Android 11 完整代码实现NFC和读卡器连接

以下是一个简单的Android 11 NFC和读卡器连接的实现示例：

1. 添加NFC权限和NFC功能到AndroidManifest.xml文件中：

<uses-permission android:name="android.permission.NFC" />

<uses-feature android:name="android.hardware.nfc" android:required="true"/>

2. 在你的Activity中，创建一个NFC adapter对象：

NfcAdapter nfcAdapter = NfcAdapter.getDefaultAdapter(this);

3. 确认读卡器连接：

if (nfcAdapter != null && nfcAdapter.isEnabled()) {
    Toast.makeText(this, "NFC is available", Toast.LENGTH_LONG).show();
} else {
    Toast.makeText(this, "NFC is not available", Toast.LENGTH_LONG).show();
}

4. 创建一个NFC读取intent：

private PendingIntent createPendingIntent() {
    Intent intent = new Intent(this, getClass());
    intent.addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP);
    return PendingIntent.getActivity(this, 0, intent, 0);
}

5. 处理NFC读取intent：

@Override
protected void onResume() {
    super.onResume();
    Intent intent = getIntent();
    if (NfcAdapter.ACTION_NDEF_DISCOVERED.equals(intent.getAction())) {
        Parcelable[] rawMessages =
                intent.getParcelableArrayExtra(NfcAdapter.EXTRA_NDEF_MESSAGES);
        if (rawMessages != null) {
            NdefMessage[] messages = new NdefMessage[rawMessages.length];
            for (int i = 0; i < rawMessages.length; i++) {
                messages[i] = (NdefMessage) rawMessages[i];
            }
            if (messages.length > 0) {
                String message = new String(messages[0].getRecords()[0].getPayload());
                Log.d(TAG, "NFC message received: " + message);
            }
        }
    }
}

6. 在onCreate()方法中启动NFC读取：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    PendingIntent pendingIntent = createPendingIntent();
    IntentFilter[] intentFilters = new IntentFilter[]{new IntentFilter(NfcAdapter.ACTION_NDEF_DISCOVERED)};
    nfcAdapter.enableForegroundDispatch(this, pendingIntent, intentFilters, null);
}

7. 在onPause()方法中停止NFC读取：

@Override
protected void onPause() {
    super.onPause();
    nfcAdapter.disableForegroundDispatch(this);
}

8. 为了连接读卡器，你需要使用UsbManager和一个BroadcastReceiver：

private static final String ACTION_USB_PERMISSION = "com.android.example.USB_PERMISSION";

private UsbManager usbManager;
private UsbDevice usbDevice;

private final BroadcastReceiver usbBroadcastReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        switch (action) {
            case ACTION_USB_PERMISSION:
                UsbDevice device = intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
                boolean permissionGranted = intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false);
                if (device != null && permissionGranted) {
                    if (device.equals(usbDevice)) {
                        // 连接读卡器
                        // ...
                    }
                }
                break;
        }
    }
};

9. 在onCreate()方法中初始化UsbManager和读卡器：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    
    usbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
    IntentFilter filter = new IntentFilter();
    filter.addAction(ACTION_USB_PERMISSION);
    registerReceiver(usbBroadcastReceiver, filter);
    
    // 查找和连接读卡器
    findAndConnectUsbDevice();
}

private void findAndConnectUsbDevice() {
    HashMap<String, UsbDevice> usbDevices = usbManager.getDeviceList();
    if (!usbDevices.isEmpty()) {
        for (UsbDevice device : usbDevices.values()) {
            if (isSupported(device)) {
                PendingIntent permissionIntent = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0);
                usbManager.requestPermission(device, permissionIntent);
                usbDevice = device;
                break;
            }
        }
    }
}

private boolean isSupported(UsbDevice device) {
    // 检查设备是否支持读卡器的VID和PID
    // ...
    return true;
}

10. 在onDestroy()方法中，注销BroadcastReceiver：

@Override
protected void onDestroy() {
    super.onDestroy();
    unregisterReceiver(usbBroadcastReceiver);
}

这个示例可以帮助你开始使用NFC和读卡器连接，但具体实现还需要根据你的需求进行调整和拓展。