ExEn (XNA -> iOS, Android) and accelerometers, etc

Question

I've been reading about Andrew Russell's ExEn project and I'm wondering what the flow would be like for creating a WP7 accelerometer-based game and then porting it to another platform, say iOS. Here's what I hope would happen:

1. Create fully functional game in XNA, avoiding dependance on device specific items like the 'back' button.
2. Run the project through ExEn (I have no idea on how this would happen), creating fully functional iOS game.
3. Run game on iPhone.

Sorry for that pitiful outline, but I just don't have a solid high-level view after reading about it.

Also, being software conversion, surely it wouldn't totally work. How would you iron out the wrinkles? I assume you'd have to know iOS or Android fairly well to pin it down.

Anyway, if anyone can move me one step closer I would appreciate it.

Answer 1

ExEn is an implementation of a subset of the XNA API that runs on different platforms (including iOS and Android). Put simply, it makes the classes and methods that you use when writing XNA code available to you on these other platforms. (Plus appropriate instructions, examples, etc.)

When using ExEn, the bulk of your code should simply "just work". However in most real-world cases you will need to write at least some platform-specific code (and probably provide some platform-specific assets). In particular to support different device resolutions, and also in cases where you use XNA features not available in ExEn.

At time of writing, ExEn does not implement the XNA/WP7 APIs for accelerometer support. At some time in the future they may be added (either by me or anyone who wants to contribute a patch). ExEn is distributed as source code, so you could even add the necessary support yourself.

The alternative would be to write platform-specific code for the parts of your game that query the accelerometer. Using ExEn does not prevent you from also using the APIs of the underlying platform.

ExEn (on iOS and Android) runs on top of Xamarin's MonoTouch and Mono for Android products. These two products provide C# bindings for the underlying platform APIs. Also, much like ExEn implements the XNA APIs, Mono implements the .NET APIs. These products also provide you with the tools you need (IDE, compiler, debugger, etc).

So the iOS API that you would use is UIAccelerometer (doc). This is exposed in C# via MonoTouch.UIKit.UIAccelerometer (doc). I'll leave looking up the Android equivalents as an exercise.

Answer 2

You can't expect:

• porting a game to other platform and don't modify it.
• porting a game with special platform inherent abilities to other platform that lacks this abilities, or vice versa