I currently have a bluetooth service wherein there is a thread that manages the bluetooth connection after it has been established. When i check if the thread is alive with isAlive, then i get true if i remain in the same activity that establishes the connection. But, if i call the same function from a different activity to check if it is alive, then i get the following error:

java.lang.NullPointerException: Attempt to invoke virtual method ‘boolean com.example.bluetooth.BTservice$ConnectedThread.isAlive()’ on a null object reference

this is the thread in question:

public class ConnectedThread extends Thread {
        private final BluetoothSocket mmSocket;
        private final InputStream mmInStream;
        private final OutputStream mmOutStream;

        public ConnectedThread(BluetoothSocket socket) {
            Log.d(TAG, "ConnectedThread: Starting.");

            mmSocket = socket;
            InputStream tmpIn = null;
            OutputStream tmpOut = null;

            //dismiss the progressdialog when connection is established
            try{
                mProgressDialog.dismiss();
            }catch (NullPointerException e){
                System.out.println("Null pointer exception");
                e.printStackTrace();
            }


            try {
                tmpIn = mmSocket.getInputStream();
                tmpOut = mmSocket.getOutputStream();
            } catch (IOException e) {
                e.printStackTrace();
            }

            mmInStream = tmpIn;
            mmOutStream = tmpOut;
        }

        public void run(){
            byte[] buffer = new byte[1024];  // buffer store for the stream

            int bytes; // bytes returned from read()

            // Keep listening to the InputStream until an exception occurs
            while (true) {
                // Read from the InputStream
                try {
                    bytes = mmInStream.read(buffer);
                    String incomingMessage = new String(buffer, 0, bytes);
                    Log.d(TAG, "InputStream: " + incomingMessage);
                    Intent incomingMessageIntent = new Intent("incomingMessage");
                    incomingMessageIntent.putExtra("incomingMessage", incomingMessage);

                } catch (IOException e) {
                    Log.e(TAG, "write: Error reading Input Stream. " + e.getMessage() );
                    break;
                }
            }
        }

        //Call this from the main activity to send data to the remote device
        public void write(byte[] bytes) {
            String text = new String(bytes, Charset.defaultCharset());
            Log.d(TAG, "write: Writing to outputstream: " + text);
            try {
                mmOutStream.write(bytes);
            } catch (IOException e) {
                Log.e(TAG, "write: Error writing to output stream. " + e.getMessage() );
            }
        }

        /* Call this from the main activity to shutdown the connection */
        public void cancel() {
            try {
                mmSocket.close();
                System.out.println("Closing socket");
            } catch (IOException e) { }
        }
    }

The function that i am calling is also in the service class

public void checkAliveStatus(){ System.out.println("is connected thread alive"+mConnectedThread.isAlive()); }

I have tried to create another activity to see if the issue was that i returned to the main activity but the same error occurs.