Print from another activity - android-studio

Question

I managed to establish a bluetooth connection from my main activity but i want to print from another activity.
How can I do this?
Main Activity Where I Start A connection to a bluetooth printer
protected static final String TAG = "TAG";
private static final int REQUEST_ENABLE_BT = 2;
private static final int REQUEST_CONNECT_DEVICE = 1;
private ProgressDialog BluetoothConnectProgressDialog;
Button button_connect_to_bluetooth_printer;
private UUID applicationUUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
private BluetoothAdapter bluetoothAdapter;
private BluetoothSocket bluetoothSocket;
private BluetoothDevice bluetoothDevice;
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button_connect_to_bluetooth_printer = findViewById(R.id.btn_connect_bluetooth);
button_connect_to_bluetooth_printer.setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View view)
{
bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
if (!bluetoothAdapter.isEnabled())
{
Intent enableBluetooth = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBluetooth, REQUEST_ENABLE_BT);
}
else
{
ListPairedDevices();
Intent connectIntent = new Intent(MainActivity.this, BluetoothDeviceListActivity.class);
startActivityForResult(connectIntent,
REQUEST_CONNECT_DEVICE);
}
}
});
}
private void ListPairedDevices()
{
Set<BluetoothDevice> PairedDevices = bluetoothAdapter.getBondedDevices();
if (PairedDevices.size() > 0)
{
for (BluetoothDevice mDevice : PairedDevices)
{
Log.v(TAG, "PairedDevices: " + mDevice.getName() + mDevice.getAddress());
}
}
}
public void onActivityResult(int RequestCode, int ResultCode, Intent DataIntent)
{
super.onActivityResult(RequestCode, ResultCode, DataIntent);
switch (RequestCode)
{
case REQUEST_CONNECT_DEVICE:
if (ResultCode == Activity.RESULT_OK)
{
Bundle mExtra = DataIntent.getExtras();
String mDeviceAddress = mExtra.getString("DeviceAddress");
Log.v(TAG, "Coming incoming address " + mDeviceAddress);
bluetoothDevice = bluetoothAdapter
.getRemoteDevice(mDeviceAddress);
BluetoothConnectProgressDialog = ProgressDialog.show(this, "Connecting...", bluetoothDevice.getName() + " : " + bluetoothDevice.getAddress(), true, true);
Thread mBlutoothConnectThread = new Thread(this);
mBlutoothConnectThread.start();
// pairToDevice(mBluetoothDevice); This method is replaced by
// progress dialog with thread
}
break;
case REQUEST_ENABLE_BT:
if (ResultCode == Activity.RESULT_OK) {
ListPairedDevices();
Intent connectIntent = new Intent(MainActivity.this,
BluetoothDeviceListActivity.class);
startActivityForResult(connectIntent, REQUEST_CONNECT_DEVICE);
} else {
Toast.makeText(MainActivity.this, "Message", Toast.LENGTH_SHORT).show();
}
break;
}
}
public void run()
{
try
{
bluetoothSocket = bluetoothDevice.createRfcommSocketToServiceRecord(applicationUUID);
bluetoothAdapter.cancelDiscovery();
bluetoothSocket.connect();
handler.sendEmptyMessage(0);
}
catch (IOException eConnectException)
{
Log.d(TAG, "CouldNotConnectToSocket", eConnectException);
closeSocket(bluetoothSocket);
return;
}
}
#SuppressLint("HandlerLeak")
private Handler handler = new Handler() {
#Override
public void handleMessage(Message msg)
{
BluetoothConnectProgressDialog.dismiss();
}
};
private void closeSocket(BluetoothSocket nOpenSocket)
{
try
{
nOpenSocket.close();
Log.d(TAG, "SocketClosed");
}
catch (IOException ex)
{
Log.d(TAG, "CouldNotCloseSocket");
}
}
this is my device list activity
protected static final String TAG = "TAG";
private BluetoothAdapter bluetoothAdapter;
private ArrayAdapter<String> paired_devices_list;
#Override
protected void onCreate(Bundle mSavedInstanceState)
{
super.onCreate(mSavedInstanceState);
requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
setContentView(R.layout.activity_bluetooth_device_list);
setResult(Activity.RESULT_CANCELED);
paired_devices_list = new ArrayAdapter<>(this, R.layout.bluetooth_device_name);
ListView PairedListDevices = findViewById(R.id.paired_devices);
PairedListDevices.setAdapter(paired_devices_list);
PairedListDevices.setOnItemClickListener(new AdapterView.OnItemClickListener()
{
#Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l)
{
try
{
bluetoothAdapter.cancelDiscovery();
String mdeviceInfo = ((TextView) view).getText().toString();
String deviceAddress = mdeviceInfo.substring(mdeviceInfo.length() - 17);
Log.v(TAG, "Device_Address " + deviceAddress);
Bundle bundle = new Bundle();
bundle.putString("DeviceAddress", deviceAddress);
Intent mBackIntent = new Intent();
mBackIntent.putExtras(bundle);
setResult(Activity.RESULT_OK, mBackIntent);
finish();
}
catch (Exception ex)
{
ex.printStackTrace();
}
}
});
bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
Set<BluetoothDevice> PairedDevices = bluetoothAdapter.getBondedDevices();
if (PairedDevices.size() > 0)
{
findViewById(R.id.title_paired_devices).setVisibility(View.VISIBLE);
for (BluetoothDevice mDevice : PairedDevices)
{
paired_devices_list.add(mDevice.getName() + "\n" + mDevice.getAddress());
}
}
else
{
String NoDevices = "None Paired";
paired_devices_list.add(NoDevices);
}
}
#Override
protected void onDestroy()
{
super.onDestroy();
if (bluetoothAdapter != null)
{
bluetoothAdapter.cancelDiscovery();
}
}
And this my print activity
public void print()
{
Thread t = new Thread()
{
public void run()
{
try
{
OutputStream os = bluetoothSocket.getOutputStream();
String account_no;
account_no_value = ""+ Account_No.getText().toString()+"\n";
os.write(account_no.getBytes());
}
catch (Exception e)
{
Log.e("PrintActivity", "Exe ", e);
}
}
};
t.start();
}
E/PrintActivity: Exe
java.lang.NullPointerException: Attempt to invoke virtual method 'java.io.OutputStream android.bluetooth.BluetoothSocket.getOutputStream()' on a null object reference
at com.vicjames.qiimeterreader.PrintBill$6.run(PrintBill.java:1635)
how can I fix this?? The app is not crashing but it wont print either.