[Android] CollectionView: VirtualView cannot be null here, when clearing and adding items on second navigation #12219
Description
Description
An Exception occurs when adding item to ObservableCollection with an EmptyView after having navigated to the same page for a second time.
System.InvalidOperationException: 'VirtualView cannot be null here'
The exception occurs:
- Only on Android (works fine on Windows)
- Only when navigating to the page a second (or third...) time
- I tried using VS 17.4.3, as well as 17.5.0 Preview 2.0, both latest as of today
maui-android 7.0.52/7.0.100 VS 17.4.33205.214, VS 17.5.33209.295 - Using both
CollectionView EmptyView="something"as well as using separate<CollectionView.EmptyView><ContentView>...
Steps to Reproduce
- Create a File > New .NET MAUI App
- Add a second ContentPage to the project, named "Page2"
- In AppShell.xaml.cs add:
Routing.RegisterRoute("Page2", typeof(Page2)); - In MauiProgram.cs add:
builder.Services.AddScoped<Page2>(); - In Page2.xaml remove the
Labeland replace with:
<CollectionView ItemsSource="{Binding Values}">
<CollectionView.EmptyView>
<ContentView>
<Label Text="No items"
FontAttributes="Bold" />
</ContentView>
</CollectionView.EmptyView>
<CollectionView.ItemTemplate>
<DataTemplate x:DataType="x:String">
<Label Text="{Binding .}" />
</DataTemplate>
</CollectionView.ItemTemplate>
</CollectionView>
<Button
Text="Load items"
Pressed="Button_Pressed" />- In Page2.xaml.cs replace the class with:
public partial class Page2 : ContentPage
{
public ObservableCollection<string> Values { get; set; } = new();
public Page2()
{
InitializeComponent();
this.BindingContext = this;
}
private async void Button_Pressed(object sender, EventArgs e)
{
Values.Clear();
await Task.Delay(1000);
for (int i = 1; i <= 5; i++)
Values.Add($"Item #{i}");
}
}- In MainPage.xaml.cs modify
OnCounterClickedas follows:
private async void OnCounterClicked(object sender, EventArgs e)
{
count++;
if (count == 1)
CounterBtn.Text = $"Clicked {count} time";
else
CounterBtn.Text = $"Clicked {count} times";
SemanticScreenReader.Announce(CounterBtn.Text);
await Shell.Current.GoToAsync("/Page2");
}- Run the app on Android
- Click the button on MainPage
- Click the button on Page2 two or more times --> works fine
- Go back to MainPage
- Click the button on MainPage again
- Click the button on Page2 --> Exception occurrs:
System.InvalidOperationException: VirtualView cannot be null here at Microsoft.Maui.Handlers.ViewHandler`2[[Microsoft.Maui.Controls.ReorderableItemsView, Microsoft.Maui.Controls, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[AndroidX.RecyclerView.Widget.RecyclerView, Xamarin.AndroidX.RecyclerView, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].get_VirtualView() in D:\a\_work\1\s\src\Core\src\Handlers\View\ViewHandlerOfT.cs:line 42 at Microsoft.Maui.Controls.Handlers.Items.StructuredItemsViewHandler`1[[Microsoft.Maui.Controls.ReorderableItemsView, Microsoft.Maui.Controls, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].GetItemsLayout() in D:\a\_work\1\s\src\Controls\src\Core\Handlers\Items\StructuredItemsViewHandler.Android.cs:line 10 at Microsoft.Maui.Controls.Handlers.Items.MauiRecyclerView`3[[Microsoft.Maui.Controls.ReorderableItemsView, Microsoft.Maui.Controls, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[Microsoft.Maui.Controls.Handlers.Items.GroupableItemsViewAdapter`2[[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]], 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]].UpdateLayoutManager() in D:\a\_work\1\s\src\Controls\src\Core\Handlers\Items\Android\MauiRecyclerView.cs:line 288 at Microsoft.Maui.Controls.Handlers.Items.MauiRecyclerView`3[[Microsoft.Maui.Controls.ReorderableItemsView, Microsoft.Maui.Controls, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[Microsoft.Maui.Controls.Handlers.Items.GroupableItemsViewAdapter`2[[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]], 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]].UpdateEmptyViewVisibility() in D:\a\_work\1\s\src\Controls\src\Core\Handlers\Items\Android\MauiRecyclerView.cs:line 552 at Microsoft.Maui.Controls.Handlers.Items.DataChangeObserver.OnItemRangeInserted(Int32 positionStart, Int32 itemCount) in D:\a\_work\1\s\src\Controls\src\Core\Handlers\Items\Android\DataChangeObserver.cs:line 53 at AndroidX.RecyclerView.Widget.RecyclerView.AdapterDataObserver.n_OnItemRangeInserted_II(IntPtr jnienv, IntPtr native__this, Int32 positionStart, Int32 itemCount) in C:\a\_work\3\s\generated\androidx.recyclerview.recyclerview\obj\Release\net6.0-android\generated\src\AndroidX.RecyclerView.Widget.RecyclerView.cs:line 1124 at Android.Runtime.JNINativeWrapper.Wrap_JniMarshal_PPII_V(_JniMarshal_PPII_V callback, IntPtr jnienv, IntPtr klazz, Int32 p0, Int32 p1) in /Users/runner/work/1/s/xamarin-android/src/Mono.Android/Android.Runtime/JNINativeWrapper.g.cs:line 154
Link to public reproduction project repository
https://github.com/jaldinger/MauiAppRepro1.App
Version with bug
7.0
Last version that worked well
Unknown/Other
Affected platforms
Android
Affected platform versions
Android (tested 8.1)
Did you find any workaround?
Removing the EmptyView from the CollectionView avoids the exception (but removes the EmtpyView).
Relevant log output
No response