我正在从我的应用程序发送数据到热敏打印机。我已经让它在网络上正常工作，我的数据也能正确打印。现在有了一个额外的要求，我们也必须能够通过usb打印。
以下是我尝试过的方法：

private UsbManager mUsbManager;
    private UsbDevice mDevice;
    private UsbDeviceConnection mConnection;
    private UsbInterface mInterface;
    private UsbEndpoint mEndPoint;
    private PendingIntent mPermissionIntent;
    private static final String ACTION_USB_PERMISSION = "com.android.example.USB_PERMISSION";
    private static Boolean forceCLaim = true;

    HashMap<String, UsbDevice> mDeviceList;
    Iterator<UsbDevice> mDeviceIterator;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my);

        mUsbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
        mDeviceList = mUsbManager.getDeviceList();    
        mDeviceIterator = mDeviceList.values().iterator();

        Button print = (Button)findViewById(R.id.print);

        Toast.makeText(this, "Device List Size: " + String.valueOf(mDeviceList.size()), Toast.LENGTH_SHORT).show();
        TextView textView = (TextView) findViewById(R.id.usbDevice);
        String usbDevice = "";
        //This is just testing what devices are connected
        while (mDeviceIterator.hasNext()) {
            UsbDevice usbDevice1 = mDeviceIterator.next();
            usbDevice += "\n" +
                    "DeviceID: " + usbDevice1.getDeviceId() + "\n" +
                    "DeviceName: " + usbDevice1.getDeviceName() + "\n" +
                    "DeviceClass: " + usbDevice1.getDeviceClass() + " - " + translateDeviceClass(usbDevice1.getDeviceClass()) + "\n" +
                    "DeviceSubClass: " + usbDevice1.getDeviceSubclass() + "\n" +
                    "VendorID: " + usbDevice1.getVendorId() + "\n" +
                    "ProductID: " + usbDevice1.getProductId() + "\n";

            int interfaceCount = usbDevice1.getInterfaceCount();
            Toast.makeText(this, "INTERFACE COUNT: " + String.valueOf(interfaceCount), Toast.LENGTH_SHORT).show();

            mDevice = usbDevice1;

            if (mDevice == null) {
                Toast.makeText(this, "mDevice is null", Toast.LENGTH_SHORT).show();
            }else{
                Toast.makeText(this, "mDevice is not null", Toast.LENGTH_SHORT).show();
            }
            textView.setText(usbDevice);
        }

        if (mDevice == null) {
            Toast.makeText(this, "mDevice is null", Toast.LENGTH_SHORT).show();
        }else{
            Toast.makeText(this, "mDevice is not null", Toast.LENGTH_SHORT).show();
        }

        mPermissionIntent = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0);
        IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
        registerReceiver(mUsbReceiver, filter);
        mUsbManager.requestPermission(mDevice, mPermissionIntent);

  print.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                //setup();
                print(mConnection, mInterface);
            }
        });
}

   private String translateDeviceClass(int deviceClass){
        switch(deviceClass){
            case UsbConstants.USB_CLASS_APP_SPEC:
                return "Application specific USB class";
            case UsbConstants.USB_CLASS_AUDIO:
                return "USB class for audio devices";
            case UsbConstants.USB_CLASS_CDC_DATA:
                return "USB class for CDC devices (communications device class)";
            case UsbConstants.USB_CLASS_COMM:
                return "USB class for communication devices";
            case UsbConstants.USB_CLASS_CONTENT_SEC:
                return "USB class for content security devices";
            case UsbConstants.USB_CLASS_CSCID:
                return "USB class for content smart card devices";
            case UsbConstants.USB_CLASS_HID:
                return "USB class for human interface devices (for example, mice and keyboards)";
            case UsbConstants.USB_CLASS_HUB:
                return "USB class for USB hubs";
            case UsbConstants.USB_CLASS_MASS_STORAGE:
                return "USB class for mass storage devices";
            case UsbConstants.USB_CLASS_MISC:
                return "USB class for wireless miscellaneous devices";
            case UsbConstants.USB_CLASS_PER_INTERFACE:
                return "USB class indicating that the class is determined on a per-interface basis";
            case UsbConstants.USB_CLASS_PHYSICA:
                return "USB class for physical devices";
            case UsbConstants.USB_CLASS_PRINTER:
                return "USB class for printers";
            case UsbConstants.USB_CLASS_STILL_IMAGE:
                return "USB class for still image devices (digital cameras)";
            case UsbConstants.USB_CLASS_VENDOR_SPEC:
                return "Vendor specific USB class";
            case UsbConstants.USB_CLASS_VIDEO:
                return "USB class for video devices";
            case UsbConstants.USB_CLASS_WIRELESS_CONTROLLER:
                return "USB class for wireless controller devices";
            default: return "Unknown USB class!";
        }
//Broadcast receiver to obtain permission from user for connection
 private final BroadcastReceiver mUsbReceiver = new BroadcastReceiver() {

        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (ACTION_USB_PERMISSION.equals(action)) {
                synchronized (this) {
                    UsbDevice device = (UsbDevice)intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);

                    if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)) {
                        if(device != null){
                            //call method to set up device communication
                            mInterface = device.getInterface(0);
                            mEndPoint = mInterface.getEndpoint(0);
                            mConnection = mUsbManager.openDevice(device);

                            //setup();
                        }
                    }
                    else {
                        //Log.d("SUB", "permission denied for device " + device);
                        Toast.makeText(context, "PERMISSION DENIED FOR THIS DEVICE", Toast.LENGTH_SHORT).show();
                    }
                }
            }
        }
    };

 private void print(UsbDeviceConnection connection, UsbInterface intrface){

        String test = "THIS IS A PRINT TEST";
        byte [] testBytes = test.getBytes();

        if(intrface==null){
            Toast.makeText(this, "INTERFACE IS NULL", Toast.LENGTH_SHORT).show();
        }
        if(connection==null){
            Toast.makeText(this, "CONNECTION IS NULL", Toast.LENGTH_SHORT).show();
        }

        if(forceCLaim==null){
            Toast.makeText(this, "FORCE CLAIM IS NULL", Toast.LENGTH_SHORT).show();
        }   

        connection.claimInterface(intrface, forceCLaim);
        connection.bulkTransfer(mEndPoint, testBytes, testBytes.length, 0);

    }

因此，设备连接到usb设备，但当我尝试bulktransfer什么都没有发生，有人能阐明这一点吗？Usb连接对我来说是一个新的领域，所以任何提示都不胜感激

编辑
原来端点有问题，批量传输没有返回，但是，现在这些问题解决了，它返回批量传输成功，但是，它仍然没有打印。有人对此有什么想法吗？