NdefMessagepublic final class NdefMessage extends Object implements android.os.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 {@link #NdefMessage(byte[])} to construct an NDEF Message from
binary data, or {@link #NdefMessage(NdefRecord[])} to
construct from one or more {@link NdefRecord}s.
{@link NdefMessage} and {@link NdefRecord} implementations are
always available, even on Android devices that do not have NFC hardware.
{@link 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. |
| Fields Summary |
|---|
| private final NdefRecord[] | mRecords | | public static final Parcelable.Creator | CREATOR |
| Constructors Summary |
|---|
public NdefMessage(byte[] data)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 {@link 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 {@link NdefRecord#NdefRecord(short, byte[], byte[], byte[])}
If either strict validation of the binary format fails, or
basic validation during record construction fails, a
{@link 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
{@link NdefRecord#NdefRecord(short, byte[], byte[], byte[])},
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.
if (data == null) throw new NullPointerException("data is null");
ByteBuffer buffer = ByteBuffer.wrap(data);
mRecords = NdefRecord.parse(buffer, false);
if (buffer.remaining() > 0) {
throw new FormatException("trailing data");
}
| public NdefMessage(NdefRecord record, NdefRecord records)Construct an NDEF Message from one or more NDEF Records.
// validate
if (record == null) throw new NullPointerException("record cannot be null");
for (NdefRecord r : records) {
if (r == null) {
throw new NullPointerException("record cannot be null");
}
}
mRecords = new NdefRecord[1 + records.length];
mRecords[0] = record;
System.arraycopy(records, 0, mRecords, 1, records.length);
| public NdefMessage(NdefRecord[] records)Construct an NDEF Message from one or more NDEF Records.
// validate
if (records.length < 1) {
throw new IllegalArgumentException("must have at least one record");
}
for (NdefRecord r : records) {
if (r == null) {
throw new NullPointerException("records cannot contain null");
}
}
mRecords = records;
|
| Methods Summary |
|---|
| public int | describeContents()
return 0;
| | public boolean | equals(java.lang.Object obj)Returns true if the specified NDEF Message contains
identical NDEF Records.
if (this == obj) return true;
if (obj == null) return false;
if (getClass() != obj.getClass()) return false;
NdefMessage other = (NdefMessage) obj;
return Arrays.equals(mRecords, other.mRecords);
| | public int | getByteArrayLength()Return the length of this NDEF Message if it is written to a byte array
with {@link #toByteArray}.
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
{@link #toByteArray}.
int length = 0;
for (NdefRecord r : mRecords) {
length += r.getByteLength();
}
return length;
| | public NdefRecord[] | getRecords()Get the NDEF Records inside this NDEF Message.
An {@link 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 mRecords;
| | public int | hashCode()
return Arrays.hashCode(mRecords);
| | public byte[] | toByteArray()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.
int length = getByteArrayLength();
ByteBuffer buffer = ByteBuffer.allocate(length);
for (int i=0; i<mRecords.length; i++) {
boolean mb = (i == 0); // first record
boolean me = (i == mRecords.length - 1); // last record
mRecords[i].writeToByteBuffer(buffer, mb, me);
}
return buffer.array();
| | public java.lang.String | toString()
return "NdefMessage " + Arrays.toString(mRecords);
| | public void | writeToParcel(android.os.Parcel dest, int flags)
dest.writeInt(mRecords.length);
dest.writeTypedArray(mRecords, flags);
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