Not able to pass Bluetooth Device address to create a socket in android

Question

I am working on an android app where I need to send text over Bluetooth. I have come up with a piece of code to achieve this. My problem is that I am not able to pass the address of the another device for creating the socket. the app crashes every time it reaches to the point : BluetoothDevice device = bluetooth.getRemoteDevice(address); where address is the mac address of the device I want to connect to. My full code is:

package com.example.blueremote;

public class MainActivity extends Activity {
    private BluetoothAdapter bluetooth;
    private BluetoothSocket socket;
    private Button btnSend;
    private ArrayList<BluetoothDevice> foundDevices;
    private ArrayAdapter<BluetoothDevice> aa;
    private Handler handler = new Handler();

    private ListView list;
    private TextView tvmsg;
    private static int DISCOVERY_REQUEST = 1;
    private UUID uuid = UUID.fromString("a60f35f0-b93a-11de-8a39-08002009c666");
    ImageButton up;
    private String address = "D8:50:E6:8A:16:0F";

    private String text = "up";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Intent disc;
        disc = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
        startActivityForResult(disc, DISCOVERY_REQUEST);
        up = (ImageButton) findViewById(R.id.btn_up);

        registerReceiver(discoveryResult, new IntentFilter(
                BluetoothDevice.ACTION_FOUND));
        up.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                Log.v("Main Activity", "In up Button");
                // Log.v("Main Activity", "Invoking switchUI");

                AsyncTask<Integer, Void, Void> connectTask = new AsyncTask<Integer, Void, Void>() {

                    @Override
                    protected Void doInBackground(Integer... params) {
                        // TODO Auto-generated method stub
                        try {
                            Log.v("Main Activity", " AsyncTask started");
                            BluetoothDevice device = bluetooth
                                    .getRemoteDevice(address);

                            socket = device
                                    .createRfcommSocketToServiceRecord(uuid);
                            Log.v("Main Activity", "Socket Created");
                            socket.connect();

                            Log.v("Main Activity", "Socket Connected");
                        } catch (IOException e) {
                            Log.d("BLUETOOTH_CLIENT", e.getMessage());
                        }
                        return null;
                    }

                    @Override
                    protected void onPostExecute(Void result) {
                        // Log.v("Main Activity", "Invoking switchUI");
                        switchUI();

                    }
                };
                connectTask.execute();

            }
        });
    }

    private void switchUI() {
        Log.v("Main Activity", "In SwitchUI Method");

        Log.v("Main Activity", "Invoking sendMessage Method ");
        sendMessage(socket, text);
        Log.v("Main Activity", "Message Sent");

        BluetoothSocketListener bsl = new BluetoothSocketListener(socket,
                handler);
        Thread messageListener = new Thread(bsl);
        messageListener.start();
    }

    private void sendMessage(BluetoothSocket socket, String msg) {
        msg = "hi";
        OutputStream outStream;
        try {
            Log.v("Main Activity", "Inside sendMessage Method ");

            outStream = socket.getOutputStream();
            Log.v("Main Activity", "Outstream:" + outStream);
            byte[] byteString = (msg + " ").getBytes();
            Log.v("Main Activity", "byteString:" + byteString);

            outStream.write(byteString);
            Log.v("Main Activity", "outstream written:");
        } catch (IOException e) {
            Log.d("BLUETOOTH_COMMS", e.getMessage());
        }
    }

    private class MessagePoster implements Runnable {
        private TextView textView;
        private String message;

        public MessagePoster(TextView textView, String message) {
            this.textView = textView;
            this.message = message;
        }

        public void run() {
            textView.setText(message);
        }
    }

    private class BluetoothSocketListener implements Runnable {
        private BluetoothSocket socket;
        private TextView textView;
        private Handler handler;

        public BluetoothSocketListener(BluetoothSocket socket, Handler handler) {
            this.socket = socket;
            // this.textView = textView;
            this.handler = handler;
        }

        public void run() {
            int bufferSize = 2048;
            byte[] buffer = new byte[bufferSize];
            try {
                InputStream instream = socket.getInputStream();
                int bytesRead = -1;
                String message = "";
                while (true) {
                    message = "hello";
                    bytesRead = instream.read(buffer);
                    if (bytesRead != -1) {
                        while ((bytesRead == bufferSize)
                                && (buffer[bufferSize - 1] != 0)) {
                            message = message
                                    + new String(buffer, 0, bytesRead);
                            bytesRead = instream.read(buffer);
                        }
                        message = message
                                + new String(buffer, 0, bytesRead - 1);
                        handler.post(new MessagePoster(textView, message));
                        socket.getInputStream();
                    }
                }
            } catch (IOException e) {
                Log.d("BLUETOOTH_COMMS", e.getMessage());
            }
        }
    }

    /*
     * protected void onActivityResult(int requestCode, int resultCode, Intent
     * data) { if (requestCode == DISCOVERY_REQUEST) { boolean isDiscoverable =
     * resultCode > 0; if (isDiscoverable) { String name = "bluetoothserver";
     * try { final BluetoothServerSocket btserver = bluetooth
     * .listenUsingRfcommWithServiceRecord(name, uuid); AsyncTask<Integer, Void,
     * BluetoothSocket> acceptThread = new AsyncTask<Integer, Void,
     * BluetoothSocket>() {
     * 
     * @Override protected void onPostExecute(BluetoothSocket result) { if
     * (result != null) switchUI(); }
     * 
     * @Override protected BluetoothSocket doInBackground( Integer... params) {
     * // TODO Auto-generated method stub try { socket =
     * btserver.accept(params[0] * 1000); return socket; } catch (IOException e)
     * { Log.d("BLUETOOTH", e.getMessage()); } return null; } };
     * acceptThread.execute(resultCode); } catch (IOException e) {
     * Log.d("BLUETOOTH", e.getMessage()); } } } }
     */

    BroadcastReceiver discoveryResult = new BroadcastReceiver() {

        @Override
        public void onReceive(Context context, Intent intent) {
            // TODO Auto-generated method stub
            BluetoothDevice remoteDevice;
            remoteDevice = intent
                    .getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
            if (bluetooth.getBondedDevices().contains(remoteDevice)) {
                foundDevices.add(remoteDevice);
                aa.notifyDataSetChanged();
            }
        }
    };

    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(discoveryResult);
    }

}

This is what my logcat has to say:

E/AndroidRuntime( 5421): FATAL EXCEPTION: AsyncTask #1

E/AndroidRuntime( 5421): java.lang.RuntimeException: An error occured while executing doInBackground()

E/AndroidRuntime( 5421):    at android.os.AsyncTask$3.done(AsyncTask.java:299)

E/AndroidRuntime( 5421):    at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)

E/AndroidRuntime( 5421):    at java.util.concurrent.FutureTask.setException(FutureTask.java:219)

E/AndroidRuntime( 5421):    at java.util.concurrent.FutureTask.run(FutureTask.java:239)

E/AndroidRuntime( 5421):    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)

E/AndroidRuntime( 5421):    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)

E/AndroidRuntime( 5421):    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)

E/AndroidRuntime( 5421):    at java.lang.Thread.run(Thread.java:838)

E/AndroidRuntime( 5421): Caused by: java.lang.NullPointerException

E/AndroidRuntime( 5421):    at com.example.blueremote.MainActivity$2$1.doInBackground(MainActivity.java:75)

E/AndroidRuntime( 5421):    at com.example.blueremote.MainActivity$2$1.doInBackground(MainActivity.java:1)

E/AndroidRuntime( 5421):    at android.os.AsyncTask$2.call(AsyncTask.java:287)

E/AndroidRuntime( 5421):    at java.util.concurrent.FutureTask.run(FutureTask.java:234)

Any idea how can I create a socket would be really appreciated. Thanks in advance

Answer 1

Caused by: java.lang.NullPointerException

at com.example.blueremote.MainActivity$2$1.doInBackground(MainActivity.java:75)

which indicates line

BluetoothDevice device = bluetooth.getRemoteDevice(address);

Problem

bluetooth isn't initialized.