Ndef Record Creation in NFC Data exchange Format

Question

we want to write the following data into NFC:(In two separate lines)

Id:A112
Result:Pass

and got stuck with NdefRecord creation of MIME type text/plain. Actually found two ways of doing so:

• one with constuctor

  public NdefRecord (short tnf, byte[] type, byte[] id, byte[] payload)
  

• other one by using the Static method

  public static NdefRecord createMime (String mimeType, byte[] mimeData) 
  

Using the static createMime method, we can create the record as:

byte[] stringBytes = "Id:A112Result:Pass".getBytes();
NdefRecord.createMime("text/plain", stringBytes);

How to achieve the same with constructor NdefRecord and what's the difference between the above two ways? Also how do we write the above data (Id:A112Result:Pass) into NFC in two lines into a single record.

Answer 1

The equivalent of

public static NdefRecord createMime (String mimeType, byte[] mimeData)

using the NdefRecordconstructor directly is something like this:

public NdefRecord myCreateMime (String mimeType, byte[] mimeData) {
    return new NdefRecord(
            NdefRecord.TNF_MIME_MEDIA,
            mimeType.getBytes("US-ASCII"),
            null,
            mimeData)
}

In general I would avoid using the text/plain MIME type. This MIME type does not give the payload data any meaning other than it is human-readable text. If you want to convey a specific meaning use an appropriate MIME type that reflects the contents of your payload data or better use a custom NFC Forum external type.

Also note that the MIME type text/plain uses US-ASCII character encoding by default. However, using "Id:A112Result:Pass".getBytes() will give you UTF-8 encoding on Android. So you should explicitly specify the character encoding when converting a string to bytes:

byte[] stringBytes = "Id:A112Result:Pass".getBytes("US-ASCII");

Last, if you want to insert a line break anywhere in a text, you would use the new-line escape character \n or a combination of carriage return + line feed \r\n (depending on your target system's needs).