public
final
class
NfcA
extends Object
implements
TagTechnology
| java.lang.Object | |
| ↳ | android.nfc.tech.NfcA |
Provides access to NFC-A (ISO 14443-3A) properties and I/O operations on a Tag.
Acquire a NfcA object using get(Tag).
The primary NFC-A I/O operation is transceive(byte[]). Applications must
implement their own protocol stack on top of transceive(byte[]).
Note: Methods that perform I/O operations
require the NFC permission.
Public methods | |
|---|---|
void
|
close()
Disable I/O operations to the tag from this |
void
|
connect()
Enable I/O operations to the tag from this |
static
NfcA
|
get(Tag tag)
Get an instance of |
byte[]
|
getAtqa()
Return the ATQA/SENS_RES bytes from tag discovery. |
int
|
getMaxTransceiveLength()
Return the maximum number of bytes that can be sent with |
short
|
getSak()
Return the SAK/SEL_RES bytes from tag discovery. |
Tag
|
getTag()
Get the |
int
|
getTimeout()
Get the current |
boolean
|
isConnected()
Helper to indicate if I/O operations should be possible. |
void
|
setTimeout(int timeout)
Set the |
byte[]
|
transceive(byte[] data)
Send raw NFC-A commands to the tag and receive the response. |
Inherited methods | |
|---|---|
 From
class
java.lang.Object
| |
From
interface
android.nfc.tech.TagTechnology
| |
From
interface
java.io.Closeable
| |
From
interface
java.lang.AutoCloseable
| |
void close ()
Disable I/O operations to the tag from this TagTechnology object, and release resources.
Also causes all blocked I/O operations on other thread to be canceled and
return with IOException.
Requires the NFC permission.
| Throws | |
|---|---|
IOException |
|
void connect ()
Enable I/O operations to the tag from this TagTechnology object.
May cause RF activity and may block. Must not be called
from the main application thread. A blocked call will be canceled with
IOException by calling close() from another thread.
Only one TagTechnology object can be connected to a Tag at a time.
Applications must call close() when I/O operations are complete.
Requires the NFC permission.
| Throws | |
|---|---|
IOException |
|
NfcA get (Tag tag)
Get an instance of NfcA for the given tag.
Returns null if NfcA was not enumerated in getTechList().
This indicates the tag does not support NFC-A.
Does not cause any RF activity and does not block.
| Parameters | |
|---|---|
tag |
Tag:
an NFC-A compatible tag |
| Returns | |
|---|---|
NfcA |
NFC-A object |
byte[] getAtqa ()
Return the ATQA/SENS_RES bytes from tag discovery.
Does not cause any RF activity and does not block.
| Returns | |
|---|---|
byte[] |
ATQA/SENS_RES bytes |
int getMaxTransceiveLength ()
Return the maximum number of bytes that can be sent with transceive(byte[]).
| Returns | |
|---|---|
int |
the maximum number of bytes that can be sent with transceive(byte[]).
|
short getSak ()
Return the SAK/SEL_RES bytes from tag discovery.
Does not cause any RF activity and does not block.
| Returns | |
|---|---|
short |
SAK bytes |
Tag getTag ()
Get the Tag object backing this TagTechnology object.
| Returns | |
|---|---|
Tag |
the Tag backing this TagTechnology object.
|
int getTimeout ()
Get the current transceive(byte[]) timeout in milliseconds.
Requires the NFC permission.
| Returns | |
|---|---|
int |
timeout value in milliseconds |
boolean isConnected ()
Helper to indicate if I/O operations should be possible.
Returns true if connect() has completed, and close() has not been
called, and the Tag is not known to be out of range.
Does not cause RF activity, and does not block.
| Returns | |
|---|---|
boolean |
true if I/O operations should be possible |
void setTimeout (int timeout)
Set the transceive(byte[]) timeout in milliseconds.
The timeout only applies to transceive(byte[]) on this object,
and is reset to a default value when close() is called.
Setting a longer timeout may be useful when performing transactions that require a long processing time on the tag such as key generation.
Requires the NFC permission.
| Parameters | |
|---|---|
timeout |
int:
timeout value in milliseconds
|
byte[] transceive (byte[] data)
Send raw NFC-A commands to the tag and receive the response.
Applications must not append the EoD (CRC) to the payload, it will be automatically calculated.
Applications must only send commands that are complete bytes, for example a SENS_REQ is not possible (these are used to manage tag polling and initialization).
Use getMaxTransceiveLength() to retrieve the maximum number of bytes
that can be sent with transceive(byte[]).
This is an I/O operation and will block until complete. It must
not be called from the main application thread. A blocked call will be canceled with
IOException if close() is called from another thread.
Requires the NFC permission.
| Parameters | |
|---|---|
data |
byte:
bytes to send |
| Returns | |
|---|---|
byte[] |
bytes received in response |
| Throws | |
|---|---|
|
if the tag leaves the field |
IOException |
if there is an I/O failure, or this operation is canceled |
Developers