Not able to format NFC card using NdefFormatable(无法使用 NdefFormatable 格式化 NFC 卡)
问题描述
I am using NdefFormatable class to format my NFC card. The code is like:
NdefFormatable formatable=NdefFormatable.get(tag);
But i get formatable reference as null. I checked the code that is run inside the get(tag) method. It checks:
if (!tag.hasTech(TagTechnology.NDEF_FORMATABLE)) return null;
I ran "tag.getTechList()" for my tag. I got:
android.nfc.tech.NfcA
android.nfc.tech.Ndef
I was able to format this card using Trigger application.
What can be done to format this.
The NdefFormatable
and the Ndef
tag technologies are mutually exclusive. Either your tag is not yet NDEF formatted (i.e. it is not yet prepared to store NDEF messages) or it is already prepared to store NDEF messages (and already contains (at least an empty) an NDEF message).
So NdefFormatable
is only used for writing an initial NDEF message to a tag.
As your tag already lists the android.nfc.tech.Ndef
technology, it is already prepared to store an NDEF message and does not need further formatting. You can simply overwrite (given that the tag is not read-only) any existing NDEF message by using the writeNdefMessage()
method of the Ndef
object. E.g. to "format" the tag to an empty NDEF message, you could do something like:
Ndef ndefTag = Ndef.get(tag);
ndefTag.writeNdefMessage(new NdefMessage(new NdefRecord(NdefRecord.TNF_EMPTY, null, null, null)));
Update:
On devices with the libnfc-nci NFC stack, it seems that NdefFormatable
and Ndef
tag technologies are no longer mutually exclusive. Formatted tags will (sometimes?) be enumerated as both NdefFormatable
and Ndef
. In thoses cases, you would still typically try to use the Ndef
first and only if that fails use the NdefFormatable
object.
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本文标题为:无法使用 NdefFormatable 格式化 NFC 卡
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