UIApplication: AccessibilityLanguage API appears to be missing

[Felix-Dev]

Apple platform

iOS

Framework version

net8.0-*

Affected platform version

.NET 8.0.303

Description

We are currently working on adding accessibility to our app and support for Apple VoiceOver. The display language of our app might differ from the user's system language. For example, the user might have configured their iPhone to display system UI in English, however, our app UI content in German. We've noticed that in this case VoiceOver pronounces our German labels as if they represent English words which is expected behavior:

If you don't set a language, the system uses the user’s current language setting.

(https://developer.apple.com/documentation/objectivec/nsobject/1615192-accessibilitylanguage?language=objc#discussion)

It is possible to configure the language used when speaking the label/accessibility description/etc... using the API

accessibilityLanguage

(https://developer.apple.com/documentation/objectivec/nsobject/1615192-accessibilitylanguage?language=objc)
While this property can bet set on every UIView it looks like it is also possible to set it globally using the UIApplication instance:

application.accessibilityLanguage = @"de";

(https://stackoverflow.com/questions/21283862/uiaccessibility-default-language-throughout-the-app)

I have tried to do the same in a MAUI app but I did not find such a property:

It looks like the API is missing from the Xamari iOS bindings? One thing I noticed is that for .NET for iOS, the AccessibilityLanguage API is defined first for an UIView:
https://learn.microsoft.com/en-us/dotnet/api/uikit.uiview.accessibilitylanguage?view=xamarin-ios-sdk-12
Whereas in UIKit, that API is defined for a NSObject. UIApplication is a NSObject but not a UIView which technically explains why that property is missing here.

Steps to Reproduce

n/a

Did you find any workaround?

No feasible workaround yet.

Relevant log output

No response

[rolfbjarne]

Looks like our UIApplication bindings are missing conformance to the UIAccessibility protocol.

I'll have a look.

As a workaround, something like this should work:

using System.Runtime.InteropServices;
using CoreFoundation;
using Foundation;
using ObjCRuntime;

public static class UIAppearanceExtensions {
	public static void SetAccessibilityLanguage (this NSObject object, string language)
	{
		var languageHandle = CFString.CreateNative (language);
		objc_msgSend (object.GetHandle (), Selector.GetHandle ("setAccessibilityLanguage:"), languageHandle);
		CFString.ReleaseNative (languageHandle);
	}

	[DllImport (Constants.ObjectiveCLibrary)]
	static extern void objc_msgSend (IntPtr handle, IntPtr selector, IntPtr arg0);
}

and then you can use it like this:

application.SetAccessibilityLanguage ("de");

[Felix-Dev]

@rolfbjarne Thanks for the quick workaround (I can confirm it works) and fix!