As I’ve continued working on the Xamarin.Forms application I’ve been building, I’ve learned a lot. One of the issues I ran into was an error in the iOS version of my application and as I didn’t find an easy to understand solution, I thought I would document it here. I’ll list the error first then explain the scenario and how to fix it.

AX Exchange error: Error Domain=Accessibility Code=0 “Remote service does not respond to _accessibilityMachPort” UserInfo={NSLocalizedDescription=Remote service does not respond to _accessibilityMachPort}

Part of the application revolves around uploading files. For Android this isn’t very difficult and it even makes sense as Android has a file system you can access and external storage in the form of SD cards. With iOS you can store files for your own app but not others (for the most part). However, you can access a user’s iCloud if they grant you permission. To this end, I started looking at the FilePicker Plugin for Xamarin and Windows.

In theory what this plugin would do is with one call open up a file picker connected to iCloud on iOS and to the disk on Android (and who knows on Windows). This plugin works great for Android. However, for iOS calling the PickFile method results in this error:

This functionality is not implemented in the portable version of this assembly. You should reference the NuGet package from your main application project in order to reference the platform-specific implementation.

At the time of writing, it appears the author knows about the issue but hasn’t yet pushed a fix out to NuGet. So instead, I took that code and baked it into my app for Android and iOS and it worked for both. However, when the picker pops up to let you pick a file from iCloud, it comes along with the error being printed out to Application Output over and over and over again:

AX Exchange error: Error Domain=Accessibility Code=0 “Remote service does not respond to _accessibilityMachPort” UserInfo={NSLocalizedDescription=Remote service does not respond to _accessibilityMachPort}

I did a bit of searching and didn’t find anything DIRECTLY related to the FilePicker but I did find something about custom keyboards and external testing frameworks.
Xamarin.iOS apps are wired to use Calabash for testing with Xamarin Test Cloud and you will find this in the AppDelegate:

#if ENABLE_TEST_CLOUD
			Xamarin.Calabash.Start();
#endif

Commenting that out led to the error no longer occurring. I’m not 100% sure what the is causing this issue but at least there is a quick fix.


Chris Risner