Android Open Source - sodf Nfc Handler

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License

The source code is released under:

Copyright (c) 2013 Lorenz Lehmann Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Sof...

Java Source Code

package lal.sodf.framework.nfc;
//w  w  w  .j av  a  2 s .c  o  m
import java.io.IOException;
import java.nio.charset.Charset;

import lal.sodf.framework.exceptions.MalformedTypeException;
import lal.sodf.framework.exceptions.TagEmptyException;
import lal.sodf.framework.exceptions.UnformattedTagException;
import android.nfc.FormatException;
import android.nfc.NdefMessage;
import android.nfc.NdefRecord;
import android.nfc.Tag;
import android.nfc.TagLostException;
import android.nfc.tech.Ndef;
import android.nfc.tech.NdefFormatable;

/**
 * A class to read or write data from NFC tags with the help of the Android libraries
 * @author Lorenz Lehmann
 *
 */
public class NfcHandler {
  /** The type parameter which is used if the app does not provide its package name */
  public static final String UNKNOWN_APP = "unknown";
  
  /**
   * Write data on a NFC tag
   * @param tag The tag where the data is written on
   * @param app A string to identify the app. This should be the package name of the application under which it is listend in the Google Play store
   * @param payload The payload, which will be written on the tag
   * @param compression The compression algorithm or null if no compression was used
   * @throws IOException If there is an I/O failure, or the operation is canceled when reading from the tag
   * @throws FormatException If the NDEF Message on the tag is malformed
   * @throws TagLostException If the device is moved away from the tag during the read
   */
  public static void writeData(Tag tag, String app, byte[] payload, String compression) throws TagLostException, IOException, FormatException{
    Ndef ndef = null;
    NdefFormatable formattable = null;
    try {
      //build the type description
      String type = "sodf/";

      if (compression != null) type = type + compression + "/";

      if (app != null && app.length() > 0) type = type + app;
      else type = type + UNKNOWN_APP;

      //build the NDEF record, which can be written on the tag
      NdefRecord record = new NdefRecord(
          NdefRecord.TNF_MIME_MEDIA ,
          type.getBytes(Charset.forName("UTF-8")),
          new byte[0],
          payload); 

      //put the NDEF record in a message
      NdefRecord[] records = { record };
      NdefMessage  message = new NdefMessage(records);
      // Get an instance of Ndef for the tag.
      ndef = Ndef.get(tag);
      //if the tag was not formatted yet it will be null
      if (ndef == null) {
        //try to format the tag
        formattable = NdefFormatable.get(tag);
        formattable.connect();
        formattable.format(message);
        formattable.close();
      }
      else {//if the tag is formatted just write the data
        // Enable I/O
        ndef.connect();
        // Write the message
        ndef.writeNdefMessage(message);
        // Close the connection
        ndef.close();        
      }
    }
    finally {//always close used connections
      if (ndef != null) ndef.close();
      if (formattable != null) formattable.close();      
    }
  }
  
  /**
   * Read data from an NFC tag
   * @param tag The tag where the data is read from
   * @return The data, which was read from the tag
   * @throws IOException If there is an I/O failure, or the operation is canceled when reading from the tag
   * @throws FormatException If the NDEF Message on the tag is malformed
   * @throws TagLostException If the device is moved away from the tag during the read
   * @throws MalformedTypeException If the type of the NDEF message is not in the format sodf/ * or sodf/ * / * 
   * @throws UnformattedTagException If the tag is not formatted
   * @throws TagEmptyException If the tag is empty and nod NDEF messages have been written on it
   */
  public static NfcContentWrapper readData(Tag tag) throws TagLostException, IOException, FormatException, MalformedTypeException, UnformattedTagException, TagEmptyException{
    Ndef ndef = null;
    try {
      //get the NDEF record from the tag
      ndef = Ndef.get(tag);
      if (ndef == null) throw new UnformattedTagException();
      ndef.connect();
      //get the message from the tag
      NdefMessage msg = ndef.getNdefMessage();
      if (msg == null) throw new TagEmptyException("Tag contains no NDEF message. Was anything written on it?");
      //close the connection again
      ndef.close();
      
      //parse the NDEF records    
      NdefRecord[] records = msg.getRecords();
      if (records.length <= 0) throw new TagEmptyException("Tag does not contain any data.");
      NdefRecord record = records[0];//there should be only one record since we only write one
      
      //parse the content of the record
      NfcContentWrapper ncw = new NfcContentWrapper();    
      //get the type
      String type = new String(record.getType(), Charset.forName("UTF-8"));
      String[] typeParts = type.split("/");
      if (typeParts.length == 2){//no compression used
        ncw.app = typeParts[1];
      }
      else if (typeParts.length == 3){//compression used
        ncw.compression = typeParts[1];
        ncw.app = typeParts[2];
      }
      else {//the tag is not formatted properly
        throw new MalformedTypeException("Malformed type: "+type);
      }
      //get the payload
      ncw.payload = record.getPayload();
      
      return ncw;      
    }
    finally {//always close the connection, even if an exception occurs
      if (ndef != null) ndef.close();      
    }
  }
}

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