title: My Bluetooth app crashes randomly with the error: Error receiving broadCast Intent
body: <p>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 <code>if (device.getName().equals(pairedDevices.get(a))) {</code> but I don't understand what that has to do with the crash?</p>
  
  <p>Any help is appreciated!</p>
  
  <p><strong>Logcat:</strong></p>
  
  <pre><code>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) 
  </code></pre>
  
  <p><strong>BluetoothActivity:</strong></p>
  
  <pre><code>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&lt;String&gt; listAdapter;
      ListView listView;
      BluetoothAdapter btAdapter;
      Set&lt;BluetoothDevice&gt; devicesArray;
      ArrayList&lt;String&gt; pairedDevices;
      ArrayList&lt;BluetoothDevice&gt; 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() &gt; 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&lt;String&gt;(this, android.R.layout.simple_list_item_1, 0);
          listView.setAdapter(listAdapter);
          btAdapter = BluetoothAdapter.getDefaultAdapter();
          pairedDevices = new ArrayList&lt;String&gt;();
          filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
          devices = new ArrayList&lt;BluetoothDevice&gt;();
          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 &lt; 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&lt;?&gt; 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) {
              }
          }
      }
  }
  </code></pre>
  
  <p><strong>MainActivity:</strong></p>
  
  <pre><code>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);
  
      }
  }
  </code></pre>