CaveBirdLabs Blog

By Stefan de Vogelaere

In the last few days I've been struggling with the Xamarin.IOS Build Host. This little program is necessary if you want to use Microsoft Visual Studio and Xamarin's Monotouch.

My Parallels Windows 8.1 installation was unable to communicate with my MacBook Pro running Xamarin Studio with the Xamarin.IOS Build Host app. Because of that - although I only found out that later - Visual Studio 2013 was going nuts! Whenever I opened a solution that contained an IOS project Visual Studio became extremely unstable. I couldn't open a new solution once I loaded one with an IOS project; Visual Studio removed all my projects from the solution leaving only the solution open. I once didn't noticed it and when I tried to close Visual Studio I saved my solution losing my projects. Closing wasn't even possible - I had to use the Task Manager to forcefully close my Visual Studio instance.

The weird thing was that I actually thought it was a Parallels - Windows - Visual Studio thing. I had a perfect combination running at my office, so I copied the Virtual Machine to my Macbook Pro. When I started my VM I was pretty sure all things would work as expected - NOT! So it had to do with my OS X environment.

I tried the Xamarin Forums and Guides to get more info on how to troubleshoot the Xamarin.IOS Build Host:

http://developer.xamarin.com/guides/ios/getting_started/installation/windows/troubleshooting/offline.pdf

http://forums.xamarin.com/discussion/comment/6791/#Comment_6791

What I found out by reading these posts was that the Build Host was not running on port 5000. The HELO command did not return anything.

So I contacted Xamarin Support, and after a few mails Brendan Zagaeski asked me to run some test on OS X Terminal:

By running these test I found out that the port 5000 that the Xamarin.IOS Build Host uses was already occupied by Airserver! I stopped the Airserver app and the Build Host was able to run and connect to my VM! Eureka! In the follow up mail I received a link towards a "known" bug: https://bugzilla.xamarin.com/show_bug.cgi?id=20272

I like Airserver so I wanted to find out a way to change the port it was using. The article http://support.airserver.com/customer/portal/articles/1465944 gave me an insight in the ports that Airserver was using and the names of the settings that could be changed. 

I fired up Terminal and changed the Airplay Audio Port into 5010:

By Stefan de Vogelaere

I really like what Xamarin did with the release of Xamarin 3.0 especially the introduction of Xamarin.Forms. With this cross platform UI technology you can build native user interfaces for IOS, Android and the Windows Phone platforms. What's even nicer about this, is the fact that you can extend it yourself!

Extending the library can be done by using renderers for each platform. You can inherit from existing renderers or you can create completely new ones. More information can be found in the documentation of Xamarin.Forms.

As explained in the documentation a renderer is placed inside the platform specific app code. When you want to re-use that code in another app you'll need to share that code or better, move the renderer code inside a separate assembly. 

However, this isn't currently working as expected. When you move the renderer into a separate assembly and you reference this assembly from your app, the custom renderer is not used.

When I contacted the Xamarin support staff about it, I got following reply:

After consulting with the Xamarin Forms team, this is a known issue but not a bug or even an issue with Xamarin Forms per se. The library was not getting linked in or loaded to your project because even though it is referenced, no code from it was called so the assembly was skipped. The engineering team is discussing it to see if there is a way around this issue, but for now this is expected behavior and you will need to continue using that hack.

The hack that I was using is simple and easy. In my platform specific renderer assembly I placed following code:

In the AppDelegate.cs app of my IOS implementation I call the empty method:

That way the renderer assembly is loading and Xamarin.Forms can use it.

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