How to make an android app which can write Mifare classic Tag?

I try to make an App to write with my Nexus S to an unforamted Mifare Classic Tag. No NDEF but any bytes! With this Explenation i can allready read the hole Card (included the UID) but i cant write anything to the Card. Reading a MiFare Classic 1K from Android using Nexus S.

How is it possible? I Hope You can help me :)

I have authenticate开发者_C百科d me in every secotor, read every Sector but can't write to the Sectors. Please Help me, it's very important!

Greeting, Jules :)

You can write a tag by using this after the authentication process : mfc.writeBlock(6,value) where 6 implies the block number of the sector you have authenticated. The value is the byte array of the data you want to write in to the mifare card.Please note that the length of the byte array has to be 16 bytes in length.If lesser pad it with zeroes or null values but make sure you have the 16 bytes length.hope your answer is replied.:)

With the Mifare SDK you can communicate with a few NFC cards. Have a look: Mifare SDK introduction