mBluetoothSocket.connect() prints a line

Question

I have been trying to find a solution for this, but not able to. So I am developing an POS app in Android and I need to print receipts for sales/purchase using a bluetooth printer.

The printing, is working fine, per se, but whenever I call mBluetoothSocket.connect(), it prints out CONNECT "8869-XX-XXXXXX" on top of the print, which I don't want. I do not want to leave the connection open for long and I want the app to connect only when needed. How to achieve this? Any help guys. Find the code below.0 Thanks in advance.

package anil.com.andoirdbluetoothprint;


import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.util.Set;
import java.util.UUID;

import android.app.Activity;
import android.app.ProgressDialog;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.view.Window;
import android.view.WindowManager;
import android.widget.Button;
import android.widget.Toast;


public class MainActivity extends Activity implements Runnable {
    protected static final String TAG = "TAG";
    private static final int REQUEST_CONNECT_DEVICE = 1;
    private static final int REQUEST_ENABLE_BT = 2;
    Button mScan, mPrint, mDisc;
    BluetoothAdapter mBluetoothAdapter;
    private UUID applicationUUID = UUID
            .fromString("00001101-0000-1000-8000-00805F9B34FB");
    private ProgressDialog mBluetoothConnectProgressDialog;
    private BluetoothSocket mBluetoothSocket;
    BluetoothDevice mBluetoothDevice;

    @Override
    public void onCreate(Bundle mSavedInstanceState) {
        super.onCreate(mSavedInstanceState);
        setContentView(R.layout.activity_main);
        mScan = (Button) findViewById(R.id.Scan);
        mScan.setOnClickListener(new View.OnClickListener() {
            public void onClick(View mView) {
                mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
                if (mBluetoothAdapter == null) {
                    Toast.makeText(MainActivity.this, "Message1", Toast.LENGTH_SHORT).show();
                } else {
                    if (!mBluetoothAdapter.isEnabled()) {
                        Intent enableBtIntent = new Intent(
                                BluetoothAdapter.ACTION_REQUEST_ENABLE);
                        startActivityForResult(enableBtIntent,
                                REQUEST_ENABLE_BT);
                    } else {
                        ListPairedDevices();
                        Intent connectIntent = new Intent(MainActivity.this,
                                DeviceListActivity.class);
                        startActivityForResult(connectIntent,
                                REQUEST_CONNECT_DEVICE);
                    }
                }
            }
        });

        mPrint = (Button) findViewById(R.id.mPrint);
        mPrint.setOnClickListener(new View.OnClickListener() {
            public void onClick(View mView) {
                Thread t = new Thread() {
                    public void run() {
                        try {
                            OutputStream os = mBluetoothSocket
                                    .getOutputStream();
                            String BILL = "";
// Before this line, it is printing "CONNECT 88C9-XX-XXXXXX"
                            BILL = "Company Name    \n";
                            BILL = BILL + "Address    \n";
                            BILL = BILL + "---------------    \n";
                            BILL = BILL + "Item1 : Quantity    \n";
                            BILL = BILL + "Rate : 100 $    \n";
                            BILL = BILL + "-----------------\n";
                            BILL = BILL + "Thank You    \n";
                            os.write(BILL.getBytes());
                            //This is printer specific code you can comment ==== > Start

                            // Setting height
                            int gs = 29;
                            os.write(intToByteArray(gs));
                            int h = 104;
                            os.write(intToByteArray(h));
                            int n = 162;
                            os.write(intToByteArray(n));

                            // Setting Width
                            int gs_width = 29;
                            os.write(intToByteArray(gs_width));
                            int w = 119;
                            os.write(intToByteArray(w));
                            int n_width = 2;
                            os.write(intToByteArray(n_width));


                        } catch (Exception e) {
                            Log.e("MainActivity", "Exe ", e);
                        }
                    }
                };
                t.start();
            }
        });

        mDisc = (Button) findViewById(R.id.dis);
        mDisc.setOnClickListener(new View.OnClickListener() {
            public void onClick(View mView) {
                if (mBluetoothAdapter != null)
                    mBluetoothAdapter.disable();
            }
        });

    }// onCreate

    @Override
    protected void onDestroy() {
        // TODO Auto-generated method stub
        super.onDestroy();
        try {
            if (mBluetoothSocket != null)
                mBluetoothSocket.close();
        } catch (Exception e) {
            Log.e("Tag", "Exe ", e);
        }
    }

    @Override
    public void onBackPressed() {
        try {
            if (mBluetoothSocket != null)
                mBluetoothSocket.close();
        } catch (Exception e) {
            Log.e("Tag", "Exe ", e);
        }
        setResult(RESULT_CANCELED);
        finish();
    }

    public void onActivityResult(int mRequestCode, int mResultCode,
                                 Intent mDataIntent) {
        super.onActivityResult(mRequestCode, mResultCode, mDataIntent);

        switch (mRequestCode) {
            case REQUEST_CONNECT_DEVICE:
                if (mResultCode == Activity.RESULT_OK) {
                    Bundle mExtra = mDataIntent.getExtras();
                    String mDeviceAddress = mExtra.getString("DeviceAddress");
                    Log.v(TAG, "Coming incoming address " + mDeviceAddress);
                    mBluetoothDevice = mBluetoothAdapter
                            .getRemoteDevice(mDeviceAddress);
                    mBluetoothConnectProgressDialog = ProgressDialog.show(this,
                            "Connecting...", mBluetoothDevice.getName() + " : "
                                    + mBluetoothDevice.getAddress(), true, false);
                    Thread mBlutoothConnectThread = new Thread(this);
                    mBlutoothConnectThread.start();
                    // pairToDevice(mBluetoothDevice); This method is replaced by
                    // progress dialog with thread
                }
                break;

            case REQUEST_ENABLE_BT:
                if (mResultCode == Activity.RESULT_OK) {
                    ListPairedDevices();
                    Intent connectIntent = new Intent(MainActivity.this,
                            DeviceListActivity.class);
                    startActivityForResult(connectIntent, REQUEST_CONNECT_DEVICE);
                } else {
                    Toast.makeText(MainActivity.this, "Message", Toast.LENGTH_SHORT).show();
                }
                break;
        }
    }

    private void ListPairedDevices() {
        Set<BluetoothDevice> mPairedDevices = mBluetoothAdapter
                .getBondedDevices();
        if (mPairedDevices.size() > 0) {
            for (BluetoothDevice mDevice : mPairedDevices) {
                Log.v(TAG, "PairedDevices: " + mDevice.getName() + "  "
                        + mDevice.getAddress());
            }
        }
    }

    public void run() {
        try {
            mBluetoothSocket = mBluetoothDevice
                    .createRfcommSocketToServiceRecord(applicationUUID);
            mBluetoothAdapter.cancelDiscovery();
            mBluetoothSocket.connect();
            mHandler.sendEmptyMessage(0);
        } catch (IOException eConnectException) {
            Log.d(TAG, "CouldNotConnectToSocket", eConnectException);
            closeSocket(mBluetoothSocket);
            return;
        }
    }

    private void closeSocket(BluetoothSocket nOpenSocket) {
        try {
            nOpenSocket.close();
            Log.d(TAG, "SocketClosed");
        } catch (IOException ex) {
            Log.d(TAG, "CouldNotCloseSocket");
        }
    }

    private Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            mBluetoothConnectProgressDialog.dismiss();
            Toast.makeText(MainActivity.this, "DeviceConnected", Toast.LENGTH_SHORT).show();
        }
    };

    public static byte intToByteArray(int value) {
        byte[] b = ByteBuffer.allocate(4).putInt(value).array();

        for (int k = 0; k < b.length; k++) {
            System.out.println("Selva  [" + k + "] = " + "0x"
                    + UnicodeFormatter.byteToHex(b[k]));
        }

        return b[3];
    }

    public byte[] sel(int val) {
        ByteBuffer buffer = ByteBuffer.allocate(2);
        buffer.putInt(val);
        buffer.flip();
        return buffer.array();
    }

}

Answer 1

This is not Your code which is printing this line but the wrong printer configurations you have made . . . All printers have their on configurations and settings but almost majority of POS printers offer to configure page margin , HEADER(in your case) , footer and white spaces check this as printing prefrences so you are left with two choices

1 -> Either set preferences manually (it's convenient)

2 -> configure/set preferences before printing (You should have knowledge of printer commands for this to send to printer before actual data sending)

Last but not least it is also possible that your POS printer and Android device are not friendly together :D . . it is possible due to miss matched communication encoding your printer interprating the successfull shake hand code/response into printable data

You have to either disable it or send the code/response which your printer likes . .