如何将NDEF记录写入NFC标签

Question

如何将NDEF消息写入NFC标签？我必须更改清单文件吗？到目前为止，我有生成NDEF消息的代码：

public NdefRecord createTextRecord(String payload, Locale locale, boolean encodeInUtf8) {
byte[] langBytes = locale.getLanguage().getBytes(Charset.forName("US-ASCII"));
Charset utfEncoding = encodeInUtf8 ? Charset.forName("UTF-8") : Charset.forName("UTF-16");
byte[] textBytes = payload.getBytes(utfEncoding);
int utfBit = encodeInUtf8 ? 0 : (1 << 7);
char status = (char) (utfBit + langBytes.length);
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);
NdefRecord record = new NdefRecord(NdefRecord.TNF_WELL_KNOWN,
NdefRecord.RTD_TEXT, new byte[0], data);
return record;
}

如何发现TAG？有人能帮我吗？

Answer 1

我会忽略谷歌文档中关于阅读的内容https://developer.android.com/guide/topics/connectivity/nfc/nfc和的读/写https://developer.android.com/guide/topics/connectivity/nfc/advanced-nfc#read-写，因为这为写标签提供了非常糟糕的用户体验，并且由于用户行为导致了许多失败的写操作。

为了使用Android获得NFC的可靠写入，您应该使用更新更好的enableReaderModeAPIhttps://developer.android.com/reference/android/nfc/NfcAdapter

使用这种新的API可以减少失败的写入和损坏的卡，因为您可以控制何时发出通知声音。在旧的基于Intent的系统中，系统会暂停您的应用程序，然后读取卡并发出通知声音，然后用户在恢复应用程序之前取出卡，并有机会处理卡数据并写入卡。

使用较新的enableReaderModeAPI，您可以关闭系统通知声音，并且您的应用程序从未暂停读取NFC卡，然后您可以读取和写入卡，然后当您成功写入卡时，您可以自己发出通知声音。

由于任何错误都是静默的，用户将继续尝试出示卡，直到成功通知。需要额外的逻辑，以避免每次出现单个卡或不同的卡时都写入相同的消息。

一些示例代码(改编自我的NFC应用程序，用于处理低级别的读写(不是Ndef Tag技术((

public class NFCActivity extends AppCompatActivity implements NfcAdapter.ReaderCallback{
private NfcAdapter mNfcAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_nfc);
mNfcAdapter = NfcAdapter.getDefaultAdapter(this);
// Rest of Activity setup
}
@Override
protected void onResume() {
super.onResume();
if(mNfcAdapter!= null) {
Bundle options = new Bundle();
// Work around for some broken Nfc firmware implementations that poll the card too fast
options.putInt(NfcAdapter.EXTRA_READER_PRESENCE_CHECK_DELAY, 250);
// Enable ReaderMode for all types of card and disable platform sounds
mNfcAdapter.enableReaderMode(this,
this,
NfcAdapter.FLAG_READER_NFC_A |
NfcAdapter.FLAG_READER_NFC_B |
NfcAdapter.FLAG_READER_NFC_F |
NfcAdapter.FLAG_READER_NFC_V |
NfcAdapter.FLAG_READER_NFC_BARCODE |
NfcAdapter.FLAG_READER_NO_PLATFORM_SOUNDS,
options);
}
}
@Override
protected void onPause() {
super.onPause();
if(mNfcAdapter!= null)
mNfcAdapter.disableReaderMode(this);
}

// This method is run in another thread when a card is discovered
// !!!! This method cannot cannot direct interact with the UI Thread
// Use `runOnUiThread` method to change the UI from this method
public void onTagDiscovered(Tag tag) {
// Read and or write to Tag here to the appropriate Tag Technology type class
// in this example the card should be an Ndef Technology Type 
Ndef mNdef = Ndef.get(tag);
// Check that it is an Ndef capable card
if (mNdef!= null) {
// If we want to read
// As we did not turn on the NfcAdapter.FLAG_READER_SKIP_NDEF_CHECK
// We can get the cached Ndef message the system read for us.
NdefMessage mNdefMessage = mNdef.getCachedNdefMessage();

// Or if we want to write a Ndef message
// Create a Ndef Record
NdefRecord mRecord = NdefRecord.createTextRecord("en","English String");
// Add to a NdefMessage
NdefMessage mMsg = new NdefMessage(mRecord);

// Catch errors
try {
mNdef.connect();
mNdef.writeNdefMessage(mMsg);
// Success if got to here
runOnUiThread(() -> {
Toast.makeText(getApplicationContext(),
"Write to NFC Success",
Toast.LENGTH_SHORT).show();
});
// Make a Sound
try {
Uri notification = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
Ringtone r = RingtoneManager.getRingtone(getApplicationContext(),
notification);
r.play();
} catch (Exception e) {
// Some error playing sound
}

} catch (FormatException e) {
// if the NDEF Message to write is malformed
} catch (TagLostException e) {
// Tag went out of range before operations were complete
} catch (IOException e){
// if there is an I/O failure, or the operation is cancelled
} catch (SecurityException e){
// The SecurityException is only for Android 12L and above
// The Tag object might have gone stale by the time
// the code gets to process it, with a new one been
// delivered (for the same or different Tag)
// The SecurityException is thrown if you are working on
// a stale Tag
} finally {
// Be nice and try and close the tag to
// Disable I/O operations to the tag from this TagTechnology object, and release resources. 
try {
mNdef.close();
} catch (IOException e) {
// if there is an I/O failure, or the operation is cancelled
}
}
}
}