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| java.lang.Object | |
| ↳ | android.nfc.tech.Ndef |
Provides access to NDEF content and operations on a Tag.
Acquire a Ndef object using get(Tag).
NDEF is an NFC Forum data format. The data formats are implemented in
NdefMessage and
NdefRecord. This class provides methods to
retrieve and modify the NdefMessage
on a tag.
There are currently four NFC Forum standardized tag types that can be formatted to contain NDEF data.
NFC_FORUM_TYPE_1), such as the Innovision Topaz
NFC_FORUM_TYPE_2), such as the NXP MIFARE Ultralight
NFC_FORUM_TYPE_3), such as Sony Felica
NFC_FORUM_TYPE_4), such as NXP MIFARE Desfire
Ndef on NFC Forum Tag Types 1-4, and implement all NDEF operations
as defined in this class.
Some vendors have there own well defined specifications for storing NDEF data
on tags that do not fall into the above categories. Android devices with NFC
should enumerate and implement Ndef under these vendor specifications
where possible, but it is not mandatory. getType() returns a String
describing this specification, for example MIFARE_CLASSIC is
com.nxp.ndef.mifareclassic.
Android devices that support MIFARE Classic must also correctly
implement Ndef on MIFARE Classic tags formatted to NDEF.
For guaranteed compatibility across all Android devices with NFC, it is recommended to use NFC Forum Types 1-4 in new deployments of NFC tags with NDEF payload. Vendor NDEF formats will not work on all Android devices.
Note: Methods that perform I/O operations
require the NFC permission.
| Constants | |||||||||||
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| String | MIFARE_CLASSIC | NDEF on MIFARE Classic | |||||||||
| String | NFC_FORUM_TYPE_1 | NFC Forum Tag Type 1 | |||||||||
| String | NFC_FORUM_TYPE_2 | NFC Forum Tag Type 2 | |||||||||
| String | NFC_FORUM_TYPE_3 | NFC Forum Tag Type 4 | |||||||||
| String | NFC_FORUM_TYPE_4 | NFC Forum Tag Type 4 | |||||||||
| Public Methods | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Indicates whether a tag can be made read-only with
makeReadOnly().
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Disable I/O operations to the tag from this
TagTechnology object, and release resources.
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Enable I/O operations to the tag from this
TagTechnology object.
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Get an instance of
Ndef for the given tag.
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Get the
NdefMessage that was read from the tag at discovery time.
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Get the maximum NDEF message size in bytes.
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Read the current
NdefMessage on this tag.
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Get the
Tag object backing this TagTechnology object.
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Get the NDEF tag type.
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Helper to indicate if I/O operations should be possible.
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Determine if the tag is writable.
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Make a tag read-only.
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Overwrite the
NdefMessage on this tag.
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Inherited Methods | |||||||||||
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From class
java.lang.Object
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From interface
android.nfc.tech.TagTechnology
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From interface
java.io.Closeable
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From interface
java.lang.AutoCloseable
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NDEF on MIFARE Classic
NFC Forum Tag Type 1
NFC Forum Tag Type 2
NFC Forum Tag Type 4
NFC Forum Tag Type 4
Indicates whether a tag can be made read-only with makeReadOnly().
Does not cause any RF activity and does not block.
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.
| IOException |
|---|
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.
| IOException |
|---|
Get an instance of Ndef for the given tag.
Returns null if Ndef was not enumerated in getTechList().
This indicates the tag is not NDEF formatted, or that this tag
is NDEF formatted but under a vendor specification that this Android
device does not implement.
Does not cause any RF activity and does not block.
| tag | an NDEF compatible tag |
|---|
Get the NdefMessage that was read from the tag at discovery time.
If the NDEF Message is modified by an I/O operation then it will not be updated here, this function only returns what was discovered when the tag entered the field.
Note that this method may return null if the tag was in the INITIALIZED state as defined by NFC Forum, as in this state the tag is formatted to support NDEF but does not contain a message yet.
Does not cause any RF activity and does not block.
Get the maximum NDEF message size in bytes.
Does not cause any RF activity and does not block.
Read the current NdefMessage on this tag.
This always reads the current NDEF Message stored on the tag.
Note that this method may return null if the tag was in the INITIALIZED state as defined by NFC Forum, as in that state the tag is formatted to support NDEF but does not contain a message yet.
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.
| TagLostException | if the tag leaves the field |
|---|---|
| IOException | if there is an I/O failure, or the operation is canceled |
| FormatException | if the NDEF Message on the tag is malformed |
Get the Tag object backing this TagTechnology object.
Tag backing this TagTechnology object.
Get the NDEF tag type.
Returns one of NFC_FORUM_TYPE_1, NFC_FORUM_TYPE_2,
NFC_FORUM_TYPE_3, NFC_FORUM_TYPE_4,
MIFARE_CLASSIC or another NDEF tag type that has not yet been
formalized in this Android API.
Does not cause any RF activity and does not block.
Determine if the tag is writable.
NFC Forum tags can be in read-only or read-write states.
Does not cause any RF activity and does not block.
Requires NFC permission.
Make a tag read-only.
This sets the CC field to indicate the tag is read-only, and where possible permanently sets the lock bits to prevent any further modification of the memory.
This is a one-way process and cannot be reverted!
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.
| TagLostException | if the tag leaves the field |
|---|---|
| IOException | if there is an I/O failure, or the operation is canceled |
Overwrite the NdefMessage on this tag.
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.
| msg | the NDEF Message to write, must not be null |
|---|
| TagLostException | if the tag leaves the field |
|---|---|
| IOException | if there is an I/O failure, or the operation is canceled |
| FormatException | if the NDEF Message to write is malformed |