Xamarin表单元素父属性为null

Question

I have a ViewCell that is used as an item template for a ListView :

ListView details_list = new ListView ();
details_list.ItemTemplate = new DataTemplate(typeof(CartViewCell));

Inside the ViewCell I would like to have a function to access the ListView's itemSource in order to delete an item. I though I would do this by accessing the Parent property inside the ViewCell

ListView parent = (ListView)this.Parent;

But when I attempt this, it shows the parent to be null. Is this an incorrect way to be using the Parent property? What am I missing?

Answer 1

there is an override method you have to call it then the parent will not be null

protected override void OnParentSet()
        {
            object view = Parent;
            base.OnParentSet();

            if (view.GetType() == typeof(Grid))
            {

            }
        }

Answer 2

There are a couple of ways to solve this; two possibilities include

1. Use a Command

Define a Command in your ViewModel,

// define a command property
public ICommand DeleteCommand { get; set; }

// in your constructor, initialize the command
DeleteCommand = new Command<string>((id) =>
{
  // do the appropriate delete action here
}

and then in your ViewCell bind to it

<Button Command="{Binding DeleteCommand}" CommandParameter="{Binding ID}" Text="Delete" />

2. Use message passing

In your ViewModel, subscribe to a message:

MessagingCenter.Subscribe<MyViewCell, string> (this, "Delete", (sender, id) => {
    // do the appropriate delete action here
});

In your ViewCell, send the message whenever they click the button (or whatever triggers the action) - ID should be and identifier for the particular item

MessagingCenter.Send<MyViewCell, string> (this, "Delete", ID);