Tuesday, January 15, 2013

How to: Receive NFC data in an Adobe AIR Android app

Getting NFC data into an Adobe AIR for Android application is much easier than it might seem. At least, it's a lot easier than I thought it would be.

I'm currently working on an app that has just such a need. Specifically, users will run the AIR app and then swipe their device over a physical display that has some NFC tag hotspots. The app needs to receive the NFC data from each tag and react in a specific fashion. I didn't know much about NFC data when I began working on this current app, and since AIR doesn't have official support for NFC I figured I would need a native extension to properly handle things.

It turns out it is *much* simpler than needing to implement any sort of native functionality. All you have to do is add the proper intent handling to the "manifestAdditions" portion of the AIR application xml. I'll put a sample xml block here, and then explain it:

The key to making everything work is in effect "extending" the <application> node - which prior to discovering this I didn't know was possible. By adding the appropriate NFC intent filter information - the "default" way you handle NFC data in Android - the AIR application is handed the day the same way any other Android application would be.

In the xml sample above, I have  my AIR app responding to a URI. I've got placeholders for the scheme and host attribute values. Most commonly these will represent a web URL; in that case scheme would be "http" and host would be the domain - "". But if you want to use proprietary data, you can do that too. Scheme and host can be anything. Scheme could be "my" and host could be "uri.value" which would represent "my://uri.value." It doesn't really matter, the data will make it to the AIR app. This is just one way of targeting NFC data into an app - there are a number of different ways to use intent filters in Android to target varied NFC data types. Virtually all of them should work as manifest extensions for an AIR app. The Android documentation has information about targeting NFC data here.

Extending the manifest only gets us so far; it doesn't tell us how the data gets into the AIR application. Thankfully, Adobe has facilitated that too. Anytime the app responds to intent filter data, an InvokeEvent.INVOKE event gets fired. Check out the below class:

To be clear, the invoke event will in fact be fired when the app starts up, but will *also* be fired whenever the NFC intent data qualifies and is passed to the app. This means that the app will be handed any and all relevant NFC data and can respond by reading the events.arguments data.

This also has the added effect of launching your AIR application whenever the relevant NFC data is swiped. That's actually what Android generally means to have happen with NFC data - the user swipes their device and the relevant specific application is opened. This will in fact do that. But as this post discusses, it will also pass in the NFC data while the application is running.

If you aren't wanting the app to be launched on NFC data but instead *only* respond to the NFC data while the application is open, that requires more complexity. It does, in fact require a native extension interacting with something called the "Foreground Dispatch". A very intelligent person has actually cracked the code and has made, well, the source code available for free! You can see it here:

I hope this helps!