[iOS] ListView Header/HeaderTemplate changes DataContext incorrectly

[Soap-141]

Current behavior

Using ListView.HeaderTemplate makes the application crash on iOS and ListView.Header is not working at all.

Expected behavior

The ListView.HeaderTemplate and ListView.Header properties should work.

How to reproduce it (as minimally and precisely as possible)

1. Download ListViewHeader.zip
2. Start the application on Windows or Android
3. Notice it works
4. Start the application on iOS
5. Notice it crashes, does nothing or has a black screen.

Workaround

N/A

Works on UWP/WinUI

Yes

Environment

Uno.WinUI / Uno.WinUI.WebAssembly / Uno.WinUI.Skia

NuGet package version(s)

Latest stable.

Affected platforms

iOS

IDE

Visual Studio 2022

IDE version

17.6.5

Relevant plugins

No response

Anything else we need to know?

No response

[Soap-141]

https://github.com/unoplatform/tradezero-private/issues/6

[Soap-141]

@jeromelaban I just tried using latest Uno 5 release and it's still an issue.

[Soap-141]

@takla21 can you link the backport that caused this into 4.9 please?

[jeromelaban]

@Soap-141 the issue you're facing for the sample you built is #212, and it's caused by this.DataContext = this.

If you move all the DataContext in a separate class, the header is shown and the binding works with 4.9.45.

I'm closing this issue, but feel free to reopen if you have a specific behavior that is incorrect.

---

Here's the updated sample:

public sealed partial class MainPage : Page
{
	Model _model = new();

        public MainPage()
	{
		this.InitializeComponent();
		this.DataContext = _model;

        }

	private void Button_Click(object sender, RoutedEventArgs e)
	{
		_ = Frame.Navigate(typeof(TestPage));
	}

	private void Button_Click_1(object sender, RoutedEventArgs e)
	{
		_model.ListViewHeader.SimpleBinding += 1;
	}
}

public class Model
{
        public List<int> Source { get; } = new List<int>();

        public ListViewHeader ListViewHeader { get; } = new ListViewHeader();
}

[Soap-141]

@jeromelaban Main issue that I'm trying to reproduce right now is that my Header DataContext is becoming null after navigation. Think it has been introduced by this https://github.com/unoplatform/uno/pull/12939/files because it wasn't happening before 4.9.45.

GitHub

fix(listview): Adjust datacontext for header/footer for ListView by jeromelaban · Pull Request #12939 · unoplatform/uno

GitHub Issue (If applicable): closes unoplatform/tradezero-private#8, fixes unoplatform/tradezero-private#6 PR Type What kind of change does this PR introduce?

Bugfix

What is the new behavior?
Ap...

[Soap-141]

@jeromelaban Tagged you as asked in meeting. I will also send you a private StackTrace that I manually logged.

[Soap-141]

@jeromelaban This issue is not really updated with what we talked about behind the scenes and also not working for that client anymore but if they mentions it you know what it is.

[jeromelaban]

We're not able to reproduce the issue (neither with Uno 4.10.13, nor 5.0.0-dev.2656), even when navigating from one page to another. An additional test which adds and removes the ListView from the tree is still not causing the DataContext to be incorrect.

@Epsil0neR if you are able to augment this new repro to show the behavior you're getting, it will be useful, thanks!

[jeromelaban]

This issue is fixed in 4.10.34, 5.0 latest, available on nuget.