AN4430 datasheet(18/42 Pages) STMICROELECTRONICS

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How to create an Android Application for ST dual memories

AN4430

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DocID025722 Rev 1

NfcAdapter’s callback in order to keep backward compatibility as fields and parameter

may be added in the next API releases.

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Tag

This class implements the Tag that has been discovered (when a Tag is presented to

the android phone’s NFC field). This object is immutable as it represents the state of

the Tag at the time it has been discovered. This object is used to retrieve the tag ID

(getID() call) and the properties of the Tag like the supported technologies (getTecList()

call).

A new tag object is created every time a tag is discovered even if it is the same physical tag.

Developer must then ensure to always use the latest tag discovered to perform specific

action like TagTechnology interface manipulation.

When a tag is discovered, android system creates a tag object, store it in an intent message

and requests for a startActivity with the created intent in parameter.

Depending on the tag characteristics and on the installed applications a four stage dispatch

solution is used to select the most appropriate activity to handle the current detected tag

(see Figure 6 Tag Dispatch Startegy). Android system executes each stage in order and

complete dispatch as soon as a single matching activity is found.

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Stage 1 – Foreground Activity dispatch: a foreground activity which has called

NfcAdapter.enableForegroundDispatch(…) is given the priority. This call is generally

done in the onResume() activity state callback. To release this priority developer has to

call NfcAdapter.disableForegroundDispatch(Activity) generally in Pause() activity state

callback.

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Stage 2 – NDEF data dispatch: If the discovered tag contains at least an NDEF

message with a first Record with URI, SmartPoster or MimeData type Android system

call a startActivity() with ACTION_NDEF_DISCOVERED intent. Android System will

then look for a component ACTION_NDEF_DISCOVERED handling capable. If most

that one component is find, Android System requests to user to select the

application/component to launch to treat the pending intent. If none component is

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Stage 3 – Tag Technology dispatch: Android System call a startActivity() with

ACTION_TECH_DISCOVERED and look for a component capable to handle current

tagTechnology. If any component is register to handle at least one technology

supported by the tag Android System goes to Stage 4.

•

Stage 4 – Fall-back dispatch: Android System call a startActivity() with

ACTION_TAG_DISCOVERED and look for a component capable to handle current

intent.

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