Adobe Air explanation

Question

The quick answer is yes, the long answer is no.

You can create one code base and have it run on Mac, Windows, iOS, and Android. It is unlikely, however, that you will be able to do so and I will actively recommend against doing it.

If you use Flex, then you likely will not be able to do this. Flex Mobile relies on the ViewNavigator base class, generally, which is not available for desktop. So a mobile app would most likely not be translatable to Desktop easily (i.e. it would probably require a complete rewrite). You don't want to not use ViewNavigator on mobile, either, since it is highly optimized for mobile performance.

For a standard AS3 project, it would be possible. The issue comes with mobile optimization and mobile design patterns. If you look at a mobile app and compare it to a desktop app (say something like Evernote which is cross-platform), their design is completely different. You interact with a mobile app completely differently than you do with a desktop app and, in general, it does not translate well. Additionally, scrolling is difficult to get right unless you are using Flex and you would have to have 2-3 separate (Desktop, iOS, and Android all have different scroll behaviors) algorithms for it.

I recommend using AS3. HTML/JS really has not been supported for quite some time (I want to say it stopped with 3.0, though I could be wrong), as far as I am aware. If you want to build a mobile app, you must use the latest version of AIR (4.x, last release two weeks ago) because you will not be able to publish to the iTunes Store otherwise (now requires XCode 5, among other iOS 7-specific updates). Additionally, make sure you are using the most recent version of Flex (4.12), if you use that SDK. The latest versions, since Apache acquired the project, has put mobile optimization at the forefront and performance compared to Adobe's last version (4.6) is like night and day.