Question: Is there any option to bring a specific index into view in a ListView?

[w-ahmad]

First asked at community call chat but couldn't get answer or workaround. #9653 (comment)

When dealing with a ListView containing duplicate items in its ItemsSource, there isn't a direct method to specifically bring a duplicate item into view. For instance, if an item appears at index 30 and again at index 100, the challenge is how to scroll to the item at index 100. The commonly known method ListViewBase.ScrollIntoView(object item) will default to the item at index 30, not the one at index 100.

Manually calculating offset to a specific index is not possible when the items are of variable in size because all the containers are not initialized at once.

Test App: https://github.com/w-ahmad/ListViewScrollTest

[castorix]

If I do this, it scrolls to index 100 :

   var item = lv1.Items[100];
   lv1.ScrollIntoView(item);
   lv1.SelectedItem = item;

[w-ahmad]

In the example the items are not duplicate I guess, the problem happens only when there are duplicate items in the ItemsSource. Here is a test application that demonstrates the problem: https://githu6b.com/w-ahmad/ListViewScrollTest

[castorix]

In the example the items are not duplicate I guess, the problem happens only when there are duplicate items in the ItemsSource. Here is a test application that demonstrates the problem: https://githu6b.com/w-ahmad/ListViewScrollTest

Right.
But to select the right item, I added a "hidden" index in the ObservableCollection of the ItemsSource (a field not displayed in the ListView)

[w-ahmad]

Adding a hidden index to the data item is one method, and there could be other ways to address it. As I am facing this in a control distributed via the NuGet Package, I cannot dictate what users will set as the ItemsSource. The control is WinUI.TableView, derived from ListView, and to let user select cells, I must scroll rows according to the selected cell.

[w-ahmad]

Would be very grateful if someone could suggest a solution or workaround.

[HHaoWang]

The problem of adding index numbers to list items view is very classic and still lacks a good solution after all these years. This need exists not only for ListView but also for various other collection controls. When I developed native Android apps, I was surprised by the implementation of RecyclerView, although its MVVM isn't as powerful as XAML, it's surprisingly simple to implement sequential numbering. Why not consider implementing this feature in first-party solutions?

[w-ahmad]

I found the internal implementation of ScrollIntoView method that is part of Selector class.

microsoft-ui-xaml/src/dxaml/xcp/dxaml/lib/Selector_Partial.cpp

Line 3103 in 66a7b0a

Selector::ScrollIntoViewInternal(

The method accepts item object as the parameter, but it fetches the index of the given item from Items to pass to the next method.

microsoft-ui-xaml/src/dxaml/xcp/dxaml/lib/Selector_Partial.cpp

Line 3152 in 66a7b0a

IFC(spItems.Cast<ItemCollection>()->IndexOf(item, &index, &found));

The next method takes the index of item and do the stuff to bring it into view. It seems feasible to introduce a method in the ListViewBase class that would accept the item's index rather than the item itself.
@ranjeshj

[w-ahmad]

added it to the feature request #9890