Android Development Manual
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TagTechnology
public interface TagTechnology
implements Closeable
| android.nfc.tech.TagTechnology |
 Known Indirect Subclasses
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TagTechnology is an interface to a technology in a Tag.
Obtain a TagTechnology implementation by calling the static method get() on the implementation class.
NFC tags are based on a number of independently developed technologies and offer a wide range of capabilities. The TagTechnology implementations provide access to these different technologies and capabilities. Some sub-classes map to technology specification (for example NfcA, IsoDep, others map to pseudo-technologies or capabilities (for example Ndef, NdefFormatable).
It is mandatory for all Android NFC devices to provide the following TagTechnology implementations.
NfcA(also known as ISO 14443-3A)NfcB(also known as ISO 14443-3B)NfcF(also known as JIS 6319-4)NfcV(also known as ISO 15693)IsoDepNdefon NFC Forum Type 1, Type 2, Type 3 or Type 4 compliant tags
TagTechnology implementations. If it is not provided, the Android device will never enumerate that class via
getTechList().
MifareClassicMifareUltralightNfcBarcodeNdefFormatablemust only be enumerated on tags for which this Android device is capable of formatting. Proprietary knowledge is often required to format a tag to make it NDEF compatible.
TagTechnology implementations provide methods that fall into two classes: cached getters and I/O operations.
Cached getters
These methods (usually prefixed byget or
is) return properties of the tag, as determined at discovery time. These methods will never block or cause RF activity, and do not require
connect() to have been called. They also never update, for example if a property is changed by an I/O operation with a tag then the cached getter will still return the result from tag discovery time.
I/O operations
I/O operations may require RF activity, and may block. They have the following semantics.connect()must be called before using any other I/O operation.close()must be called after completing I/O operations with aTagTechnology, and it will cancel all other blocked I/O operations on other threads (includingconnect()withIOException.- Only one
TagTechnologycan be connected at a time. Other calls toconnect()will returnIOException. - I/O operations may block, and should never be called on the main application thread.
Note: Methods that perform I/O operations require the NFC permission.
Summary
Public methods |
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|---|---|
abstract void |
close() Disable I/O operations to the tag from this |
abstract void |
connect() Enable I/O operations to the tag from this |
abstract Tag |
getTag() Get the |
abstract boolean |
isConnected() Helper to indicate if I/O operations should be possible. |
Inherited methods |
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|---|---|
From interface java.io.Closeable
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From interface java.lang.AutoCloseable
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Public methods
close
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 |
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See also:
connect
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 | |
|---|---|
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if the tag leaves the field |
IOException |
if there is an I/O failure, or connect is canceled |
See also:
getTag
Tag getTag ()
Get the Tag object backing this TagTechnology object.
| Returns | |
|---|---|
Tag |
the Tag backing this TagTechnology object. |
isConnected
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 |