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;
}

如何发现标签？ 有人可以帮我吗？

Answer 1

我会忽略谷歌文档所说的阅读内容 https://developer.android.com/guide/topics/connectivity/nfc/nfc 以及读/写内容 https://developer.android.com/ Guide/topics/connectivity/nfc/advanced-nfc#read-write 因为这为写入标签提供了非常差的用户体验，并由于用户行为导致大量写入失败。

要使用 Android 可靠地写入 NFC，您应该使用更新且更好的

enableReaderMode

API https://developer.android.com/reference/android/nfc/NfcAdapter

使用这个较新的 API 可以大大减少写入失败和卡损坏的情况，因为您可以控制通知声音何时发生。使用旧的基于

Intent

的系统，系统会暂停您的应用程序，然后读取卡并发出通知声音，然后用户在您的应用程序恢复之前移除卡，并有机会处理卡数据并写入卡。

使用较新的

enableReaderMode

API，您可以关闭系统通知声音，并且您的应用程序永远不会暂停来读取 NFC 卡，然后您可以读取和写入卡，然后当您成功写入卡时，您可以使自己发出通知声音。

因为任何错误都是无声的，用户将不断尝试出示卡片，直到成功通知。需要额外的逻辑，以免每次出示一张卡片或不同的卡片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，用于处理低级读写（不是 Ndef 标签技术））

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
      } 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
             }
      }

   }

}