NdefMessage  |  API reference  |  Android Developers (original) (raw)

class NdefMessage : Parcelable

Represents an immutable NDEF Message.

NDEF (NFC Data Exchange Format) is a light-weight binary format, used to encapsulate typed data. It is specified by the NFC Forum, for transmission and storage with NFC, however it is transport agnostic.

NDEF defines messages and records. An NDEF Record contains typed data, such as MIME-type media, a URI, or a custom application payload. An NDEF Message is a container for one or more NDEF Records.

When an Android device receives an NDEF Message (for example by reading an NFC tag) it processes it through a dispatch mechanism to determine an activity to launch. The type of the first record in the message has special importance for message dispatch, so design this record carefully.

Use [NdefMessage(byte[])](#NdefMessage%28kotlin.ByteArray%29) to construct an NDEF Message from binary data, or [NdefMessage(android.nfc.NdefRecord[])](#NdefMessage%28kotlin.Array%29) to construct from one or more [NdefRecord](/reference/kotlin/android/nfc/NdefRecord)s.

[NdefMessage](#) and [NdefRecord](/reference/kotlin/android/nfc/NdefRecord) implementations are always available, even on Android devices that do not have NFC hardware.

[NdefRecord](/reference/kotlin/android/nfc/NdefRecord)s are intended to be immutable (and thread-safe), however they may contain mutable fields. So take care not to modify mutable fields passed into constructors, or modify mutable fields obtained by getter methods, unless such modification is explicitly marked as safe.

Summary

Inherited constants
From class Parcelable Int CONTENTS_FILE_DESCRIPTOR Descriptor bit used with describeContents(): indicates that the Parcelable object's flattened representation includes a file descriptor. Int PARCELABLE_WRITE_RETURN_VALUE Flag for use with writeToParcel: the object being written is a return value, that is the result of a function such as "Parcelable someFunction()", "void someFunction(out Parcelable)", or "void someFunction(inout Parcelable)". Some implementations may want to release resources at this point.
Public constructors
NdefMessage(record: NdefRecord!, vararg records: NdefRecord!) Construct an NDEF Message from one or more NDEF Records.
NdefMessage(records: Array<NdefRecord!>!) Construct an NDEF Message from one or more NDEF Records.
NdefMessage(data: ByteArray!) Construct an NDEF Message by parsing raw bytes.
Public methods
Int describeContents()
Boolean equals(other: Any?) Returns true if the specified NDEF Message contains identical NDEF Records.
Int getByteArrayLength() Return the length of this NDEF Message if it is written to a byte array with toByteArray.
Array<NdefRecord!>! getRecords() Get the NDEF Records inside this NDEF Message.
Int hashCode()
ByteArray! toByteArray() Return this NDEF Message as raw bytes.
String toString()
Unit writeToParcel(dest: Parcel, flags: Int)
Properties
static Parcelable.Creator<NdefMessage!> CREATOR

Public constructors

NdefMessage

NdefMessage(
    record: NdefRecord!,
    vararg records: NdefRecord!)

Construct an NDEF Message from one or more NDEF Records.

Parameters
record NdefRecord!: first record (mandatory)
records NdefRecord!: additional records (optional)

NdefMessage

NdefMessage(records: Array<NdefRecord!>!)

Construct an NDEF Message from one or more NDEF Records.

Parameters
records Array<NdefRecord!>!: one or more records

NdefMessage

NdefMessage(data: ByteArray!)

Construct an NDEF Message by parsing raw bytes.

Strict validation of the NDEF binary structure is performed: there must be at least one record, every record flag must be correct, and the total length of the message must match the length of the input data.

This parser can handle chunked records, and converts them into logical [NdefRecord](/reference/kotlin/android/nfc/NdefRecord)s within the message.

Once the input data has been parsed to one or more logical records, basic validation of the tnf, type, id, and payload fields of each record is performed, as per the documentation on on [NdefRecord.NdefRecord(short, byte[], byte[], byte[])](/reference/kotlin/android/nfc/NdefRecord#NdefRecord%28kotlin.Short,%20kotlin.ByteArray,%20kotlin.ByteArray,%20kotlin.ByteArray%29)

If either strict validation of the binary format fails, or basic validation during record construction fails, a [FormatException](/reference/kotlin/android/nfc/FormatException) is thrown

Deep inspection of the type, id and payload fields of each record is not performed, so it is possible to parse input that has a valid binary format and confirms to the basic validation requirements of [NdefRecord.NdefRecord(short, byte[], byte[], byte[])](/reference/kotlin/android/nfc/NdefRecord#NdefRecord%28kotlin.Short,%20kotlin.ByteArray,%20kotlin.ByteArray,%20kotlin.ByteArray%29), but fails more strict requirements as specified by the NFC Forum.

It is safe to re-use the data byte array after construction: this constructor will make an internal copy of all necessary fields.

Parameters
data ByteArray!: raw bytes to parse
Exceptions
android.nfc.FormatException if the data cannot be parsed

Public methods

equals

fun equals(other: Any?): Boolean

Returns true if the specified NDEF Message contains identical NDEF Records.

Parameters
obj This value may be null.
Return
Boolean true if this object is the same as the obj argument; false otherwise.

getByteArrayLength

fun getByteArrayLength(): Int

Return the length of this NDEF Message if it is written to a byte array with [toByteArray](#toByteArray%28%29).

An NDEF Message can be formatted to bytes in different ways depending on chunking, SR, and ID flags, so the length returned by this method may not be equal to the length of the original byte array used to construct this NDEF Message. However it will always be equal to the length of the byte array produced by [toByteArray](#toByteArray%28%29).

Return
Int length of this NDEF Message when written to bytes with toByteArray

getRecords

fun getRecords(): Array<NdefRecord!>!

Get the NDEF Records inside this NDEF Message.

An [NdefMessage](#) always has one or more NDEF Records: so the following code to retrieve the first record is always safe (no need to check for null or array length >= 1):

NdefRecord firstRecord = ndefMessage.getRecords()[0];

Return
Array<NdefRecord!>! array of one or more NDEF records.

hashCode

fun hashCode(): Int

Return
Int a hash code value for this object.

toByteArray

fun toByteArray(): ByteArray!

Return this NDEF Message as raw bytes.

The NDEF Message is formatted as per the NDEF 1.0 specification, and the byte array is suitable for network transmission or storage in an NFC Forum NDEF compatible tag.

This method will not chunk any records, and will always use the short record (SR) format and omit the identifier field when possible.

Return
ByteArray! NDEF Message in binary format

toString

fun toString(): String

Return
String a string representation of the object.

Properties