我正在创建一个 android 应用程序，其中包含来自通过 USB 连接的打印机的打印数据。在这里，我想设置页面布局，例如到达页面末尾时的换行打印和页面边框等。是否可以通过编程方式进行。请帮助我如何做到这一点。
这是我为打印数据所做的：
public class DemoPrinter extends Activity {
private final String ACTION_USB_PERMISSION = "com.android.example.USB_PERMISSION";
Button create_file;
PendingIntent mPermissionIntent;
UsbManager usbManager;
UsbDevice device;
EditText print_text;
UsbDevice printer = null;
private static final int PRINTER_VENDOR_ID = 1256;
private String filename = "MySampleFile.txt";
private String filepath = "PanelFilesstorage";
File myInternalFile;
String data= "This is a sample text";
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
try
{
setContentView(R.layout.activity_demo_printer);
ContextWrapper contextWrapper = new ContextWrapper(getApplicationContext());
File directory = contextWrapper.getDir(filepath, Context.MODE_PRIVATE);
myInternalFile = new File(directory , filename);
print_text = (EditText)findViewById(R.id.editText_printer);
usbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
HashMap<String, UsbDevice> deviceList = usbManager.getDeviceList();
if (deviceList.size() <= 0)
{
Toast.makeText(getApplicationContext(), "Info: No device found", Toast.LENGTH_SHORT).show();
}
else
{
Toast.makeText(getApplicationContext(), "No of devices"+deviceList.size(), Toast.LENGTH_SHORT).show();
((TextView) findViewById(R.id.textView_devices))
.setText("No of device : " + deviceList.size());
}
Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();
int count = 0;
mPermissionIntent = PendingIntent.getBroadcast(getBaseContext(), 0,
new Intent(ACTION_USB_PERMISSION), 0);
while (deviceIterator.hasNext()) {
count++;
device = deviceIterator.next();
Log.i("info", "Device No " + count + "........");
Log.i("info", "Vendor id : " + device.getVendorId());
Log.i("info", "Product id : " + device.getProductId());
Log.i("info", "Device name : " + device.getDeviceName());
Log.i("info", "Device class : " + device.getClass().getName());
Log.i("info", "Device protocol: " + device.getDeviceProtocol());
Log.i("info", "Device subclass : " + device.getDeviceSubclass());
if (device.getVendorId() == PRINTER_VENDOR_ID) {
printer = device;
break;
}
}
findViewById(R.id.button_print).setOnClickListener(
new OnClickListener() {
@Override
public void onClick(View v) {
Log.i("Info", "Print command given");
IntentFilter filter = new IntentFilter(
ACTION_USB_PERMISSION);
registerReceiver(mUsbReceiver, filter);
if (printer != null) {
usbManager.requestPermission(printer,
mPermissionIntent);
} else {
Log.e("Exception", "Printer not found");
}
}
});
} catch (Exception e) {
Log.e("Exception", "Exception in onCreate " + e.getMessage());
e.printStackTrace();
}
findViewById(R.id.button_create_file).setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View v)
{
try
{
FileOutputStream fos = new FileOutputStream(myInternalFile+"\n");
fos.write(data.toString().getBytes());
fos.close();
}
catch (IOException e)
{
e.printStackTrace();
}
}
});
}
private final BroadcastReceiver mUsbReceiver = new BroadcastReceiver()
{
@Override
public void onReceive(Context context, Intent intent)
{
try {
String action = intent.getAction();
if (ACTION_USB_PERMISSION.equals(action))
{
synchronized (this)
{
final UsbDevice printerDevice = (UsbDevice) intent
.getParcelableExtra(UsbManager.EXTRA_DEVICE);
if (intent.getBooleanExtra(
UsbManager.EXTRA_PERMISSION_GRANTED, false))
{
if (printerDevice != null) {
Log.i("Info", "Device permission granted");
startPrinting(printerDevice);
}
}
else
{
Log.d("Debug", "permission denied for device "
+ printerDevice);
}
}
}
} catch (Exception e)
{
Log.e("Exception", "Exception in onRecieve " + e.getMessage());
e.printStackTrace();
}
}
};
public void startPrinting(final UsbDevice printerDevice)
{
new Handler().post(new Runnable()
{
UsbDeviceConnection conn;
UsbInterface usbInterface;
@Override
public void run()
{
try
{
Log.i("Info", "Bulk transfer started");
usbInterface = printerDevice.getInterface(0);
UsbEndpoint endPoint = usbInterface.getEndpoint(0);
conn = usbManager.openDevice(printer);
conn.claimInterface(usbInterface, true);
String myStringData = print_text.getText().toString();
myStringData+="\n";
byte[] array = myStringData.getBytes();
ByteBuffer output_buffer = ByteBuffer
.allocate(array.length);
UsbRequest request = new UsbRequest();
request.initialize(conn, endPoint);
request.queue(output_buffer, array.length);
if (conn.requestWait() == request)
{
Log.i("Info", output_buffer.getChar(0) + "");
Message m = new Message();
m.obj = output_buffer.array();
// handler.sendMessage(m);
output_buffer.clear();
}
else
{
Log.i("Info", "No request recieved");
}
int transfered = conn.bulkTransfer(endPoint,
myStringData.getBytes(),
myStringData.getBytes().length, 5000);
Log.i("Info", "Amount of data transferred : " +transfered);
} catch (Exception e)
{
Log.e("Exception", "Unable to transfer bulk data");
e.printStackTrace();
} finally
{
try
{
conn.releaseInterface(usbInterface);
Log.i("Info", "Interface released");
conn.close();
Log.i("Info", "Usb connection closed");
unregisterReceiver(mUsbReceiver);
Log.i("Info", "Brodcast reciever unregistered");
}
catch (Exception e)
{
Log.e("Exception",
"Unable to release resources because : "
+ e.getMessage());
e.printStackTrace();
}
}
}
});
}
}