Horizontal ScrollView for (Xamarin) Android using RecyclerView and GridLayoutManager

gistfile1.txt

  //MainActivity's private vars and key methods:
  public class MainActivity : FragmentActivityBase
  {
        private RecyclerView _recyclerViewPhotosTakenEdit;
        private IList<PhotoItemModel> _photoItemsModel;
        private RecyclerView.LayoutManager _layoutManager;
        private PhotoQuestionRecyclerAdapter _photoQuestionImageAdapter;
        ......
  }
  
  private void AttachControlls()
  {
      _recyclerViewPhotosTakenEdit = FindViewById<RecyclerView>(Resource.Id.recyclerViewPhotoQuestionImagesEdit);
      _layoutManager = new GridLayoutManager(this, 1, GridLayoutManager.Horizontal, false);
      _recyclerViewPhotosTakenEdit.SetLayoutManager(_layoutManager);
  }
  
  private void PopulateRecyclerViewAdapterData()
  {
       _photoQuestionImageAdapter = new PhotoQuestionRecyclerAdapter(this, _photoItemsModel, false);  
       _recyclerViewPhotosTakenEdit.SetAdapter(_photoQuestionImageAdapter);
  }
  
  //PhotoQuestionRecyclerAdapter code:
  
   public class PhotoQuestionRecyclerAdapter : RecyclerView.Adapter 
    {
        public event EventHandler<int> ItemClick;
        private readonly Activity _context;
        private readonly IList<PhotoItemModel> _photoItems;
        private readonly bool _showSelected;
   
        public PhotoQuestionRecyclerAdapter(Activity context, IList<PhotoItemModel> photoItems, bool showSelected = true)
        {
            _context = context;
            _photoItems = photoItems;
            _showSelected = showSelected;
        }

        public override void OnBindViewHolder(RecyclerView.ViewHolder holder, int position)
        {
            if (!_photoItems.Any()) return;

            if (holder != null)
            {
                var photoItemModel = _photoItems[position];
                (holder as PhotoItemViewHolder).ImageDescriptionTextView.SetText(photoItemModel.PhotoItem.Description,
                    TextView.BufferType.Normal);
                (holder as PhotoItemViewHolder).ImageView.SetImageBitmap(
                    BitmapFactory.DecodeByteArray(photoItemModel.PhotoItem.Image, 0,
                        photoItemModel.PhotoItem.Image.Length));
                if (_showSelected)
                    (holder as PhotoItemViewHolder).ImageSelectedCheckBox.Selected = photoItemModel.Selected;
            }
        }

        public override RecyclerView.ViewHolder OnCreateViewHolder(ViewGroup parent, int viewType)
        {
            View view = LayoutInflater.From(parent.Context)
            .Inflate(Resource.Layout.RecyclerViewItemTemplate, parent, false);
            PhotoItemViewHolder photoItemViewHolder = new PhotoItemViewHolder(view, OnClick, _photoItems, _showSelected);
            return photoItemViewHolder;
        }

        void OnClick(int position)
        {
            ItemClick?.Invoke(this, position);
        }

        public override int ItemCount => _photoItems.Count;

        public void ToggleItemSelection(int position, RecyclerView currentView)
        {
            var photoItemModel = _photoItems[position];
         
            photoItemModel.Selected = !photoItemModel.Selected;

            var viewHolder = currentView?.FindViewHolderForAdapterPosition(position) as PhotoItemViewHolder;

            if (viewHolder != null && _showSelected)
            {
                viewHolder.ImageSelectedCheckBox.Checked = photoItemModel.Selected;
                ((ApplicationGlobal)_context.ApplicationContext).PhotoItemsModel = _photoItems;
            }
        }
    }

    public class PhotoItemViewHolder : RecyclerView.ViewHolder
    {
        private readonly IList<PhotoItemModel> _items;
        public ImageView ImageView { get; set; }
        public CheckBox ImageSelectedCheckBox { get; set; }

        public TextView ImageDescriptionTextView { get; set; }

        public PhotoItemViewHolder(View view, Action<int> listener, IList<PhotoItemModel> items, bool showSelected) : base(view)
        {
            _items = items;
            ImageDescriptionTextView = (TextView)view.FindViewById(Resource.Id.textViewRecyclerViewTemplateImageDescription);          
            ImageView = view.FindViewById<ImageView>(Resource.Id.imageViewRecyclerViewTemplateImage);     
            ImageSelectedCheckBox = view.FindViewById<CheckBox>(Resource.Id.checkBoxRecyclerViewTemplateSelected);
            ImageSelectedCheckBox.Visibility = !showSelected ? ViewStates.Invisible : ViewStates.Visible;

            view.Click += (sender, args) => listener(AdapterPosition);
        }
    }