SetAppThemeColor crashes with NRE

[AlleSchonWeg]

Description

Hi,
i updated to a new Nightly and now my app crashes.
This worked in Version="8.0.20-nightly.10298" but crashes in Version="8.0.20-nightly.10394"

Steps to Reproduce

I can repro the crash with this minimal demo:

	public class Test : BindableObject {
		public static readonly BindableProperty IconColorProperty = BindableProperty.Create(
								propertyName: nameof(IconColor),
								returnType: typeof(Color),
								declaringType: typeof(Test),
								defaultValue: null,
								defaultBindingMode: BindingMode.TwoWay);

		public Color IconColor {
			get => (Color)GetValue(IconColorProperty);
			set => SetValue(IconColorProperty, value);
		}
	}

And then do this:

				var test = new Test();
				test.SetAppThemeColor(Test.IconColorProperty, Colors.Red, Colors.Blue);

I receive a crash:

at Microsoft.Maui.Controls.AppThemeBinding.AppThemeProxy..ctor(Element parent, AppThemeBinding binding) in D:\a_work\1\s\src\Controls\src\Core\AppThemeBinding.cs:line 19
at Microsoft.Maui.Controls.AppThemeBinding.Apply(Object context, BindableObject bindObj, BindableProperty targetProperty, Boolean fromBindingContextChanged, SetterSpecificity specificity) in D:\a_work\1\s\src\Controls\src\Core\AppThemeBinding.cs:line 74
at Microsoft.Maui.Controls.BindableObject.SetBinding(BindableProperty targetProperty, BindingBase binding, SetterSpecificity specificity) in D:\a_work\1\s\src\Controls\src\Core\BindableObject.cs:line 332
at Microsoft.Maui.Controls.BindableObject.SetBinding(BindableProperty targetProperty, BindingBase binding) in D:\a_work\1\s\src\Controls\src\Core\BindableObject.cs:line 288
at Microsoft.Maui.Controls.BindableObjectExtensions.SetAppTheme[Color](BindableObject self, BindableProperty targetProperty, Color light, Color dark) in D:\a_work\1\s\src\Controls\src\Core\BindableObjectExtensions.cs:line 125
at Microsoft.Maui.Controls.BindableObjectExtensions.SetAppThemeColor(BindableObject self, BindableProperty targetProperty,

Link to public reproduction project repository

No response

Version with bug

Nightly / CI build (Please specify exact version)

Is this a regression from previous behavior?

Yes, this used to work in .NET MAUI

Last version that worked well

Unknown/Other

Affected platforms

Android

Affected platform versions

No response

Did you find any workaround?

No response

Relevant log output

No response

[StephaneDelcroix]

the problem is that Test is a BindableObject and not an Element. I can prevent the crash to happen, but you won't get the AppTheme working on it as it's not parented

[AlleSchonWeg]

Hi @StephaneDelcroix
the Test class items are the items in a collection. I create this collection in a viewmodel (implement INotifyPropertyChanged) and after creation i invoke the PropertyChanged event. Like this:

internal async Task CreateAsync() {
		_ items = new ObservableCollection<Test>()
		var test = new Test();
		test.SetAppThemeColor(Test.IconColorProperty, Colors.Red, Colors.Blue);
		_items.Add(test);
		//Add more to collection 
		PropertyChanged.Invoke(this, new PropertyChangedEventArgs(nameof(Items)));
}
public ObservableCollection<Test> Items {
		get { return _items; }
}

This collection (Items property) is the ItemsSource from a ListView. My goal is if a user changed the theme (dark/light) and the app is running that the color is changing at runtime.
This works well in Xamarin Forms and if i remember correctly it also works in earlier nightly builds.

Edit:
I downgraded the nightly and i can confirm that changing between dark and light mode (via system settings) my icons in the list are changing the colour.

[StephaneDelcroix]

Well, that no longer works. Theme propagation is now done through Parenting.

You can still subscribe to the AppThemeChanged event yourself, or parent your elements

[AlleSchonWeg]

Hi @StephaneDelcroix

with the nightly 10423 the NRE is gone. But now another exeption happens when i change the theme vie system settings:

System.InvalidOperationException: 'Collection was modified; enumeration operation may not execute.'

StackTrace:

0xFFFFFFFFFFFFFFFF in Android.Runtime.RuntimeNativeMethods.monodroid_debugger_unhandled_exception C# Annotated Frame
0x1A in Android.Runtime.JNINativeWrapper.unhandled_exception at /Users/runner/work/1/s/xamarin-android/src/Mono.Android/Android.Runtime/JNINativeWrapper.g.cs:13,5 C# Annotated Frame
0x1E in Android.Runtime.JNINativeWrapper.Wrap_JniMarshal_PPL_V at /Users/runner/work/1/s/xamarin-android/src/Mono.Android/Android.Runtime/JNINativeWrapper.g.cs:126,26 C# Annotated Frame
0xA in System.ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumFailedVersion C# Annotated Frame
0x13 in System.Collections.Generic.List<System.Action<object,Microsoft.Maui.Controls.Internals.ResourcesChangedEventArgs>>.Enumerator.MoveNextRare C# Annotated Frame
0x4B in System.Collections.Generic.List<System.Action<object,Microsoft.Maui.Controls.Internals.ResourcesChangedEventArgs>>.Enumerator.MoveNext C# Annotated Frame
0x2F in Microsoft.Maui.Controls.Element.OnResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\Element\Element.cs:648,64 C# Annotated Frame
0x2 in Microsoft.Maui.Controls.Element.OnParentResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\Element\Element.cs:623,4 C# Annotated Frame
0x1B in Microsoft.Maui.Controls.VisualElement.OnParentResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\VisualElement\VisualElement.cs:1446,5 C# Annotated Frame
0x16 in Microsoft.Maui.Controls.Element.OnParentResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\Element\Element.cs:618,5 C# Annotated Frame
0x28 in Microsoft.Maui.Controls.Element.OnResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\Element\Element.cs:649,6 C# Annotated Frame
0x2 in Microsoft.Maui.Controls.Element.OnParentResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\Element\Element.cs:623,4 C# Annotated Frame
0x1B in Microsoft.Maui.Controls.VisualElement.OnParentResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\VisualElement\VisualElement.cs:1446,5 C# Annotated Frame
0x16 in Microsoft.Maui.Controls.Element.OnParentResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\Element\Element.cs:618,5 C# Annotated Frame
0x28 in Microsoft.Maui.Controls.Element.OnResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\Element\Element.cs:649,6 C# Annotated Frame
0x10D in Microsoft.Maui.Controls.VisualElement.OnParentResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\VisualElement\VisualElement.cs:1466,5 C# Annotated Frame
0x16 in Microsoft.Maui.Controls.Element.OnParentResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\Element\Element.cs:618,5 C# Annotated Frame
0x28 in Microsoft.Maui.Controls.Element.OnResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\Element\Element.cs:649,6 C# Annotated Frame
0x2 in Microsoft.Maui.Controls.Element.OnParentResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\Element\Element.cs:623,4 C# Annotated Frame
0x1B in Microsoft.Maui.Controls.VisualElement.OnParentResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\VisualElement\VisualElement.cs:1446,5 C# Annotated Frame
0x16 in Microsoft.Maui.Controls.Element.OnParentResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\Element\Element.cs:618,5 C# Annotated Frame
0x28 in Microsoft.Maui.Controls.Element.OnResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\Element\Element.cs:649,6 C# Annotated Frame
0x2 in Microsoft.Maui.Controls.Element.OnParentResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\Element\Element.cs:623,4 C# Annotated Frame
0x1B in Microsoft.Maui.Controls.VisualElement.OnParentResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\VisualElement\VisualElement.cs:1446,5 C# Annotated Frame
0x16 in Microsoft.Maui.Controls.Element.OnParentResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\Element\Element.cs:618,5 C# Annotated Frame
0x28 in Microsoft.Maui.Controls.Element.OnResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\Element\Element.cs:649,6 C# Annotated Frame
0x2 in Microsoft.Maui.Controls.Element.OnParentResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\Element\Element.cs:623,4 C# Annotated Frame
0x16 in Microsoft.Maui.Controls.Element.OnParentResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\Element\Element.cs:618,5 C# Annotated Frame
0x28 in Microsoft.Maui.Controls.Element.OnResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\Element\Element.cs:649,6 C# Annotated Frame
0x2 in Microsoft.Maui.Controls.Element.OnParentResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\Element\Element.cs:623,4 C# Annotated Frame
0x17 in Microsoft.Maui.Controls.Application.OnParentResourcesChanged at D:\a_work\1\s\src\Controls\src\Core\Application\Application.cs:336,5 C# Annotated Frame
0x4B in Microsoft.Maui.Controls.Application.TriggerThemeChangedActual at D:\a_work\1\s\src\Controls\src\Core\Application\Application.cs:255,5 C# Annotated Frame
0x12 in Microsoft.Maui.Controls.Application.set_PlatformAppTheme at D:\a_work\1\s\src\Controls\src\Core\Application\Application.cs:190,5 C# Annotated Frame
0x6 in Microsoft.Maui.Controls.Application.Microsoft.Maui.IApplication.ThemeChanged at D:\a_work\1\s\src\Controls\src\Core\Application\Application.cs:503,4 C# Annotated Frame
0x21 in Microsoft.Maui.LifecycleEvents.AppHostBuilderExtensions.<>c.b__3_0 at D:\a_work\1\s\src\Core\src\Hosting\LifecycleEvents\AppHostBuilderExtensions.Android.cs:77,7 C# Annotated Frame
0xD in Microsoft.Maui.MauiAppCompatActivity. at D:\a_work\1\s\src\Core\src\Platform\Android\MauiAppCompatActivity.Lifecycle.cs:47,114 C# Annotated Frame
0x1F in Microsoft.Maui.LifecycleEvents.LifecycleEventServiceExtensions.InvokeLifecycleEvents<Microsoft.Maui.LifecycleEvents.AndroidLifecycle.OnConfigurationChanged> at D:\a_work\1\s\src\Core\src\LifecycleEvents\LifecycleEventServiceExtensions.cs:31,5 C# Annotated Frame
0x40 in Microsoft.Maui.MauiAppCompatActivity.OnConfigurationChanged at D:\a_work\1\s\src\Core\src\Platform\Android\MauiAppCompatActivity.Lifecycle.cs:47,4 C# Annotated Frame
0x11 in Android.App.Activity.n_OnConfigurationChanged_Landroid_content_res_Configuration at /Users/runner/work/1/s/xamarin-android/src/Mono.Android/obj/Release/net8.0/android-34/mcw/Android.App.Activity.cs:2926,4 C# Annotated Frame
0x9 in Android.Runtime.JNINativeWrapper.Wrap_JniMarshal_PPL_V at /Users/runner/work/1/s/xamarin-android/src/Mono.Android/Android.Runtime/JNINativeWrapper.g.cs:125,5 C# Annotated Frame

Which collection was modified? Downgrading nightly and my app works again.

[AlleSchonWeg]

Well, that no longer works. Theme propagation is now done through Parenting.

Hi @StephaneDelcroix
what ist Parenting? Is there a documentation how this works?
Thank you