how to use MifareClassic API “Increment” and “Decrement” in android?

Question

My problem is when i called the MifareClassic function "increment", it will return "Increment success", but while i check the value block , it's doen't have any increment for the value , are there have any wrong using in my code ?

my code is as below :

   try {
     mfc.increment(0x14,increvalue);
     metaInfo =  "Increment Success !";
     mfc.close();
   } catch (IOException e) {
     e.printStackTrace();
     metaInfo = "Increment Fail!";
   }

Answer 1

The mifare increment and decrement functions do the calculation on the tag but don't write the result back to persistent memory.

Instead the result will be stored in a temporary register on the tag.

To write the result back to the tag use the transfer function:

http://developer.android.com/reference/android/nfc/tech/MifareClassic.html#transfer%28int%29

Note that you may pass a different block index for increment and transfer to implement a function that adds/subtracts from block X and writes the result into block Y.