Well, it's not as hard as it might seem. Basically, Java and C# are extremely similar and code can easily be converted from one to the other. It was harder for me to switch from .NET framework for Win7 to .NET framework for Windows metro apps, then to transfer to Java/Android. I was never good in front end, but it seems to me that differences are not that big in this field either.
At the end, I would like to point out that I once tried to create a "Hello world" app from iPhone, just to find out how remarkably similar Java and C# actually are compering to objective C.