MAUI: Enhanced listview for iOS plaform

Question

I have an enhanced listview (Helpers) which is working fine on Xamarin Forms project. But when I migrate it to MAUI my app is breaking with below exception.

System.NullReferenceException: Object reference not set to an instance of an object. at Microsoft.Maui.Controls.Compatibility.Platform.iOS.CellTableViewCell.GetNativeCell(UITableView , Cell , Boolean , String ) at Microsoft.Maui.Controls.Compatibility.Platform.iOS.ListViewRenderer.ListViewDataSource.GetCell(UITableView , NSIndexPath ) at UIKit.UIApplication.UIApplicationMain(Int32 , String[] , IntPtr , IntPtr ) at UIKit.UIApplication.Main(String[] , Type , Type ) at MyProject.Program.Main(String[] args) in /Users/MyCompany/Projects/MyProject-maui/MyProject/Platforms/iOS/Program.cs:line 13

Screenshot

My Code:

SingleProject

public class EnhancedListView : ListView
{
    public EnhancedListView()
    {
    }
    public void ForceNativeTableUpdate()
    {
        ViewCellSizeChangedEvent?.Invoke();
    }
    public event Action ViewCellSizeChangedEvent;
}

iOS Platform

class EnhancedListViewRenderer : ListViewRenderer
{
    protected override void OnElementChanged(ElementChangedEventArgs<ListView> e)
    {
        base.OnElementChanged(e);
        if (e.NewElement is EnhancedListView enhancedListView)
        {
            enhancedListView.ViewCellSizeChangedEvent += UpdateTableView;
        }
        if(Control != null)
        {
            Control.SectionHeaderTopPadding = new nfloat(0);
        }
    }
    private void UpdateTableView()
    {
        if (!(Control is UITableView tv)) return;
        tv.BeginUpdates();
        tv.EndUpdates();
    }
}

Android part is working fine without any enhanced renderers. It is expanding and collapsing when data is visible on the UI.

Answer 1

Hello,

Thanks for your feedback.

After testing, your code will work fine on iOS. Therefore, the cause of this issue is more likely to be an issue with the development tool.

In addition, using the Renderer in MAUI should comply with the specifications in this document.

• Reuse custom renderers in .NET MAUI.

Best Regards,

Alec Liu.

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Answer 2

I faced with the same issue. After some investigation I found out that there are two ListViewRenderer classes. I used the Microsoft.Maui.Controls.Compatibility.Platform.iOS.ListViewRenderer as a base for my own renderer - and it causes an error. When I changed it to the Microsoft.Maui.Controls.Handlers.Compatibility.ListViewRenderer, the error was gone.