Error in adding footer to ListView in .Net MAUI

Question

Error in adding footer to ListView in .Net MAUI

TD D 5

HI all,
Please help as this error cites on code line: listView.Footer = footer;
 as below:
Java.Lang.IllegalStateException
  Message=The specified child already has a parent. You must call removeView() on the child's parent first.
when adding a new footer of BoxView to ListView in .Net MAUI?

in .Net MAUI project  in call:                         // Create a footer view with a transparent background

Anonymous

Hi @TD D , Welcome to Microsoft Q&A,

I am not an expert in .Net Maui, you can try the following code to see if it can solve your problem.

Please let me know if it's useful and I'll turn it into an answer.

// Create a BoxView for your footer
BoxView footer = new BoxView
{
    BackgroundColor = Color.Transparent, // Set your desired background color
    HeightRequest = 50 // Set the desired height of the footer
};

// Check if the footer already has a parent
if (footer.Parent != null)
{
    // If it has a parent, remove it from the parent
    (footer.Parent as Layout<View>)?.Children.Remove(footer);
}

// Set the ListView's footer to the new footer
listView.Footer = footer;

TD D 5

HI, As footer.Parent returns null, then (footer.Parent as Layout<View>)?.Children.Remove(footer); is not run. So the next code: listView.Footer = footer; will cite error:

Java.Lang.IllegalStateException
  Message=The specified child already has a parent. You must call removeView() on the child's parent first.
I do not understand in .Net MAI we create a new BoxView, and why this BoxView has a  parent inside? And Microsoft does not clearly hint code to remove parent, or add the optional parameter to BoxView constructor to automatically remove the parent, if any

TD D 5

Hi all,

Please help resolving the error:

Microsoft.Maui.Platform.HandlerNotFoundException
  Message=Handler not found for view SkiaSharp.Views.Maui.Controls.SKCanvasView.
  Source=Microsoft.Maui
When using SkiaSharp libary in .Net MAUI project as a processing of converting Xamarin Forms code to .Net MAUI code? Thanks

Yonglun Liu (Shanghai Wicresoft Co,.Ltd.) 50,126 Reputation points Microsoft External Staff

2023-09-11T01:54:49.15+00:00
For further investigation, could you please provide the following information?

The MAUI SDK version.

What is the platform on which your program runs?

Could you please update the issue with a minimal snippet that can reproduce this issue?

What is your expected behavior, and what is the actual behavior of the program at the moment? What are the differences between them?

Please refer to Guidelines for posting a quality question on Microsoft Q&A for more details.
TD D 5 Reputation points

2023-09-13T13:19:14.9066667+00:00
Hi,

Thanks for the answer. For fast answer as this is common issue of Xamarin Forms/ .Net MAUI converting process, I shortens the issue. So please see my detailed reply as below:

The MAUI SDK version
MAUI SDK for Android 13.0

What is the platform on which your program runs?
The Android/ iOS platforms are built

Could you please update the issue with a minimal snippet that can reproduce this issue?
I am converting from Xamarin Forms code to .Net MAUI one. The code regarding SkiaSharp library usage such as:

_canvasView = new SKCanvasView(); _canvasView.PaintSurface += OnCanvasViewPaintSurface; Content = _canvasView;,

runs well in Xamarin Forms, but it fails in .Net MAUI. OnCanvasViewPaintSurface is never called in .Net MAUI

What is your expected behavior, and what is the actual behavior of the program at the moment? What are the differences between them?

All the code running well in Xamarin Forms should be executed w/o any error in .Net MAUI. I have to modify a lot to allow it run in .Net MAUI. For example, if you define a Grid and another custom control, then add them to a AbsoluteLayout, before assigning this absolutelayout as child to ScrollView with Orientation = ScrollOrientation.Both, then this grid is not visible on screen in .Net MAUI, although in Xamarin Forms, this grid is displayed perfectly. Removing Orientation = ScrollOrientation.Both from Scrollview definition, the gird is showed in .Net MAUI. It took me many days to find down this interesting issue. Considering SkCanvasView cannot be used in my .Net MAUI app (.Net 7.0) I am now changing code to use GraphicView instead
Yonglun Liu (Shanghai Wicresoft Co,.Ltd.) 50,126 Reputation points Microsoft External Staff

2023-09-18T01:03:49.8833333+00:00

May I know whether your issue has been solved or not? If you're still having problems, please explain in detail what is still going wrong and what you need help with.

2 answers

Your answer

Anonymous

2023-09-08T12:42:02.8833333+00:00

Hi @TD D , Welcome to Microsoft Q&A,

I am not an expert in .Net Maui, you can try the following code to see if it can solve your problem.

Please let me know if it's useful and I'll turn it into an answer.

// Create a BoxView for your footer BoxView footer = new BoxView { BackgroundColor = Color.Transparent, // Set your desired background color HeightRequest = 50 // Set the desired height of the footer }; // Check if the footer already has a parent if (footer.Parent != null) { // If it has a parent, remove it from the parent (footer.Parent as Layout<View>)?.Children.Remove(footer); } // Set the ListView's footer to the new footer listView.Footer = footer;
TD D 5 Reputation points

2023-09-09T00:19:52.88+00:00

HI, As footer.Parent returns null, then (footer.Parent as Layout<View>)?.Children.Remove(footer); is not run. So the next code: listView.Footer = footer; will cite error:

Java.Lang.IllegalStateException Message=The specified child already has a parent. You must call removeView() on the child's parent first. I do not understand in .Net MAI we create a new BoxView, and why this BoxView has a parent inside? And Microsoft does not clearly hint code to remove parent, or add the optional parameter to BoxView constructor to automatically remove the parent, if any
TD D 5 Reputation points

2023-09-09T03:54:49.07+00:00

Hi all,

Please help resolving the error:

Microsoft.Maui.Platform.HandlerNotFoundException Message=Handler not found for view SkiaSharp.Views.Maui.Controls.SKCanvasView. Source=Microsoft.Maui When using SkiaSharp libary in .Net MAUI project as a processing of converting Xamarin Forms code to .Net MAUI code? Thanks
Yonglun Liu (Shanghai Wicresoft Co,.Ltd.) 50,126 Reputation points Microsoft External Staff

2023-09-11T01:54:49.15+00:00

For further investigation, could you please provide the following information?

The MAUI SDK version.

What is the platform on which your program runs?

Could you please update the issue with a minimal snippet that can reproduce this issue?

What is your expected behavior, and what is the actual behavior of the program at the moment? What are the differences between them?

Please refer to Guidelines for posting a quality question on Microsoft Q&A for more details.
TD D 5 Reputation points

2023-09-13T13:19:14.9066667+00:00

Hi,

Thanks for the answer. For fast answer as this is common issue of Xamarin Forms/ .Net MAUI converting process, I shortens the issue. So please see my detailed reply as below:

The MAUI SDK version
MAUI SDK for Android 13.0

What is the platform on which your program runs?
The Android/ iOS platforms are built

Could you please update the issue with a minimal snippet that can reproduce this issue?
I am converting from Xamarin Forms code to .Net MAUI one. The code regarding SkiaSharp library usage such as:

_canvasView = new SKCanvasView(); _canvasView.PaintSurface += OnCanvasViewPaintSurface; Content = _canvasView;,

runs well in Xamarin Forms, but it fails in .Net MAUI. OnCanvasViewPaintSurface is never called in .Net MAUI

What is your expected behavior, and what is the actual behavior of the program at the moment? What are the differences between them?

All the code running well in Xamarin Forms should be executed w/o any error in .Net MAUI. I have to modify a lot to allow it run in .Net MAUI. For example, if you define a Grid and another custom control, then add them to a AbsoluteLayout, before assigning this absolutelayout as child to ScrollView with Orientation = ScrollOrientation.Both, then this grid is not visible on screen in .Net MAUI, although in Xamarin Forms, this grid is displayed perfectly. Removing Orientation = ScrollOrientation.Both from Scrollview definition, the gird is showed in .Net MAUI. It took me many days to find down this interesting issue. Considering SkCanvasView cannot be used in my .Net MAUI app (.Net 7.0) I am now changing code to use GraphicView instead
Yonglun Liu (Shanghai Wicresoft Co,.Ltd.) 50,126 Reputation points Microsoft External Staff

2023-09-18T01:03:49.8833333+00:00

May I know whether your issue has been solved or not? If you're still having problems, please explain in detail what is still going wrong and what you need help with.

Answer 1

Hello,

Thanks for your feedback.

After testing, the width and height properties needed to be set for the _canvasView to trigger the OnCanvasViewPaintSurface event.

Please refer to the following code snippet:

<skia:SKCanvasView x:Name="canvasView"
                               HeightRequest="500" WidthRequest="340"/>

Best Regards,

Alec Liu.

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Answer 2

Brian Runck 0

FWIW, this specific problem is a known issue: https://github.com/dotnet/maui/issues/16043

Ignore the part about the Flyout page; the problem is the ListView on the page.

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Error in adding footer to ListView in .Net MAUI

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