I would like to know how to append some text to an NFC tag on Android. I know that writeNdefMessage can overwrite the the whole message on the tag but I did not find any method to append data to it. However, I would prefer to append it.
If you want to stick to high-level (tag platform independent) access to NFC tags through the Ndef class, then you can only overwrite the whole NDEF message using writeNdefMessage().
Android also permits you to directly send low-level commands to NFC tags (e.g. to issue a read/write command). You could use such commands to append data to a free memory area on the tag. However, how you would do this heavily depends to the tag platform that you use.