NullReferenceException in CollectionView

Question

NullReferenceException in CollectionView

Closed this issue 2 years ago · 4 comments

Platform:

OS: Android
Device: Samsung S20 Ultra 5G
Sdk vervion: Android 12 (API 31)
Xamarin.Forms: [5.0.0.2337]
Sharpnado.CollectionView: 2.0.0
Sharpnado.Shadows: 1.2.0
Sharpnado.Tabs:2.2.0

Describe the bug
When i use the Horizontal List View with ObservableCollection, or List, as ItemSource the ListView return a NullReferenceException.
I already tried in various implementetion, with CollectionView(Sharpnado, not the standard), but in all implemention i have the same error.
If i remove the implementetion of HorizontalListView and insert a CollectionView (standard) the application continue correctly.

To Reproduce
Steps to reproduce the behavior:
ViewModel:

using Microsoft.Extensions.Logging;
using App.Infrastructure.ApiInterface;
using App.Models.Filters;
using App.Models.Ticket;
using Sharpnado.CollectionView.Paging;
using Sharpnado.CollectionView.Services;
using Sharpnado.CollectionView.ViewModels;
using Sharpnado.Presentation.Forms;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;
using Xamarin.CommunityToolkit.UI.Views;

namespace App.ViewModels
{
    public class DashboardViewModel : BaseViewModel
    {
        private readonly ILogger<DashboardViewModel> _logger;
        private readonly ITicketsApi _ticketsApi;
        private LayoutState groupState;

        public ObservableCollection<TicketTable> Tickets { get; set; }

        public LayoutState GroupState
        {
            get => groupState;
            set => SetProperty(ref groupState, value);
        }

        public DashboardViewModel(ILogger<DashboardViewModel> logger, ITicketsApi ticketsApi)
        {
            _logger = logger;
            _ticketsApi = ticketsApi;
            Title = "Dashboard";
            Tickets = new();
        }

        public async void InitViewModel()
        {
            try
            {
                GroupState = LayoutState.Loading;
                Tickets = new(await _ticketsApi.GetTicketsAsync());
                OnPropertyChanged(nameof(Tickets));
                GroupState = LayoutState.Success;
            }
            catch (Exception e)
            {
                _logger.LogError(e, MethodBase.GetCurrentMethod().Name);
            }
        }
    }
}

View:

<?xml version="1.0" encoding="UTF-8" ?>
<ContentView
    x:Class="App.Views.DashboardView"
    xmlns="http://xamarin.com/schemas/2014/forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    xmlns:loader="clr-namespace:Sharpnado.Presentation.Forms.CustomViews;assembly=Sharpnado.TaskLoaderView"
    xmlns:models="clr-namespace:App.Models"
    xmlns:shv="http://sharpnado.com"
    xmlns:viewmodels="clr-namespace:App.ViewModels"
    xmlns:xct="http://xamarin.com/schemas/2020/toolkit"
    x:DataType="viewmodels:DashboardViewModel"
    >
    <ContentView.Content>
        <StackLayout xct:StateLayout.CurrentState="{Binding GroupState}">
            <xct:StateLayout.StateViews>
                <xct:StateView StateKey="Success">
                    <StackLayout>
                        <Label Text="Dashboard" TextColor="Black" />
                        <shv:HorizontalListView
                            Grid.Row="3"
                            Margin="-16,8"
                            CollectionPadding="0,8"
                            ItemHeight="144"
                            ItemSpacing="8"
                            ItemWidth="144"
                            ItemsSource="{Binding Tickets}"
                            SnapStyle="Center"
                            >
                            <shv:HorizontalListView.ItemTemplate>
                                <DataTemplate x:DataType="models:TicketTable">
                                    <ViewCell>
                                        <Label Text="{Binding TicketName}" />
                                    </ViewCell>
                                </DataTemplate>
                            </shv:HorizontalListView.ItemTemplate>
                        </shv:HorizontalListView>
                    </StackLayout>
                </xct:StateView>
                <xct:StateView StateKey="Loading">
                    <StackLayout>
                        <ActivityIndicator
                            IsEnabled="True"
                            IsRunning="True"
                            Color="{DynamicResource Primary}"
                            />
                    </StackLayout>
                </xct:StateView>
            </xct:StateLayout.StateViews>
        </StackLayout>
    </ContentView.Content>
</ContentView>

View.cs:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using Xamarin.Forms;
using Xamarin.Forms.Xaml;

namespace App.Views
{
    [XamlCompilation(XamlCompilationOptions.Compile)]
    public partial class DashboardView : ContentView
    {
        private readonly DashboardViewModel ViewModel = Startup.ServiceProvider.GetService<DashboardViewModel>();
        public DashboardView()
        {
            InitializeComponent();
            BindingContext = ViewModel;
        }

        protected override void OnBindingContextChanged()
        {
            base.OnBindingContextChanged();
            ViewModel.InitViewModel();
        }
    }

Exceptions (if applicable)

Object reference not set to an instance of an object.
Sharpnado.CollectionView.Droid
at Sharpnado.CollectionView.Droid.Renderers.SpaceItemDecoration..ctor (System.Int32 spaceDp) [0x00006] in D:\Dev\Sharpnado\src\Sharpnado.HorizontalListView\Sharpnado.CollectionView.Droid\Renderers\ResponsiveGridLayoutManager.cs:31 
  at Sharpnado.CollectionView.Droid.Renderers.CollectionViewRenderer.SetListLayout (AndroidX.RecyclerView.Widget.RecyclerView recyclerView) [0x00099] in D:\Dev\Sharpnado\src\Sharpnado.HorizontalListView\Sharpnado.CollectionView.Droid\Renderers\CollectionViewRenderer.cs:251 
  at Sharpnado.CollectionView.Droid.Renderers.CollectionViewRenderer.CreateView (Sharpnado.CollectionView.RenderedViews.CollectionView collection) [0x00038] in D:\Dev\Sharpnado\src\Sharpnado.HorizontalListView\Sharpnado.CollectionView.Droid\Renderers\CollectionViewRenderer.cs:198 
  at Sharpnado.CollectionView.Droid.Renderers.CollectionViewRenderer.OnElementChanged (Xamarin.Forms.Platform.Android.ElementChangedEventArgs`1[TElement] e) [0x000bb] in D:\Dev\Sharpnado\src\Sharpnado.HorizontalListView\Sharpnado.CollectionView.Droid\Renderers\CollectionViewRenderer.cs:89 
  at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].SetElement (TElement element) [0x000cb] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:241 
  at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].Xamarin.Forms.Platform.Android.IVisualElementRenderer.SetElement (Xamarin.Forms.VisualElement element) [0x00033] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:131 
  at Xamarin.Forms.Platform.Android.Platform.CreateRenderer (Xamarin.Forms.VisualElement element, Android.Content.Context context) [0x0003e] in D:\a\1\s\Xamarin.Forms.Platform.Android\Platform.cs:358 
  at Xamarin.Forms.Platform.Android.VisualElementPackager.AddChild (Xamarin.Forms.VisualElement view, Xamarin.Forms.Platform.Android.IVisualElementRenderer oldRenderer, Xamarin.Forms.Platform.Android.RendererPool pool, System.Boolean sameChildren) [0x000b3] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementPackager.cs:140 
  at Xamarin.Forms.Platform.Android.VisualElementPackager.SetElement (Xamarin.Forms.VisualElement oldElement, Xamarin.Forms.VisualElement newElement) [0x00163] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementPackager.cs:351 
  at Xamarin.Forms.Platform.Android.VisualElementPackager.Load () [0x00000] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementPackager.cs:112 
  at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].SetPackager (Xamarin.Forms.Platform.Android.VisualElementPackager packager) [0x00007] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:481 
  at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].SetElement (TElement element) [0x000e8] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:244 
  at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].Xamarin.Forms.Platform.Android.IVisualElementRenderer.SetElement (Xamarin.Forms.VisualElement element) [0x00033] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:131 
  at Xamarin.Forms.Platform.Android.Platform.CreateRenderer (Xamarin.Forms.VisualElement element, Android.Content.Context context) [0x0003e] in D:\a\1\s\Xamarin.Forms.Platform.Android\Platform.cs:358 
  at Xamarin.Forms.Platform.Android.VisualElementPackager.AddChild (Xamarin.Forms.VisualElement view, Xamarin.Forms.Platform.Android.IVisualElementRenderer oldRenderer, Xamarin.Forms.Platform.Android.RendererPool pool, System.Boolean sameChildren) [0x000b3] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementPackager.cs:140 
  at Xamarin.Forms.Platform.Android.VisualElementPackager.SetElement (Xamarin.Forms.VisualElement oldElement, Xamarin.Forms.VisualElement newElement) [0x00163] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementPackager.cs:351 
  at Xamarin.Forms.Platform.Android.VisualElementPackager.Load () [0x00000] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementPackager.cs:112 
  at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].SetPackager (Xamarin.Forms.Platform.Android.VisualElementPackager packager) [0x00007] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:481 
  at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].SetElement (TElement element) [0x000e8] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:244 
  at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].Xamarin.Forms.Platform.Android.IVisualElementRenderer.SetElement (Xamarin.Forms.VisualElement element) [0x00033] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:131 
  at Xamarin.Forms.Platform.Android.Platform.CreateRenderer (Xamarin.Forms.VisualElement element, Android.Content.Context context) [0x0003e] in D:\a\1\s\Xamarin.Forms.Platform.Android\Platform.cs:358 
  at Xamarin.Forms.Platform.Android.VisualElementPackager.AddChild (Xamarin.Forms.VisualElement view, Xamarin.Forms.Platform.Android.IVisualElementRenderer oldRenderer, Xamarin.Forms.Platform.Android.RendererPool pool, System.Boolean sameChildren) [0x000b3] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementPackager.cs:140 
  at Xamarin.Forms.Platform.Android.VisualElementPackager.SetElement (Xamarin.Forms.VisualElement oldElement, Xamarin.Forms.VisualElement newElement) [0x00163] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementPackager.cs:351 
  at Xamarin.Forms.Platform.Android.VisualElementPackager.Load () [0x00000] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementPackager.cs:112 
  at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].SetPackager (Xamarin.Forms.Platform.Android.VisualElementPackager packager) [0x00007] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:481 
  at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].SetElement (TElement element) [0x000e8] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:244 
  at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].Xamarin.Forms.Platform.Android.IVisualElementRenderer.SetElement (Xamarin.Forms.VisualElement element) [0x00033] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:131 
  at Xamarin.Forms.Platform.Android.Platform.CreateRenderer (Xamarin.Forms.VisualElement element, Android.Content.Context context) [0x0003e] in D:\a\1\s\Xamarin.Forms.Platform.Android\Platform.cs:358 
  at Xamarin.Forms.Platform.Android.VisualElementPackager.AddChild (Xamarin.Forms.VisualElement view, Xamarin.Forms.Platform.Android.IVisualElementRenderer oldRenderer, Xamarin.Forms.Platform.Android.RendererPool pool, System.Boolean sameChildren) [0x000b3] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementPackager.cs:140 
  at Xamarin.Forms.Platform.Android.VisualElementPackager.SetElement (Xamarin.Forms.VisualElement oldElement, Xamarin.Forms.VisualElement newElement) [0x00163] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementPackager.cs:351 
  at Xamarin.Forms.Platform.Android.VisualElementPackager.Load () [0x00000] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementPackager.cs:112 
  at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].SetPackager (Xamarin.Forms.Platform.Android.VisualElementPackager packager) [0x00007] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:481 
  at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].SetElement (TElement element) [0x000e8] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:244 
  at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].Xamarin.Forms.Platform.Android.IVisualElementRenderer.SetElement (Xamarin.Forms.VisualElement element) [0x00033] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:131 
  at Xamarin.Forms.Platform.Android.Platform.CreateRenderer (Xamarin.Forms.VisualElement element, Android.Content.Context context) [0x0003e] in D:\a\1\s\Xamarin.Forms.Platform.Android\Platform.cs:358 
  at Xamarin.Forms.Platform.Android.VisualElementPackager.AddChild (Xamarin.Forms.VisualElement view, Xamarin.Forms.Platform.Android.IVisualElementRenderer oldRenderer, Xamarin.Forms.Platform.Android.RendererPool pool, System.Boolean sameChildren) [0x000b3] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementPackager.cs:140 
  at Xamarin.Forms.Platform.Android.VisualElementPackager.SetElement (Xamarin.Forms.VisualElement oldElement, Xamarin.Forms.VisualElement newElement) [0x00163] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementPackager.cs:351 
  at Xamarin.Forms.Platform.Android.VisualElementPackager.Load () [0x00000] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementPackager.cs:112 
  at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].SetPackager (Xamarin.Forms.Platform.Android.VisualElementPackager packager) [0x00007] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:481 
  at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].SetElement (TElement element) [0x000e8] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:244 
  at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].Xamarin.Forms.Platform.Android.IVisualElementRenderer.SetElement (Xamarin.Forms.VisualElement element) [0x00033] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:131 
  at Xamarin.Forms.Platform.Android.Platform.CreateRenderer (Xamarin.Forms.VisualElement element, Android.Content.Context context) [0x0003e] in D:\a\1\s\Xamarin.Forms.Platform.Android\Platform.cs:358 
  at Xamarin.Forms.Platform.Android.AppCompat.Platform.AddChild (Xamarin.Forms.Page page, System.Boolean layout) [0x0000d] in D:\a\1\s\Xamarin.Forms.Platform.Android\AppCompat\Platform.cs:387 
  at Xamarin.Forms.Platform.Android.AppCompat.Platform.SetPageInternal (Xamarin.Forms.Page newRoot) [0x0005a] in D:\a\1\s\Xamarin.Forms.Platform.Android\AppCompat\Platform.cs:345 
  at Xamarin.Forms.Platform.Android.AppCompat.Platform.SetPage (Xamarin.Forms.Page newRoot) [0x000e6] in D:\a\1\s\Xamarin.Forms.Platform.Android\AppCompat\Platform.cs:299 
  at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.InternalSetPage (Xamarin.Forms.Page page) [0x00039] in D:\a\1\s\Xamarin.Forms.Platform.Android\AppCompat\FormsAppCompatActivity.cs:508 
  at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.SetMainPage () [0x00000] in D:\a\1\s\Xamarin.Forms.Platform.Android\AppCompat\FormsAppCompatActivity.cs:534 
  at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.LoadApplication (Xamarin.Forms.Application application) [0x00140] in D:\a\1\s\Xamarin.Forms.Platform.Android\AppCompat\FormsAppCompatActivity.cs:193 
  ... (Removed)
  at Android.App.Activity.n_OnCreate_Landroid_os_Bundle_ (System.IntPtr jnienv, System.IntPtr native__this, System.IntPtr native_savedInstanceState) [0x00010] in /Users/builder/azdo/_work/1/s/xamarin-android/src/Mono.Android/obj/Release/monoandroid10/android-31/mcw/Android.App.Activity.cs:2781 
  at (wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.7(intptr,intptr,intptr)

Screenshots

Do you have any suggestions or corrections?
Maybe I’m wrong about the implementation of CollectionView.

Answer 1 · 2022-03-08T09:49:18.000Z

https://github.com/roubachof/Sharpnado.CollectionView#initialization

I also suggest you to use the TaskLoaderView instead of StateLayout.
It is specialized for view model loading.

Answer 2 · 2022-03-08T09:55:29.000Z

I have correctly initilized the nuget package, the problem is showing after initialization.
I already think of using TaskLoaderView instead of StateLayout but in a second moment.

Xamarin.Forms.App:

Android:

iOS:

Answer 3 · 2022-03-08T10:01:13.000Z

roubachof commented 2 years ago

Answer 4 · 2022-03-08T10:04:10.000Z

I see in this moment the line "Initializer.Initilize" in the specified project.
I’m sorry I didn’t look.
I thought it was a line for another nuget, and I didn’t notice.

Thank you so much for the correction and the immediate response.