Question

I need to do some stuff when my ListView is finished displaying the items.
As it is now I call the NotifyDataSetChanged and then use the list.FirstVisiblePosition but the problem is that no items are visible at the time being called.

So how can I trigger my code when items are visible on screen?

The reason for this is that I need to do some work only for the visible items.

Thanks, Nicklas

Answer 1

What collection type are you using with the ListView? If you’re using a “normal” collection type (e.g. System.Collections.Generic.List<T>), then the ListView won’t see any items you add to the collection after the ListView is constructed. You would need to use JavaList<T> instead.

See the example at the end of the Collections binding overview:

// This fails:
var badSource  = new List<int> { 1, 2, 3 };
var badAdapter = new ArrayAdapter<int>(context, textViewResourceId, badSource);
badAdapter.Add (4);
if (badSource.Count != 4) // true
    throw new InvalidOperationException ("this is thrown");

// this works:
var goodSource  = new JavaList<int> { 1, 2, 3 };
var goodAdapter = new ArrayAdapter<int> (context, textViewResourceId, goodSource);
goodAdapter.Add (4);
if (goodSource.Count != 4) // false
    throw new InvalidOperaitonException ("should not be reached.");