Character problems coming in Ndefmessage NFC

Question

I am making a program that exchanges messages for NFC, and I am having a problem that when I want to pass a Parameter in the message appears all right now when I want to pass 2 parameters, so there is one that always appears with characters this in the Tlm that receives the message.

I’ll show you my source.

Code of the class sending the message:

    NdefMessage create_RTD_TEXT_NdefMessage(String cumprimento,String ID)
{

    Locale locale = new Locale("en", "US");
    byte[] langBytes = locale.getLanguage().getBytes(Charset.forName("US-ASCII"));

    boolean encodeInUtf8 = false;
    Charset utfEncoding = encodeInUtf8 ? Charset.forName("UTF-8") : Charset.forName("UTF-16");
    int utfBit = encodeInUtf8 ? 0 : (1 << 7);
    byte status = (byte) (utfBit + langBytes.length);

    byte[] textBytes = cumprimento.getBytes(utfEncoding);
    byte[] data = new byte[1 + langBytes.length + textBytes.length];

    data[0] = (byte) status;
    System.arraycopy(langBytes, 0, data, 1, langBytes.length);
    System.arraycopy(textBytes, 0, data, 1 + langBytes.length, textBytes.length);


    Locale locale2 = new Locale("en", "US");
    byte[] langBytes2 = locale2.getLanguage().getBytes(Charset.forName("US-ASCII"));
    boolean encodeInUtf8_ = false;
    Charset utfEncoding2 = encodeInUtf8_ ? Charset.forName("UTF-8") : Charset.forName("UTF-16");
    int utfBit2 = encodeInUtf8_ ? 0 : (1 << 7);
    byte status2 = (byte) (utfBit2 + langBytes2.length);

    byte[] textBytes2 = ID.getBytes(utfEncoding2);
    byte[] data2 = new byte[1 + langBytes2.length + textBytes2.length];

    data[0] = (byte) status2;
    System.arraycopy(langBytes2, 0, data2, 1, langBytes2.length);
    System.arraycopy(textBytes2, 0, data2, 1 + langBytes2.length, textBytes2.length);


    NdefRecord textRecord = new NdefRecord(NdefRecord.TNF_WELL_KNOWN, NdefRecord.RTD_TEXT, new byte[0], data);
    NdefRecord textRecord2 = new NdefRecord(NdefRecord.TNF_WELL_KNOWN, NdefRecord.RTD_TEXT, new byte[0], data2);

    NdefMessage message = new NdefMessage(textRecord, textRecord2);

    return message;

}

And now the class that receives the NFC message:

   void processIntent(Intent intent) {

         NdefMessage[] messages = getNdefMessages(getIntent());
         for(int i=0; i <messages.length; i++){
             for(int j=0;j< messages[0].getRecords().length;j++){

                NdefRecord record = messages[i].getRecords()[j];
                 int languageCodeLength= statusByte & 0x3F; //mask value in order to find language code length 
                 int isUTF8=statusByte-languageCodeLength;

                if(j == 0)
                    {
                         statusByte=record.getPayload()[0];

                         if(isUTF8==0x00){
                            ammount=new String(record.getPayload(),1+languageCodeLength,record.getPayload().length-1-languageCodeLength,Charset.forName("UTF-8"));
                            System.out.println(ammount + "***********");
                         }
                         else if (isUTF8==-0x80){
                            cumprimento = new String(record.getPayload(),1+languageCodeLength,record.getPayload().length-1-languageCodeLength,Charset.forName("UTF-16"));
                         }
                    }

                if(j == 1)
                     {
                         statusByte1 = record.getPayload()[0];

                         if(isUTF8==0x00){
                            id = new String(record.getPayload(),1+languageCodeLength,record.getPayload().length-1-languageCodeLength,Charset.forName("UTF-8"));
                         }
                         else if (isUTF8==-0x80){
                            id = new String(record.getPayload(),1+languageCodeLength,record.getPayload().length-1-languageCodeLength,Charset.forName("UTF-16"));

                         }
                    }
                Valor = (TextView) this.findViewById(R.id.Valor ); 
                Valor.setText("Montante a pagar \n" + "€ "  + cumprimento);
             }
         }
    }

The problem that is happening is that one of the values in the IF goes through the UTF-8 and appears characters that should not and the other appears in the UTF-16 and appears all right.

Somebody help me with this problem?

Answer 1

statusByte seems to be being used before being assigned in Decoder. Since the declared variable starts with zero, the Decoder must be assuming UTF-16 in the first round.

I don’t like this math either:

           int isUTF8=statusByte-languageCodeLength;

but it seems to be correct. I simulated here with a UTF-8 string of length 5 would be 0x85, when converted to integer it turns negative -0x7b, which decreased from 5 actually reaches the value -0x80.