我试图在空的NTAG213标签上设置密码，但是当我编写PACK和PWD时，我的应用程序只是崩溃，没有异常抛出。我确实得到我的应用程序远远足以编写有效的NDEF消息并读取它们，似乎我也可以写入其他配置页面（2Ah和29h用于配置密码保护）。当我开始编写PACK时，我的应用程序崩溃但没有抛出我期望的MifareUltralight.transceive（byte []数据）的IOException。
这是我的writeAndProtect方法的源代码：
private void writeAndProtectTag(final Intent intent, final String message) {
// Run the entire process in its own thread as MifareUltralight.transceive(byte[] data);
// Should not be run in main thread according to <https://developer.android.com/reference/android/nfc/tech/MifareUltralight.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 MifareUltralight and Ndef
Tag tag = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
MifareUltralight mifare = null;
int debugCounter = 0;
// Whole process is put into a big try-catch trying to catch the transceive's IOException
try {
mifare = MifareUltralight.get(tag);
mifare.connect();
while(!mifare.isConnected());
byte[] response;
// Authenticate with the tag first
// In case it's already been locked
try {
response = mifare.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(IOException e){
e.printStackTrace();
}
// Get Page 2Ah
response = mifare.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
mifare.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 = mifare.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
mifare.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:
mifare.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:
mifare.transceive(new byte[] {
(byte)0xA2,
(byte)0x2B,
pwd[0], pwd[1], pwd[2], pwd[3] // Write all 4 PWD bytes into Page 43
});
} catch (IOException e) {
//Trying to catch any exception that may be thrown
e.printStackTrace();
} catch (Exception e) {
//Trying to catch any exception that may be thrown
e.printStackTrace();
}
try {
mifare.close();
} catch (IOException e) {
e.printStackTrace();
}
// 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.myname.myapplication");
msg = new NdefMessage(r1, r2);
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
// Generate Ndef object from tag object
Ndef ndef = Ndef.get(tag);
// Connect NDEF, write message and close connection
try {
ndef.connect();
ndef.writeNdefMessage(msg);
ndef.close();
} catch (IOException e) {
e.printStackTrace();
} catch (FormatException e) {
e.printStackTrace();
} catch (Exception e) {
//Trying to catch any exception that may be thrown
e.printStackTrace();
}
runOnUiThread(new Runnable() {
@Override
public void run() {
btn.setImageResource(R.drawable.arrow_red);
tv.setText("");
}
});
curAction = "handle";
}
})).start();
}
编辑：我不知道昨天Android Studio是否出现问题，或者您的解决方案是否真的改变了这种情况，但我更新了代码，现在得到以下异常：
E/AndroidRuntime: FATAL EXCEPTION: Thread-4
Process: com.example.alex.nfcapppce, PID: 25918
java.lang.IllegalStateException: Close other technology first!
at android.nfc.Tag.setConnectedTechnology(Tag.java:458)
at android.nfc.tech.BasicTagTechnology.connect(BasicTagTechnology.java:78)
at android.nfc.tech.Ndef.connect(Ndef.java)
at com.example.alex.nfcapppce.MainActivity$2.run(MainActivity.java:194) //The line saying ndef.connect()
at java.lang.Thread.run(Thread.java:761)
我不太明白为什么会这样开心，因为首先我连接mifare，等到它连接，进行收发，关闭我的mifare然后用ndef.connect（）阻止调用。这是否意味着在我的收发块中的某个地方我得到了一个例外，因此我没有正确关闭mifare并且无法打开ndef？这很奇怪，因为我没有得到异常，即使我只用Exception换掉了IOException，所以无论确切的类型如何，我都会捕获每个异常。
编辑2 ：我现在知道应用程序在此异常中结束的原因。代码实际上工作，我的标签现在用密码保护，当我再次尝试使用相同的标签时，我首先不进行身份验证，因此收发失败，导致try-catch块的中断，该块也包含close函数。我通过在整个线程中使用MifareUltralight对象并在运行ndef.connect（）部分之前关闭它来解决这个问题。
现在我的（希望）最后一个问题是：我可以使用Ndef类进行身份验证吗？我的Ndef对象似乎没有一个验证方法，所以我必须再次使用MifareUltralight。但是当我关闭MifareUltralight连接以打开Ndef连接时，身份验证不会丢失？或者是我唯一可能使用密码保护标记写Ndef消息 使用MifareUltralight.writepage（byte [] addr，byte []数据）将字符串切割成4字节页并一个接一个地写入？当我使用上面更新时，我从ndef.writeNdefMessage（）得到一个IOException，我想这意味着关闭mifare连接也是unauth＆＃39; d。
提前致谢。
答案 0 :(得分：1)
使用MifareUltralight技术时，您永远不会连接到标签。因此，调用mifare.transceive()将导致异常。您的应用程序崩溃，因为此异常可能不是IOException的实例（您将在代码中捕获该实例）。
因此，请务必致电
mifare.connect();
，并确保在此之后再次关闭实例：
try {
mifare.close();
} catch (Exception ignored) {}