[英]Write ndef message to NFC Tag fails with java.io.exception
[英]How to write NDEF records to NFC tag?
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,我有代码来生成 NDEF 消息:
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;
}
我如何发现 TAG? 有人可以帮我吗?
我会忽略什么谷歌文件说,在阅读https://developer.android.com/guide/topics/connectivity/nfc/nfc和在读/写https://developer.android.com/guide/topics/连接/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,您应该使用更新更好的enableReaderMode
API https://developer.android.com/reference/android/nfc/NfcAdapter
使用这个较新的 API 会导致写入失败和卡损坏的情况减少很多,因为您可以控制通知声音何时发生。 在旧的基于Intent
的系统中,系统 App 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采用卡方式,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读取 NFC 卡,然后您可以读写卡,然后当您成功写入卡时,您可以自己发出通知声音.
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。 需要额外的逻辑来避免每次出示单张牌或出示不同牌时都写入相同的消息。
一些示例代码(改编自我的应用程序,NFC 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
}
}
}
}
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