHandler handler, IIndicatorView indicator)
    {
        handler.PlatformView.ResetIndicators();
    }

    public static void MapSelectedIndicatorColor(IIndicatorViewHandler handler, IIndicatorView indicator)
    {
        handler.PlatformView.ResetIndicators();
    }

    public static void MapIndicatorShape(IIndicatorViewHandler handler, IIndicatorView indicator)
    {
        handler.PlatformView.ResetIndicators();
    }
}

[Kremed]

This fixes it for me until it is patched. Based on #12141

           .ConfigureMauiHandlers(handlers =>
            {
#if ANDROID
                handlers.AddHandler(typeof(IndicatorView), typeof(FixCrashIndicatorViewHandler));
#endif
            }) ```

Works Great For Me