It is a busy time for cross-platform toolkits. Adobe has released AIR 2.6, and reading the list of what’s new you would think it was mainly for mobile, since the notes focus on new features for Apple iOS, though AIR is also a runtime for Windows, Linux and desktop Mac. New features for iOS include GPU rendering – a form of hardware accelerated graphics – access to the camera, microphone, and camera roll, and embedded Webkit for apps that use web content. On Google Android, you can now debug on devices connected via USB.

There is also a new feature called “owned native windows” which lets you have a group of windows that remain together in the Z order – this lets you have things like floating toolbars without odd results where toolbars get hidden underneath other applications.

Asynchronous decoding of bitmaps is another new feature, allowing images to be processed in the background. This seems like a stopgap solution to overcome the lack of mullti-threading in AIR, but useful nonetheless.

Since the Flash runtime does not run on iOS, Adobe has a packager that compiles an AIR application into a native app. This is now called the AIR Developer Tool or ADT. You can use the ADT to target Windows, Linux or Android as well; however platforms other than iOS still need the AIR runtime installed.

Adobe is dropping support for the original iPhone and the iPhone 3G. iPhone 3GS or higher is needed.

If you want to build a cross-platform app but prefer .NET to Adobe’s Flash and ActionScript, the Mono folk have what you need. I’d guess that the Mono team has a small fraction of the resources of Adobe; but nevertheless it has delivered MonoTouch for iOS and is working on MonoDroid for Android. Just completed in its 1.0 version is MonoMac, for building Cocoa applications on Apple OSX. Mono is not fully cross-platform, since the GUI framework is different on the various platforms, but you do get to use C# throughout.

I am happy to agree that true native code is usually a better solution for any one platform; but at a time when the number of viable platforms is increasing the attraction of cross-platform has never been greater.