Forum Xamarin Xamarin.Forms

Can I bind to a command from a ListView's parent when I'm using ViewCells in a separate file?

UnreachableCodeUnreachableCode USMember ✭✭✭
edited March 2019 in Xamarin.Forms

My app needs to switch between two different ViewCells, so I've been using a DataTemplateSelector for this like so:

using MyOrg.PageModels;
using Xamarin.Forms;

namespace MyOrg.ViewCells
    public class ItemDataTemplateSelector : DataTemplateSelector
        public ItemDataTemplateSelector()
            // Retain instances 
            SimpleTemplate = new DataTemplate(typeof(SimpleItemViewCell));
            DetailedTemplate = new DataTemplate(typeof(DetailedItemViewCell));

        protected override DataTemplate OnSelectTemplate(object item, BindableObject container)
            return ((MyPageModel)container.BindingContext).SimpleModeEnabled ? SimpleTemplate : DetailedTemplate;

        private readonly DataTemplate SimpleTemplate;
        private readonly DataTemplate DetailedTemplate;

The issue now is that when creating these cells in the constructor, it's using the ViewCells from separate files to the actual page:

 <ViewCell xmlns="" 
     <Frame CornerRadius="2.5"
             Margin="5, 2.5"
             Padding="10" >
         <StackLayout Orientation="Horizontal">
             <Label Text="{Binding Number}" 
                    TextColor="{StaticResource MidBlue}" 
                    FontSize="Large" />
             <Label Text="{Binding DetailText}" 
                   Command="{Binding Path=ParentBindingContext.DeleteSelectedCommand, Source={x:Reference MyPageName}}"

MyPageName refers to the name of my page from a content page file. But I don't have access to this from this separate file, so the command doesn't fire.

Is there any way I can pass a reference to the page into each of these ViewCells?

Best Answer


  • UnreachableCodeUnreachableCode USMember ✭✭✭
    edited March 2019

    @LandLu this works great. My command is now firing. I needed to pass the item into the command so that I could delete it. Here's what I came up with that built on your approach in the SimpleItemViewCell by overriding OnBindingContextChanged. I'm not sure if it's the best approach as I have to retain the cell and the menu item which seems a bit clumsy to me.

    static void ReferencedPageChanged(object bindableObject, object oldValue, object newValue)
        if (newValue != null)
            menuItem = new MenuItem();
            menuItem.Icon = "sharp_delete_white_24.png";
            menuItem.SetBinding(MenuItem.CommandProperty, new Binding("DeleteSelectedCommand", source: newValue));
            simpleViewCell = bindableObject as ViewCell;
     protected override void OnBindingContextChanged()
         if (BindingContext != null)
             menuItem.SetBinding(MenuItem.CommandParameterProperty, new Binding("BindingContext", source: this));
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