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Create a listener, pass value from a BroadcastReceiver

I'm with some doubt how I can execute one action.
When receive one income call, I want to pass the number for my class it manager the Bluetooth connection with Arduino.
After send the number, I'd like to send it by bluetooth connection
I tried use intent but maybe I am using deprecated version.
Android Api 7.1
Brodcaster Receiver Class
package com.jidea.glass;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.telephony.TelephonyManager;
import android.util.Log;
import android.widget.Toast;
public class TelephonyReceiver extends BroadcastReceiver
{
#Override
public void onReceive(Context arg0, Intent intent) {
// TODO Auto-generated method stub
try {
if (intent != null && intent.getAction().equals("android.intent.action.NEW_OUTGOING_CALL")) {
//Toast.makeText(context, "Outgoign call", 1000).show();
String number = intent.getStringExtra(Intent.EXTRA_PHONE_NUMBER);
} else {
//get the phone state
String newPhoneState = intent.hasExtra(TelephonyManager.EXTRA_STATE) ? intent.getStringExtra(TelephonyManager.EXTRA_STATE) : null;
Bundle bundle = intent.getExtras();
if (newPhoneState != null && newPhoneState.equals(TelephonyManager.EXTRA_STATE_RINGING)) {
//read the incoming call number
String phoneNumber = bundle.getString(TelephonyManager.EXTRA_INCOMING_NUMBER);
Log.i("PHONE RECEIVER", "Telephone is now ringing " + phoneNumber);
//Toast.makeText(arg0, "Tele disponivel " + phoneNumber, Toast.LENGTH_LONG).show();
if(phoneNumber!=null | phoneNumber.equals("")){
PASS HERE TO BLUETOOTH
}
}
Bluetooth class
package com.jidea.glass;
import android.app.ProgressDialog;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
//import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;
import java.io.IOException;
import java.util.UUID;
public class CustomProcess extends AppCompatActivity
{
String address = null;
private ProgressDialog progress;
BluetoothAdapter myBluetooth = null;
BluetoothSocket btSocket = null;
private boolean isBtConnected = false;
//SPP UUID. Look for it
static final UUID myUUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
//observable
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Intent newint = getIntent();
address = newint.getStringExtra(MainActivity.EXTRA_ADDRESS); //receive the address of the bluetooth device
setContentView(R.layout.activity_custom_process);
//msg(address);
new ConnectBT().execute(); //Call the class to connect
}
public void isConnected() {//View view
if (btSocket!=null)
{
try
{
btSocket.getOutputStream().write("Conectado".toString().getBytes());
}
catch (IOException e)
{
msg("Error");
}
}
}
public void haveCall(String Phone) {//View view
Object aLig="Ligação \n"+Phone;
if (btSocket!=null)
{
try
{
btSocket.getOutputStream().write(aLig.toString().getBytes());
}
catch (IOException e)
{
msg("Error");
}
}
}
private void msg(String s)
{
Toast.makeText(getApplicationContext(),s,Toast.LENGTH_LONG).show();
}
private class ConnectBT extends AsyncTask<Void, Void, Void> // UI thread
{
private boolean ConnectSuccess = true; //if it's here, it's almost connected
#Override
protected void onPreExecute()
{
progress = ProgressDialog.show(CustomProcess.this, "Connecting...", "Please wait!!!"); //show a progress dialog
}
#Override
protected Void doInBackground(Void... devices) //while the progress dialog is shown, the connection is done in background
{
try
{
if (btSocket == null || !isBtConnected)
{
myBluetooth = BluetoothAdapter.getDefaultAdapter();//get the mobile bluetooth device
BluetoothDevice dispositivo = myBluetooth.getRemoteDevice(address);//connects to the device's address and checks if it's available
btSocket = dispositivo.createInsecureRfcommSocketToServiceRecord(myUUID);//create a RFCOMM (SPP) connection
BluetoothAdapter.getDefaultAdapter().cancelDiscovery();
btSocket.connect();//start connection
}
}
catch (IOException e)
{
ConnectSuccess = false;//if the try failed, you can check the exception here
}
return null;
}
#Override
protected void onPostExecute(Void result) //after the doInBackground, it checks if everything went fine
{
super.onPostExecute(result);
if (!ConnectSuccess)
{
msg("Connection Failed. Is it a SPP Bluetooth? Try again.");
finish();
}
else
{
msg("Conectado");
isBtConnected = true;
isConnected();
}
progress.dismiss();
}
}
}

First you should create an intent in your BroadcastReceiver and then use LocalBroadcastManager in order to be able to send that intent wherever you want to listen.
val intent = Intent(ACTION)
intent.putExtra("DATA KEY", DATA)
LocalBroadcastManager.getInstance(context).sendBroadcast(intent)
don't forget to register your broadcast receiver in where you want to listen
LocalBroadcastManager.getInstance(context).registerReceiver(your broadcast receiver instance, IntentFilter(ACTION))

I solved it done a Java Internal Listener with Interface the codes.
package com.jidea.glass;
public interface TelephonyListener
{
/**
* To call this method when new message received and send back
* #param message Message
*/
void callReceived(String message);
}
public class CustomProcess extends AppCompatActivity implements MessageListener, TelephonyListener
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
MessageReceiver.bindListener(this);
TelephonyReceiver.bindListener(this);
Intent newint = getIntent();
address = newint.getStringExtra(MainActivity.EXTRA_ADDRESS); //receive the address of the bluetooth device
setContentView(R.layout.activity_custom_process);
//msg(address);
new ConnectBT().execute(); //Call the class to connect
#Override
public void messageReceived(String message)
{
Toast.makeText(this, "Nova Mensagem: " + message, Toast.LENGTH_SHORT).show();
}
#Override
public void callReceived(String message) {
Toast.makeText(this , "Tele disponivel " + message, Toast.LENGTH_LONG).show();
haveCall(message);
}
Continues in my class Receiver it extends BroadcastReceiver I Donw
public class TelephonyReceiver extends BroadcastReceiver
{
private static TelephonyListener mListener;
#Override
public void onReceive(Context arg0, Intent intent) {
// TODO Auto-generated method stub
}
public static void bindListener(TelephonyListener listener){
mListener = listener;
}

Making a bluetooth service that sends a signal to arduino bluetooth module

So I have been working with arduino for a while and now I've been trying to connect to the blue-tooth module with android studio. I was able to get the blue-tooth to connect but I'm having issues making the blue-tooth connection a service so that it can run even if the app is closed. Whenever I try to get the service to run on my phone, the app crashes as soon as i try to connect to blue-tooth module where as before when it was an activity, it worked perfectly. I've looked at a lot of links and guides on using services and blue-tooth but none of them do exactly what I want.
Below are some code snippets, but here is a link to the entire GitHub project
Blue-tooth activity that I got to work:
package edu.memphis.teamhack.smart_nightlight;
import android.Manifest;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.SharedPreferences;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.os.Handler;
import android.os.SystemClock;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.lang.reflect.Method;
import java.util.Set;
import java.util.UUID;
public class BluetoothActivity extends AppCompatActivity {
// GUI Components
private TextView mBluetoothStatus;
private TextView mReadBuffer;
private Button mScanBtn;
private Button mOffBtn;
private Button mListPairedDevicesBtn;
private Button mDiscoverBtn;
private BluetoothAdapter mBTAdapter;
private Set<BluetoothDevice> mPairedDevices;
private ArrayAdapter<String> mBTArrayAdapter;
private ListView mDevicesListView;
private CheckBox mLED1;
private final String TAG = MainActivity.class.getSimpleName();
private Handler mHandler; // Our main handler that will receive callback notifications
private ConnectedThread mConnectedThread; // bluetooth background worker thread to send and receive data
private BluetoothSocket mBTSocket = null; // bi-directional client-to-client data path
private static final UUID BTMODULEUUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB"); // "random" unique identifier
// #defines for identifying shared types between calling functions
private final static int REQUEST_ENABLE_BT = 1; // used to identify adding bluetooth names
private final static int MESSAGE_READ = 2; // used in bluetooth handler to identify message update
private final static int CONNECTING_STATUS = 3; // used in bluetooth handler to identify message status
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_bluetooth);
mBluetoothStatus = (TextView)findViewById(R.id.bluetoothStatus);
mReadBuffer = (TextView) findViewById(R.id.readBuffer);
mScanBtn = (Button)findViewById(R.id.scan);
mOffBtn = (Button)findViewById(R.id.off);
mDiscoverBtn = (Button)findViewById(R.id.discover);
mListPairedDevicesBtn = (Button)findViewById(R.id.PairedBtn);
mLED1 = (CheckBox)findViewById(R.id.checkboxLED1);
mBTArrayAdapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1);
mBTAdapter = BluetoothAdapter.getDefaultAdapter(); // get a handle on the bluetooth radio
mDevicesListView = (ListView)findViewById(R.id.devicesListView);
mDevicesListView.setAdapter(mBTArrayAdapter); // assign model to view
mDevicesListView.setOnItemClickListener(mDeviceClickListener);
// Ask for location permission if not already allowed
if(ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED)
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_COARSE_LOCATION}, 1);
mHandler = new Handler(){
public void handleMessage(android.os.Message msg){
if(msg.what == MESSAGE_READ){
String readMessage = null;
try {
readMessage = new String((byte[]) msg.obj, "UTF-8");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
mReadBuffer.setText(readMessage);
}
if(msg.what == CONNECTING_STATUS){
if(msg.arg1 == 1)
mBluetoothStatus.setText("Connected to Device: " + (String)(msg.obj));
else
mBluetoothStatus.setText("Connection Failed");
}
}
};
if (mBTArrayAdapter == null) {
// Device does not support Bluetooth
mBluetoothStatus.setText("Status: Bluetooth not found");
Toast.makeText(getApplicationContext(),"Bluetooth device not found!",Toast.LENGTH_SHORT).show();
}
else {
mLED1.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View v){
SharedPreferences settings = getSharedPreferences("MyPref",
Context.MODE_PRIVATE);
Integer myInt = settings.getInt("colorHex", 0);
if(mConnectedThread != null){ //First check to make sure thread created
mConnectedThread.write(myInt.toString());}
}
});
mScanBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
bluetoothOn(v);
}
});
mOffBtn.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View v){
bluetoothOff(v);
}
});
mListPairedDevicesBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v){
listPairedDevices(v);
}
});
mDiscoverBtn.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View v){
discover(v);
}
});
}
}
private void bluetoothOn(View view){
if (!mBTAdapter.isEnabled()) {
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
mBluetoothStatus.setText("Bluetooth enabled");
Toast.makeText(getApplicationContext(),"Bluetooth turned on",Toast.LENGTH_SHORT).show();
}
else{
Toast.makeText(getApplicationContext(),"Bluetooth is already on", Toast.LENGTH_SHORT).show();
}
}
// Enter here after user selects "yes" or "no" to enabling radio
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent Data){
// Check which request we're responding to
if (requestCode == REQUEST_ENABLE_BT) {
// Make sure the request was successful
if (resultCode == RESULT_OK) {
// The user picked a contact.
// The Intent's data Uri identifies which contact was selected.
mBluetoothStatus.setText("Enabled");
}
else
mBluetoothStatus.setText("Disabled");
}
}
private void bluetoothOff(View view){
mBTAdapter.disable(); // turn off
mBluetoothStatus.setText("Bluetooth disabled");
Toast.makeText(getApplicationContext(),"Bluetooth turned Off", Toast.LENGTH_SHORT).show();
}
private void discover(View view){
// Check if the device is already discovering
if(mBTAdapter.isDiscovering()){
mBTAdapter.cancelDiscovery();
Toast.makeText(getApplicationContext(),"Discovery stopped",Toast.LENGTH_SHORT).show();
}
else{
if(mBTAdapter.isEnabled()) {
mBTArrayAdapter.clear(); // clear items
mBTAdapter.startDiscovery();
Toast.makeText(getApplicationContext(), "Discovery started", Toast.LENGTH_SHORT).show();
registerReceiver(blReceiver, new IntentFilter(BluetoothDevice.ACTION_FOUND));
}
else{
Toast.makeText(getApplicationContext(), "Bluetooth not on", Toast.LENGTH_SHORT).show();
}
}
}
final BroadcastReceiver blReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if(BluetoothDevice.ACTION_FOUND.equals(action)){
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
// add the name to the list
mBTArrayAdapter.add(device.getName() + "\n" + device.getAddress());
mBTArrayAdapter.notifyDataSetChanged();
}
}
};
private void listPairedDevices(View view){
mPairedDevices = mBTAdapter.getBondedDevices();
if(mBTAdapter.isEnabled()) {
// put it's one to the adapter
for (BluetoothDevice device : mPairedDevices)
mBTArrayAdapter.add(device.getName() + "\n" + device.getAddress());
Toast.makeText(getApplicationContext(), "Show Paired Devices", Toast.LENGTH_SHORT).show();
}
else
Toast.makeText(getApplicationContext(), "Bluetooth not on", Toast.LENGTH_SHORT).show();
}
private AdapterView.OnItemClickListener mDeviceClickListener = new AdapterView.OnItemClickListener() {
public void onItemClick(AdapterView<?> av, View v, int arg2, long arg3) {
if(!mBTAdapter.isEnabled()) {
Toast.makeText(getBaseContext(), "Bluetooth not on", Toast.LENGTH_SHORT).show();
return;
}
mBluetoothStatus.setText("Connecting...");
// Get the device MAC address, which is the last 17 chars in the View
String info = ((TextView) v).getText().toString();
final String address = info.substring(info.length() - 17);
final String name = info.substring(0,info.length() - 17);
// Spawn a new thread to avoid blocking the GUI one
new Thread()
{
public void run() {
boolean fail = false;
BluetoothDevice device = mBTAdapter.getRemoteDevice(address);
try {
mBTSocket = createBluetoothSocket(device);
} catch (IOException e) {
fail = true;
Toast.makeText(getBaseContext(), "Socket creation failed", Toast.LENGTH_SHORT).show();
}
// Establish the Bluetooth socket connection.
try {
mBTSocket.connect();
} catch (IOException e) {
try {
fail = true;
mBTSocket.close();
mHandler.obtainMessage(CONNECTING_STATUS, -1, -1)
.sendToTarget();
} catch (IOException e2) {
//insert code to deal with this
Toast.makeText(getBaseContext(), "Socket creation failed", Toast.LENGTH_SHORT).show();
}
}
if(fail == false) {
mConnectedThread = new ConnectedThread(mBTSocket);
mConnectedThread.start();
mHandler.obtainMessage(CONNECTING_STATUS, 1, -1, name)
.sendToTarget();
}
}
}.start();
}
};
private BluetoothSocket createBluetoothSocket(BluetoothDevice device) throws IOException {
try {
final Method m = device.getClass().getMethod("createInsecureRfcommSocketToServiceRecord", UUID.class);
return (BluetoothSocket) m.invoke(device, BTMODULEUUID);
} catch (Exception e) {
Log.e(TAG, "Could not create Insecure RFComm Connection",e);
}
return device.createRfcommSocketToServiceRecord(BTMODULEUUID);
}
private class ConnectedThread extends Thread {
private final BluetoothSocket mmSocket;
private final InputStream mmInStream;
private final OutputStream mmOutStream;
public ConnectedThread(BluetoothSocket socket) {
mmSocket = socket;
InputStream tmpIn = null;
OutputStream tmpOut = null;
// Get the input and output streams, using temp objects because
// member streams are final
try {
tmpIn = socket.getInputStream();
tmpOut = socket.getOutputStream();
} catch (IOException e) { }
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) {
try {
// Read from the InputStream
bytes = mmInStream.available();
if(bytes != 0) {
buffer = new byte[1024];
SystemClock.sleep(100); //pause and wait for rest of data. Adjust this depending on your sending speed.
bytes = mmInStream.available(); // how many bytes are ready to be read?
bytes = mmInStream.read(buffer, 0, bytes); // record how many bytes we actually read
mHandler.obtainMessage(MESSAGE_READ, bytes, -1, buffer)
.sendToTarget(); // Send the obtained bytes to the UI activity
}
} catch (IOException e) {
e.printStackTrace();
break;
}
}
}
/* Call this from the main activity to send data to the remote device */
public void write(String input) {
byte[] bytes = input.getBytes(); //converts entered String into bytes
try {
mmOutStream.write(bytes);
} catch (IOException e) { }
}
/* Call this from the main activity to shutdown the connection */
public void cancel() {
try {
mmSocket.close();
} catch (IOException e) { }
}
}
Here is the Bluetooth Service I'm working on:
package edu.memphis.teamhack.smart_nightlight;
import android.app.Service;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.os.IBinder;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Toast;
public class BluetoothCommService extends Service {
// #defines for identifying shared types between calling functions
private final static int REQUEST_ENABLE_BT = 1; // used to identify adding bluetooth names
private BluetoothAdapter mBTAdapter;
private ArrayAdapter<String> mBTArrayAdapter;
public BluetoothCommService() {
}
public void onCreate(Bundle savedInstanceState){
//super.onCreate(savedInstanceState);
mBTAdapter = BluetoothAdapter.getDefaultAdapter(); // get a handle on the bluetooth radio
mBTArrayAdapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1);
}
#Override
public IBinder onBind(Intent intent) {
// TODO: Return the communication channel to the service.
throw new UnsupportedOperationException("Not yet implemented");
}
void bluetoothOn(View view){
if (!mBTAdapter.isEnabled()) {
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
//startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
//GUI
//mBluetoothStatus.setText("Bluetooth enabled");
// Toast.makeText(getApplicationContext(),"Bluetooth turned on",Toast.LENGTH_SHORT).show();
}
else{
//Toast.makeText(getApplicationContext(),"Bluetooth is already on", Toast.LENGTH_SHORT).show();
}
}
private void bluetoothOff(View view){
mBTAdapter.disable(); // turn off
//GUI
//mBluetoothStatus.setText("Bluetooth disabled");
//Toast.makeText(getApplicationContext(),"Bluetooth turned Off", Toast.LENGTH_SHORT).show();
}
private void discover(View view){
// Check if the device is already discovering
if(mBTAdapter.isDiscovering()){
mBTAdapter.cancelDiscovery();
Toast.makeText(getApplicationContext(),"Discovery stopped",Toast.LENGTH_SHORT).show();
}
else{
if(mBTAdapter.isEnabled()) {
mBTArrayAdapter.clear(); // clear items
mBTAdapter.startDiscovery();
Toast.makeText(getApplicationContext(), "Discovery started", Toast.LENGTH_SHORT).show();
registerReceiver(blReceiver, new IntentFilter(BluetoothDevice.ACTION_FOUND));
}
else{
Toast.makeText(getApplicationContext(), "Bluetooth not on", Toast.LENGTH_SHORT).show();
}
}
}
final BroadcastReceiver blReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if(BluetoothDevice.ACTION_FOUND.equals(action)){
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
// add the name to the list
mBTArrayAdapter.add(device.getName() + "\n" + device.getAddress());
mBTArrayAdapter.notifyDataSetChanged();
}
}
};
}
Feel free to ask any questions.

Try this instructables, i did it by reffering to this tutorial
http://www.instructables.com/id/Android-Bluetooth-Control-LED-Part-2/
for more idea, also refer to
https://www.intorobotics.com/how-to-develop-simple-bluetooth-android-application-to-control-a-robot-remote/

My Bluetooth app crashes randomly with the error: Error receiving broadCast Intent

So i'm working on a Bluetooth app and it crashes randomly sometimes and I've yet to found a solution. Logcat complains at the line if (device.getName().equals(pairedDevices.get(a))) { but I don't understand what that has to do with the crash?
Any help is appreciated!
Logcat:
02-23 11:47:05.311 28011-28037/com.example.asabanov.powersupplytool E/Surface: getSlotFromBufferLocked: unknown buffer: 0xb91b9980
02-23 11:47:15.718 28011-28011/com.example.asabanov.powersupplytool E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.asabanov.powersupplytool, PID: 28011
java.lang.RuntimeException: Error receiving broadcast Intent { act=android.bluetooth.device.action.FOUND flg=0x10 (has extras) } in com.example.asabanov.powersupplytool.BluetoothActivity$2#4d08f04
at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:934)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:168)
at android.app.ActivityThread.main(ActivityThread.java:5845)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:797)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:687)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference
at com.example.asabanov.powersupplytool.BluetoothActivity$2.onReceive(BluetoothActivity.java:129)
at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:915)
at android.os.Handler.handleCallback(Handler.java:739) 
at android.os.Handler.dispatchMessage(Handler.java:95) 
at android.os.Looper.loop(Looper.java:168) 
at android.app.ActivityThread.main(ActivityThread.java:5845) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:797) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:687) 
BluetoothActivity:
package com.example.asabanov.powersupplytool;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.view.Window;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Set;
import java.util.UUID;
public class BluetoothActivity extends AppCompatActivity implements OnItemClickListener {
public static final UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
protected static final int SUCCESS_CONNECT = 0;
protected static final int MESSAGE_READ = 1;
ArrayAdapter<String> listAdapter;
ListView listView;
BluetoothAdapter btAdapter;
Set<BluetoothDevice> devicesArray;
ArrayList<String> pairedDevices;
ArrayList<BluetoothDevice> devices;
IntentFilter filter;
BroadcastReceiver receiver;
String tag = "debugging";
Handler mHandler = new Handler() {
#Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
switch (msg.what) {
case SUCCESS_CONNECT:
//do something
ConnectedThread connectedThread = new ConnectedThread((BluetoothSocket) msg.obj);
Toast.makeText(getApplicationContext(), "Connect", Toast.LENGTH_SHORT).show();
String s = "Successfully connected";
connectedThread.write(s.getBytes());
break;
case MESSAGE_READ:
byte[] readBuf = (byte[]) msg.obj;
String string = new String(readBuf);
Toast.makeText(getApplicationContext(), "Connect", Toast.LENGTH_SHORT).show();
break;
}
}
};
#Override
public void onCreate(Bundle savedInstanceState) {
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_bluetooth);
init(); //initiate Bluetooth
if (btAdapter == null) {
Toast.makeText(getApplicationContext(), "No bluetooth detected on this device", Toast.LENGTH_SHORT).show();
finish();
} else {
if (!btAdapter.isEnabled()) {
turnOnBT();
}
pairedDevices=getPairedDevices();
startDiscovery();
}
}
private void startDiscovery() {
btAdapter.cancelDiscovery();
btAdapter.startDiscovery();
}
private void turnOnBT() {
Intent intent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(intent, 1);
}
private ArrayList getPairedDevices() {
devicesArray = btAdapter.getBondedDevices();
if (devicesArray.size() > 0) {
//add devices in array to list array
for (BluetoothDevice device : devicesArray) {
pairedDevices.add(device.getName() + "\n" + device.getAddress());
}
}
return pairedDevices;
}
private void init() {
listView = (ListView) findViewById(R.id.listView);
listView.setOnItemClickListener(this);
listAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, 0);
listView.setAdapter(listAdapter);
btAdapter = BluetoothAdapter.getDefaultAdapter();
pairedDevices = new ArrayList<String>();
filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
devices = new ArrayList<BluetoothDevice>();
receiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (BluetoothDevice.ACTION_FOUND.equals(action)) {
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
devices.add(device);
String s = "";
for (int a = 0; a < pairedDevices.size(); a++) {
if (device.getName().equals(pairedDevices.get(a))) { //log cat complains at this line
s = "Paired";
break;
}
}
// matt-hp (paired)
listAdapter.add(device.getName() + " " + s + " " + "\n" + device.getAddress());
} else if (BluetoothAdapter.ACTION_DISCOVERY_STARTED.equals(action)) {
//run some code
} else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {
//run some code
} else if (BluetoothAdapter.ACTION_STATE_CHANGED.equals(action)) {
if (btAdapter.getState() == btAdapter.STATE_OFF) {
turnOnBT();
}
}
}
};
registerReceiver(receiver, filter);
IntentFilter filter = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_STARTED);
registerReceiver(receiver, filter);
filter = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
registerReceiver(receiver, filter);
filter = new IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED);
registerReceiver(receiver, filter);
}
#Override
protected void onResume() {
super.onResume();
registerReceiver(receiver, filter);
}
#Override
protected void onPause() {
super.onPause();
unregisterReceiver(receiver);
}
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (resultCode == RESULT_CANCELED) {
Toast.makeText(getApplicationContext(), "Bluetooth must be enabled to continue", Toast.LENGTH_SHORT).show();
finish();
}
}
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
if (btAdapter.isDiscovering()) {
btAdapter.cancelDiscovery();
}
if (listAdapter.getItem(position).contains("Paired")) {
BluetoothDevice selectedDevice = devices.get(position);
ConnectThread connect = new ConnectThread(selectedDevice);
connect.start();
Toast.makeText(getApplicationContext(), "Device is paired", Toast.LENGTH_SHORT).show();
} else {
Toast.makeText(getApplicationContext(), "Device is not paired", Toast.LENGTH_SHORT).show();
}
}
private class ConnectThread extends Thread {
private final BluetoothSocket mmSocket;
private final BluetoothDevice mmDevice;
public ConnectThread(BluetoothDevice device) {
// Use a temporary object that is later assigned to mmSocket,
// because mmSocket is final
BluetoothSocket tmp = null;
mmDevice = device;
// Get a BluetoothSocket to connect with the given BluetoothDevice
try {
// MY_UUID is the app's UUID string, also used by the server code
tmp = device.createRfcommSocketToServiceRecord(MY_UUID);
} catch (IOException e) {
}
mmSocket = tmp;
}
public void run() {
// Cancel discovery because it will slow down the connection
btAdapter.cancelDiscovery();
try {
// Connect the device through the socket. This will block
// until it succeeds or throws an exception
mmSocket.connect();
} catch (IOException connectException) {
// Unable to connect; close the socket and get out
try {
mmSocket.close();
} catch (IOException closeException) {
}
return;
}
// Do work to manage the connection (in a separate thread)
mHandler.obtainMessage(SUCCESS_CONNECT, mmSocket).sendToTarget();
}
/**
* Will cancel an in-progress connection, and close the socket
*/
public void cancel() {
try {
mmSocket.close();
} catch (IOException e) {
}
}
}
private class ConnectedThread extends Thread {
private final BluetoothSocket mmSocket;
private final InputStream mmInStream;
private final OutputStream mmOutStream;
public ConnectedThread(BluetoothSocket socket) {
mmSocket = socket;
InputStream tmpIn = null;
OutputStream tmpOut = null;
// Get the input and output streams, using temp objects because
// member streams are final
try {
tmpIn = socket.getInputStream();
tmpOut = socket.getOutputStream();
} catch (IOException e) {
}
mmInStream = tmpIn;
mmOutStream = tmpOut;
}
public void run() {
byte[] buffer; // buffer store for the stream
int bytes; // bytes returned from read()
// Keep listening to the InputStream until an exception occurs
while (true) {
try {
// Read from the InputStream
buffer = new byte[1024];
bytes = mmInStream.read(buffer);
// Send the obtained bytes to the UI activity
mHandler.obtainMessage(MESSAGE_READ, bytes, -1, buffer)
.sendToTarget();
} catch (IOException e) {
break;
}
}
}
/* Call this from the main activity to send data to the remote device */
public void write(byte[] bytes) {
try {
mmOutStream.write(bytes);
} catch (IOException e) {
}
}
/* Call this from the main activity to shutdown the connection */
public void cancel() {
try {
mmSocket.close();
} catch (IOException e) {
}
}
}
}
MainActivity:
package com.example.asabanov.powersupplytool;
import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent i = new Intent(MainActivity.this, BluetoothActivity.class);
startActivity(i);
}
});
Button Y10Button = (Button) findViewById(R.id.button);
Y10Button.setOnClickListener(new View.OnClickListener(){
public void onClick(View v){
Intent intent = new Intent(MainActivity.this, Y10.class);
startActivity(intent);
}
});
Button Y20Button = (Button) findViewById(R.id.button2);
Y20Button.setOnClickListener(new View.OnClickListener(){
public void onClick(View v){
Intent intent = new Intent(MainActivity.this, Y20.class);
startActivity(intent);
}
});
Button SPAButton = (Button) findViewById(R.id.button3);
SPAButton.setOnClickListener(new View.OnClickListener(){
public void onClick(View v){
Intent intent = new Intent(MainActivity.this, SPA.class);
startActivity(intent);
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_about) {
return true;
}
return super.onOptionsItemSelected(item);
}
}

You should add some values to your pairedDevices = new ArrayList<String>(); before you try get()

BluetoothDevice object may be null. So you should check whether the object of BluetoothDevice is initialized successfully. I modified part of your code as following:
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
if(device != null) {
devices.add(device);
String s = "";
for (int a = 0; a < pairedDevices.size(); a++) {
if (device.getName().equals(pairedDevices.get(a))) { //log cat complains at this line
s = "Paired";
break;
}
}
// matt-hp (paired)
listAdapter.add(device.getName() + " " + s + " " + "\n" + device.getAddress());
}

In your code, device.getName() returns null, thus the exception is thrown when you call the .equals() method on a null object.
You can check the following question to find a solution to your problem -
android BluetoothDevice.getName() return null

When I trying to Click on Paired device list of bluetooth then it will unfortunately , MyApp has stopped message display and my application is closed

When I click on paired device list of Bluetooth, application crashes , and I get a message saying 'MyApp has stopped
When I start my application first time it doesn't show my Paired devices in paired devices list but when i switch off the display and switch it on again it shows.
package com.example.bluetoothapp;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Set;
import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothClass;
import android.bluetooth.BluetoothDevice;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends Activity {
/** Called when the activity is first created. */
ListView listViewPaired;
ListView listViewDetected;
ArrayList<String> arrayListpaired;
Button buttonSearch, buttonOn, buttonDesc, buttonOff;
ArrayAdapter<String> adapter, detectedAdapter;
static HandleSeacrh handleSeacrh;
BluetoothDevice bdDevice;
BluetoothClass bdClass;
ArrayList<BluetoothDevice> arrayListPairedBluetoothDevices;
private ButtonClicked clicked;
ListItemClickedonPaired listItemClickedonPaired;
BluetoothAdapter bluetoothAdapter = null;
ArrayList<BluetoothDevice> arrayListBluetoothDevices = null;
ListItemClicked listItemClicked;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listViewDetected = (ListView) findViewById(R.id.listViewDetected);
listViewPaired = (ListView) findViewById(R.id.listViewPaired);
buttonSearch = (Button) findViewById(R.id.buttonSearch);
buttonOn = (Button) findViewById(R.id.buttonOn);
buttonDesc = (Button) findViewById(R.id.buttonDesc);
buttonOff = (Button) findViewById(R.id.buttonOff);
arrayListpaired = new ArrayList<String>();
bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
clicked = new ButtonClicked();
handleSeacrh = new HandleSeacrh();
arrayListPairedBluetoothDevices = new ArrayList<BluetoothDevice>();
/*
* the above declaration is just for getting the paired bluetooth
* devices; this helps in the removing the bond between paired devices.
*/
listItemClickedonPaired = new ListItemClickedonPaired();
arrayListBluetoothDevices = new ArrayList<BluetoothDevice>();
adapter = new ArrayAdapter<String>(MainActivity.this,
android.R.layout.simple_list_item_1, arrayListpaired);
detectedAdapter = new ArrayAdapter<String>(MainActivity.this,
android.R.layout.simple_list_item_single_choice);
listViewDetected.setAdapter(detectedAdapter);
listItemClicked = new ListItemClicked();
adapter.notifyDataSetChanged();
listViewPaired.setAdapter(adapter);
}
#Override
protected void onStart() {
// TODO Auto-generated method stub
super.onStart();
getPairedDevices();
buttonOn.setOnClickListener(clicked);
buttonSearch.setOnClickListener(clicked);
buttonDesc.setOnClickListener(clicked);
buttonOff.setOnClickListener(clicked);
listViewDetected.setOnItemClickListener(listItemClicked);
listViewPaired.setOnItemClickListener(new OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
long arg3) {
TextView txt = (TextView) arg1;
Toast.makeText(MainActivity.this,
"" + txt.getText().toString(), 1000).show();
}
});
}
private void getPairedDevices() {
Set<BluetoothDevice> pairedDevice = bluetoothAdapter.getBondedDevices();
if (pairedDevice.size() > 0) {
for (BluetoothDevice device : pairedDevice) {
arrayListpaired.add(device.getName() + "\n"
+ device.getAddress());
arrayListPairedBluetoothDevices.add(device);
}
}
}
class ListItemClicked implements OnItemClickListener {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
// TODO Auto-generated method stub
bdDevice = arrayListBluetoothDevices.get(position);
// bdClass = arrayListBluetoothDevices.get(position);
Log.i("Log", "The dvice : " + bdDevice.toString());
/*
* here below we can do pairing without calling the callthread(), we
* can directly call the connect(). but for the safer side we must
* usethe threading object.
*/
// callThread();
// connect(bdDevice);
Boolean isBonded = false;
try {
isBonded = createBond(bdDevice);
if (isBonded) {
// arrayListpaired.add(bdDevice.getName()+"\n"+bdDevice.getAddress());
getPairedDevices();
}
} catch (Exception e) {
e.printStackTrace();
}// connect(bdDevice);
Log.i("Log", "The bond is created: " + isBonded);
}
}
class ListItemClickedonPaired implements OnItemClickListener {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
bdDevice = arrayListPairedBluetoothDevices.get(position);
try {
Boolean removeBonding = removeBond(bdDevice);
if (removeBonding) {
arrayListpaired.remove(position);
}
Log.i("Log", "Removed" + removeBonding);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
/*
* private void callThread() { new Thread(){ public void run() { Boolean
* isBonded = false; try { isBonded = createBond(bdDevice); if(isBonded) {
* arrayListpaired.add(bdDevice.getName()+"\n"+bdDevice.getAddress());
* adapter.notifyDataSetChanged(); } } catch (Exception e) { // TODO
* Auto-generated catch block e.printStackTrace(); }//connect(bdDevice);
* Log.i("Log", "The bond is created: "+isBonded); } }.start(); }
*/
private Boolean connect(BluetoothDevice bdDevice) {
Boolean bool = false;
try {
Log.i("Log", "service method is called ");
Class cl = Class.forName("android.bluetooth.BluetoothDevice");
Class[] par = {};
Method method = cl.getMethod("createBond", par);
Object[] args = {};
bool = (Boolean) method.invoke(bdDevice);// , args);// this invoke
// creates the detected
// devices paired.
// Log.i("Log", "This is: "+bool.booleanValue());
// Log.i("Log", "devicesss: "+bdDevice.getName());
} catch (Exception e) {
Log.i("Log", "Inside catch of serviceFromDevice Method");
e.printStackTrace();
}
return bool.booleanValue();
};
public boolean removeBond(BluetoothDevice btDevice) throws Exception {
Class btClass = Class.forName("android.bluetooth.BluetoothDevice");
Method removeBondMethod = btClass.getMethod("removeBond");
Boolean returnValue = (Boolean) removeBondMethod.invoke(btDevice);
return returnValue.booleanValue();
}
public boolean createBond(BluetoothDevice btDevice) throws Exception {
Class class1 = Class.forName("android.bluetooth.BluetoothDevice");
Method createBondMethod = class1.getMethod("createBond");
Boolean returnValue = (Boolean) createBondMethod.invoke(btDevice);
return returnValue.booleanValue();
}
class ButtonClicked implements OnClickListener {
#Override
public void onClick(View view) {
switch (view.getId()) {
case R.id.buttonOn:
onBluetooth();
break;
case R.id.buttonSearch:
arrayListBluetoothDevices.clear();
startSearching();
break;
case R.id.buttonDesc:
makeDiscoverable();
break;
case R.id.buttonOff:
offBluetooth();
break;
default:
break;
}
}
}
private BroadcastReceiver myReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
Message msg = Message.obtain();
String action = intent.getAction();
if (BluetoothDevice.ACTION_FOUND.equals(action)) {
Toast.makeText(context, "ACTION_FOUND", Toast.LENGTH_SHORT)
.show();
BluetoothDevice device = intent
.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
try {
// device.getClass().getMethod("setPairingConfirmation",
// boolean.class).invoke(device, true);
// device.getClass().getMethod("cancelPairingUserInput",
// boolean.class).invoke(device);
} catch (Exception e) {
Log.i("Log", "Inside the exception: ");
e.printStackTrace();
}
if (arrayListBluetoothDevices.size() < 1) // this checks if the
// size of bluetooth
// device is 0,then
// add the
{ // device to the arraylist.
detectedAdapter.add(device.getName() + "\n"
+ device.getAddress());
arrayListBluetoothDevices.add(device);
} else {
boolean flag = true; // flag to indicate that particular
// device is already in the arlist
// or not
for (int i = 0; i < arrayListBluetoothDevices.size(); i++) {
if (device.getAddress().equals(
arrayListBluetoothDevices.get(i).getAddress())) {
flag = false;
}
}
if (flag == true) {
detectedAdapter.add(device.getName() + "\n"
+ device.getAddress());
arrayListBluetoothDevices.add(device);
}
}
}
}
};
private void startSearching() {
Log.i("Log", "in the start searching method");
IntentFilter intentFilter = new IntentFilter(
BluetoothDevice.ACTION_FOUND);
MainActivity.this.registerReceiver(myReceiver, intentFilter);
bluetoothAdapter.startDiscovery();
}
private void onBluetooth() {
if (!bluetoothAdapter.isEnabled()) {
bluetoothAdapter.enable();
Log.i("Log", "Bluetooth is Enabled");
}
}
private void offBluetooth() {
if (bluetoothAdapter.isEnabled()) {
bluetoothAdapter.disable();
}
}
private void makeDiscoverable() {
Intent discoverableIntent = new Intent(
BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
discoverableIntent.putExtra(
BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300);
startActivity(discoverableIntent);
Log.i("Log", "Discoverable ");
}
class HandleSeacrh extends Handler {
#Override
public void handleMessage(Message msg) {
switch (msg.what) {
case 111:
break;
default:
break;
}
}
}
}

Communication Android to PC using bluetooth to send a text file

Hello I am new to Android. I want to communicate android with pc to send a text file.
I am trying to communicate using following code.
I am using bluetooth dongle to pc.
When i run application it get crashed without any error. Please help me in communication.
enter code here
package com.exam.bluetooth2;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Set;
import java.util.UUID;
import android.R;
import android.annotation.SuppressLint;
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.EditText;
import android.widget.Toast;
public class Main 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;
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);
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
setContentView(R.layout.activity_list_item);
mScan = (Button) findViewById(R.id.button1);
mScan.setOnClickListener(new View.OnClickListener()
{
public void onClick(View mView)
{
mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
if (mBluetoothAdapter == null)
{
Toast.makeText(Main.this, "Message1", 2000).show();
}
else
{
if (!mBluetoothAdapter.isEnabled())
{
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
}
else
{
ListPairedDevices();
Intent connectIntent = new Intent(Main.this, DeviceListActivity.class);
startActivityForResult(connectIntent, REQUEST_CONNECT_DEVICE);
}
}
}
});
}
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();
Toast.makeText(getBaseContext(), mBluetoothDevice.getAddress(), 10000).show();
//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(Main.this, DeviceListActivity.class);
startActivityForResult(connectIntent, REQUEST_CONNECT_DEVICE);
}
else
{
Toast.makeText(Main.this, "Message", 2000).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());
}
}
// Object device = null;
// String dv = device.toString();
// if(dv.contains("00:1B:EE:82:31:1E"))
// {
// mBluetoothDevice = (BluetoothDevice) device;
// }
}
public void run()
{
try
{
mBluetoothSocket = mBluetoothDevice.createRfcommSocketToServiceRecord(applicationUUID);
mBluetoothAdapter.cancelDiscovery();
mBluetoothSocket.connect();
mHandler.sendEmptyMessage(0);
String messsage = "Welcome to SmarTec";
byte[] tosend=messsage.getBytes();
OutputStream out=mBluetoothSocket.getOutputStream();
out.write(tosend);
}
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(Main.this, "Device Connected", 5000).show();
// Intent in = new Intent(getBaseContext(), Option.class);
// startActivity(in);
}
};
/* public void sendtext(View v) {//button click
Set<BluetoothDevice> bd = mBluetoothAdapter.getBondedDevices();
sendDataToPairedDevice("message1");
}
private void sendDataToPairedDevice(String message ){
byte[] toSend = message.getBytes();
try {
UUID applicationUUID = UUID.fromString("8ce255c0-200a-11e0-ac64- 0800200c9a66");
BluetoothSocket socket = mBluetoothDevice.createInsecureRfcommSocketToServiceRecord(applicationUUID);
OutputStream mmOutStream = socket.getOutputStream();
mmOutStream.write(toSend);
} catch (IOException e) {
Log.e( "Exception during write", e.toString());
}
}
*/
}
enter code here
package com.exam.bluetooth2;
import java.util.Set;
import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.Window;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;
public class DeviceListActivity extends Activity
{
protected static final String TAG = "TAG";
private BluetoothAdapter mBluetoothAdapter;
private ArrayAdapter<String> mPairedDevicesArrayAdapter;
#Override
protected void onCreate(Bundle mSavedInstanceState)
{
super.onCreate(mSavedInstanceState);
requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
setContentView(R.layout.device_list);
setResult(Activity.RESULT_CANCELED);
mPairedDevicesArrayAdapter = new ArrayAdapter<String>(this, R.layout.device_name);
ListView mPairedListView = (ListView) findViewById(R.id.paired_devices);
mPairedListView.setAdapter(mPairedDevicesArrayAdapter);
mPairedListView.setOnItemClickListener(mDeviceClickListener);
mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
Set<BluetoothDevice> mPairedDevices = mBluetoothAdapter.getBondedDevices();
if (mPairedDevices.size() > 0)
{
findViewById(R.id.title_paired_devices).setVisibility(View.VISIBLE);
for (BluetoothDevice mDevice : mPairedDevices)
{
mPairedDevicesArrayAdapter.add(mDevice.getName() + "\n" + mDevice.getAddress());
}
}
else
{
String mNoDevices = getResources().getText(R.string.none_paired).toString();
mPairedDevicesArrayAdapter.add(mNoDevices);
}
}
#Override
protected void onDestroy()
{
super.onDestroy();
if (mBluetoothAdapter != null)
{
mBluetoothAdapter.cancelDiscovery();
}
}
private OnItemClickListener mDeviceClickListener = new OnItemClickListener()
{
public void onItemClick(AdapterView<?> mAdapterView, View mView, int mPosition, long mLong)
{
mBluetoothAdapter.cancelDiscovery();
String mDeviceInfo = ((TextView) mView).getText().toString();
String mDeviceAddress = mDeviceInfo.substring(mDeviceInfo.length() - 17);
Log.v(TAG, "Device_Address " + mDeviceAddress);
Bundle mBundle = new Bundle();
mBundle.putString("DeviceAddress", mDeviceAddress);
Intent mBackIntent = new Intent();
mBackIntent.putExtras(mBundle);
setResult(Activity.RESULT_OK, mBackIntent);
finish();
}
};
}

Vijay,
You need to check few thinks below:
Add bluetooth permission in manifest file.
If device is not supporting bluetooth, then you get bluetooth adapter value null. So need to check that also.
Also its better to create broadcast receiver with bluetooth actions.