Android system NFC framework introduction and develop guide

operations are accessible. API level 10 includes comprehensive reader/writer support as well as foreground NDEF pushing, and API level 14 provides an easier way to push

NDEF messages to other devices with Android Beam and extra convenience methods to create NDEF records.

The uses-feature element so that your application shows up in the Android Market

only for devices that have NFC hardware:

If your application uses NFC functionality, but that functionality is not crucial to your application, you can omit the uses-feature element and check for NFC avalailbility at runtime by checking to see if getDefaultAdapter() is null. Filtering for NFC Intents

To start your application when an NFC tag that you want to handle is scanned, your application can filter for one, two, or all three of the NFC intents in the Android manifest. However, you usually want to filter for the ACTION_NDEF_DISCOVERED intent for the most control of when your application starts. The ACTION_TECH_DISCOVERED intent is a fallback for ACTION_NDEF_DISCOVERED when no applications filter for ACTION_NDEF_DISCOVERED or for when the payload is not NDEF. Filtering for ACTION_TAG_DISCOVERED is usually too general of a category to filter on. Many applications will filter for ACTION_NDEF_DISCOVERED or ACTION_TECH_DISCOVERED before ACTION_TAG_DISCOVERED, so your application has a low probability of starting. ACTION_TAG_DISCOVERED is only available as a last resort for

applications to filter for in the cases where no other applications are installed to handle the ACTION_NDEF_DISCOVERED or ACTION_TECH_DISCOVEREDintent.

Because NFC tag deployments vary and are many times not under your control, this is not always possible, which is why you can fallback to the other two intents when necessary. When you have control over the types of tags and data written, it is recommended that you use NDEF to format your tags. The following sections describe how to filter for each type of intent.

ACTION_NDEF_DISCOVERED