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TWebNFC

Keep in mind

This component is currently only supported on Android. For compatiblity please visit the MDN docs.

TWebNFC is a non-visual component to enable usage of NFC (Near Field Communication) from your browser. More specifically, you can read data via NFC as well as write data through NFC. The data must be in the NDEF record format. For more information you can refer to the Web NFC draft.

Supported tag types

  • NFC Forum Type 1 (ISO/IEC 14443-3A (NFC-A))
  • NFC Forum Type 2 (ISO/IEC 14443-3A (NFC-A))
  • NFC Forum Type 3 (ISO/IEC 18092)
  • NFC Forum Type 4 (ISO/IEC 14443-4 A/B (NFC A, NFC B))
  • NFC Forum Type 5 (ISO/IEC 15693 (NFC-V))
  • MIFARE Standard (ISO/IEC 14443-3A (NFC-A))

To see the full type specification please consult the Web NFC draft.

Read data

To read data, start by calling the Scan method. After accepting the permission prompt, your page will scan for any NFC tags that are hold close to your NFC reader device. If an NFC tag is detected and read, it will trigger the OnReading event. This event has an TJSNDEFMessageRecord parameter, where TJSNDEFMessageRecord.jsmessage gives you direct access to the underlying JavaScript object that contains the messages records.

For example, to read a text NDEF record, you can do the following: 

procedure TForm1.DoHandleNFCReading(Sender: TObject; ASerialNumber: string;
  AData: TJSNDEFMessageRecord);
var
  s: string;
  td: TJSTextDecoder;
begin
  if (Length(AData.jsmessage.records) > 0) and (AData.jsmessage.records[0].recordType = 'text') then
  begin
    td := TJSTextDecoder.new;
    WebMemo1.Text := td.decode(AData.jsmessage.records[0].data);
  end
  else
  begin
    ShowMessage('No text record found');
  end;
end;

Write data

We support 3 basic types of records out of the box: empty, text and uri. You can use WriteEmpty to write an empty record, WriteString(AData: string) to write a text record and WriteURL(AURL: string) to write a URI record onto your tag.

You can also write other, custom record types by using WriteCustom. Specify the record type as a string, the data as a string or binary and finally optionally you can also define the ID and mime-type of the data. For more information please consult the appropriate part of the Web NFC draft.

TForm2 = class(TWebForm)
  //...
  [async] procedure WebButton1Click(Sender: TObject);
  //...
end;

implementation

procedure TForm1.WebButton1Click(Sender: TObject);
var
  j: TJSONObject;
begin
  try
    TAwait.ExecP<JSValue>(nfc.WriteString('my data'))._then(function (aValue: JSValue): JSValue
    begin
      ShowMessage('Message successfully written!');
    end).catch(function (aValue: JSValue): JSValue
    begin
      ShowMessage('Message could not be written');
    end));
  finally
    j.Free;
  end;
end;

Doing any writing without a Scan call first might result in an immediate scan of the tag via the default NFC reader on your device. If you want to avoid that, you can always call Scan first, so that the reading that happens after writing is trapped by your application.

Stop the scanning

Simply call the Stop method to stop the scanning.

Methods for TWebNFC

Method Description
Scan Starts the scanning.
Stop Stops the scanning.
WriteCustom(ARecordType: string; AData: string; AID: string = ''; AMediaType: string = ''): TJSPromise Write a custom NDEF record to a tag.
WriteCustom(ARecordType: string; AData: TJSUint8Array = nil; AID: string = ''; AMediaType: string = ''): TJSPromise Write a custom NDEF record to a tag.
WriteEmpty: TJSPromise Write an empty NDEF record to a tag.
WriteString(AData: string): TJSPromise Write a text NDEF record to a tag.
WriteURL(AURL: string): TJSPromise Write a URI NDEF record to a tag.

Events for TWebNFC

Event Description
OnReading Event triggered when a tag is read.
OnReadingError Event triggered when a tag could not be read (e.g. unsupported type)