public async Task <NdefMessage> ReadNdefAsync()
{
try
{
await _lockSemaphore.WaitAsync();
if (!_isSessionEnabled)
{
throw new Exception("NFC is not enabled");
}
var tcs = new TaskCompletionSource <NdefMessage>();
_tag.ReadNdef((iosNdefMessage, error) =>
{
if (error != null)
{
throw new Exception(error.Description);
}
var ndefMessage = new NdefMessage();
ndefMessage.AddRange(iosNdefMessage.Records.Select(iosRecord => new NdefRecord
{
Id = iosRecord.Identifier.ToArray(),
Type = iosRecord.Type.ToArray(),
TypeNameFormat = (NdefRecord.TypeNameFormatType)iosRecord.TypeNameFormat,
Payload = iosRecord.Payload.ToArray()
}));
tcs.SetResult(ndefMessage);
});
return(await tcs.Task);
}
finally
{
_lockSemaphore.Release();
}
}
/// <summary>
/// Reverse function to parseRecords() - this one takes
/// the information stored in the individual record instances and assembles
/// it into the payload of the base class.
/// </summary>
/// <remarks>
/// As the URI is mandatory, the payload will not be assembled
/// if no URI is defined.
/// </remarks>
/// <returns>Whether assembling the payload was successful.</returns>
private bool AssemblePayload()
{
// Uri is mandatory - don't assemble the payload if it's not set
if (RecordUri == null) return false;
// URI (mandatory)
var message = new NdefMessage { RecordUri };
// Title(s) (optional)
if (Titles != null && Titles.Count > 0)
message.AddRange(Titles);
// Action (optional)
if (ActionInUse())
message.Add(_recordAction);
// Size (optional)
if (SizeInUse())
message.Add(_recordSize);
// Mime Type (optional)
if (MimeTypeInUse())
message.Add(_recordMimeType);
// Image (optional)
if (ImageInUse())
message.Add(_recordImage);
SetPayloadAndParse(message.ToByteArray(), false);
return true;
}
/// <summary>
/// Create the payload based on the data stored in the properties. Usually called
/// automatically when changing properties, but you might need to call this manually
/// if you modify the list of alternative carrier records directly without using
/// accessor method provided by this class.
/// </summary>
/// <exception cref="NdefException">Thrown if unable to assemble the payload.
/// The exception message contains further details about the issue.</exception>
public void AssemblePayload()
{
if (_handoverVersion == null)
{
throw new NdefException(NdefExceptionMessages.ExHandoverInvalidVersion);
}
// Convert child records to message
var childMsg = new NdefMessage();
if (_handoverAlternativeCarrierRecords != null) childMsg.AddRange(_handoverAlternativeCarrierRecords);
if (_handoverErrorRecord != null) childMsg.Add(_handoverErrorRecord);
var childBytes = childMsg.ToByteArray();
var newPayload = new byte[childBytes.Length + 1];
// Frist byte: handover version
newPayload[0] = _handoverVersion.Version;
// Rest of the payload: child message containing Alternative Carrier records + Error record
Array.Copy(childBytes, 0, newPayload, 1, childBytes.Length);
_payload = newPayload;
}