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它全部開始here。那邊的問題解決了，現在我面臨使用收發方法的問題。NfcA.transceive（byte [] data）throws TagLostException
我的代碼如下所示：
private void writeAndProtectTag(final Intent intent, final String message) {
// Run the entire process in its own thread as NfcA.transceive(byte[] data);
// Should not be run in main thread according to <https://developer.android.com/reference/android/nfc/tech/NfcA.html#transceive(byte[])>
(new Thread(new Runnable() {
// Password has to be 4 characters
// Password Acknowledge has to be 2 characters
byte[] pwd = "-_bA".getBytes();
byte[] pack = "cC".getBytes();
@Override
public void run() {
// Store tag object for use in NfcA and Ndef
Tag tag = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
// Using NfcA instead of MifareUltralight should make no difference in this method
NfcA nfca = null;
// Whole process is put into a big try-catch trying to catch the transceive's IOException
try {
nfca = NfcA.get(tag);
nfca.connect();
byte[] response;
// Authenticate with the tag first
// In case it's already been locked
try {
response = nfca.transceive(new byte[]{
(byte) 0x1B, // PWD_AUTH
pwd[0], pwd[1], pwd[2], pwd[3]
});
// Check if PACK is matching expected PACK
// This is a (not that) secure method to check if tag is genuine
if ((response != null) && (response.length >= 2)) {
byte[] packResponse = Arrays.copyOf(response, 2);
if (!(pack[0] == packResponse[0] && pack[1] == packResponse[1])) {
Toast.makeText(ctx, "Tag could not be authenticated:\n" + packResponse.toString() + "≠" + pack.toString(), Toast.LENGTH_LONG).show();
}
}
}catch(TagLostException e){
e.printStackTrace();
}
// Get Page 2Ah
response = nfca.transceive(new byte[] {
(byte) 0x30, // READ
(byte) 0x2A // page address
});
// configure tag as write-protected with unlimited authentication tries
if ((response != null) && (response.length >= 16)) { // read always returns 4 pages
boolean prot = false; // false = PWD_AUTH for write only, true = PWD_AUTH for read and write
int authlim = 0; // 0 = unlimited tries
nfca.transceive(new byte[] {
(byte) 0xA2, // WRITE
(byte) 0x2A, // page address
(byte) ((response[0] & 0x078) | (prot ? 0x080 : 0x000) | (authlim & 0x007)), // set ACCESS byte according to our settings
0, 0, 0 // fill rest as zeros as stated in datasheet (RFUI must be set as 0b)
});
}
// Get page 29h
response = nfca.transceive(new byte[] {
(byte) 0x30, // READ
(byte) 0x29 // page address
});
// Configure tag to protect entire storage (page 0 and above)
if ((response != null) && (response.length >= 16)) { // read always returns 4 pages
int auth0 = 0; // first page to be protected
nfca.transceive(new byte[] {
(byte) 0xA2, // WRITE
(byte) 0x29, // page address
response[0], 0, response[2], // Keep old mirror values and write 0 in RFUI byte as stated in datasheet
(byte) (auth0 & 0x0ff)
});
}
// Send PACK and PWD
// set PACK:
nfca.transceive(new byte[] {
(byte)0xA2,
(byte)0x2C,
pack[0], pack[1], 0, 0 // Write PACK into first 2 Bytes and 0 in RFUI bytes
});
// set PWD:
nfca.transceive(new byte[] {
(byte)0xA2,
(byte)0x2B,
pwd[0], pwd[1], pwd[2], pwd[3] // Write all 4 PWD bytes into Page 43
});
// Generate NdefMessage to be written onto the tag
NdefMessage msg = null;
try {
NdefRecord r1 = NdefRecord.createMime("text/plain", message.getBytes("UTF-8"));
NdefRecord r2 = NdefRecord.createApplicationRecord("com.example.alex.nfcapppcekunde");
msg = new NdefMessage(r1, r2);
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
byte[] ndefMessage = msg.toByteArray();
nfca.transceive(new byte[] {
(byte)0xA2, // WRITE
(byte)3, // block address
(byte)0xE1, (byte)0x10, (byte)0x12, (byte)0x00
});
// wrap into TLV structure
byte[] tlvEncodedData = null;
tlvEncodedData = new byte[ndefMessage.length + 3];
tlvEncodedData[0] = (byte)0x03; // NDEF TLV tag
tlvEncodedData[1] = (byte)(ndefMessage.length & 0x0FF); // NDEF TLV length (1 byte)
System.arraycopy(ndefMessage, 0, tlvEncodedData, 2, ndefMessage.length);
tlvEncodedData[2 + ndefMessage.length] = (byte)0xFE; // Terminator TLV tag
// fill up with zeros to block boundary:
tlvEncodedData = Arrays.copyOf(tlvEncodedData, (tlvEncodedData.length/4 + 1) * 4);
for (int i = 0; i < tlvEncodedData.length; i += 4) {
byte[] command = new byte[] {
(byte)0xA2, // WRITE
(byte)((4 + i/4) & 0x0FF), // block address
0, 0, 0, 0
};
System.arraycopy(tlvEncodedData, i, command, 2, 4);
try {
response = nfca.transceive(command);
} catch (IOException e) {
e.printStackTrace();
}
}
runOnUiThread(new Runnable() {
@Override
public void run() {
//UI related things, not important for NFC
btn.setImageResource(R.drawable.arrow_red);
tv.setText("");
}
});
curAction = "handle";
try {
nfca.close();
} catch (IOException e) {
e.printStackTrace();
}
} catch (IOException e) {
//Trying to catch any ioexception that may be thrown
e.printStackTrace();
} catch (Exception e) {
//Trying to catch any exception that may be thrown
e.printStackTrace();
}
}
})).start();
}
，所用Ndef類寫上，我沒有這個問題的標籤我的舊代碼版本。現在，我改變了一些東西，我獲得兩個TagLostException S：
- 一個從線PWD_AUTH命令失敗，但它的異常被捕獲，這實際上是打算作爲標籤我掃描沒有密碼尚未設置。
- 另一個來自讀取配置的收發器。
在第二個TagLostException之後，該方法當然結束。閱讀配置時，我不應該得到TagLostException。有人知道那裏發生了什麼嗎？
這裏的例外：
android.nfc.TagLostException: Tag was lost.
at android.nfc.TransceiveResult.getResponseOrThrow(TransceiveResult.java:48)
at android.nfc.tech.BasicTagTechnology.transceive(BasicTagTechnology.java:151)
at android.nfc.tech.NfcA.transceive(NfcA.java:129)
at com.example.alex.nfcapppce.MainActivity$2.run(MainActivity.java:134)
at java.lang.Thread.run(Thread.java:761)
android.nfc.TagLostException: Tag was lost.
at android.nfc.TransceiveResult.getResponseOrThrow(TransceiveResult.java:48)
at android.nfc.tech.BasicTagTechnology.transceive(BasicTagTechnology.java:151)
at android.nfc.tech.NfcA.transceive(NfcA.java:129)
at com.example.alex.nfcapppce.MainActivity$2.run(MainActivity.java:155)
at java.lang.Thread.run(Thread.java:761)