Develop Reference

Sending events through bluetooth in android

I have created a bluetooth connection between two phones(the paired device don't have my app). How to send events to the phone like screen lock/ volume up
BluetoothAdapter bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
if (bluetoothAdapter.isEnabled()){
handler.sendEmptyMessageDelayed(connectionCheckTimeout,30000);
BluetoothReciever bluetoothReciever = new BluetoothReciever();
bluetoothReciever.registerBluetoothRecieverForConnection(this,this);
SocketThread socketThread = SocketThread.getInstance();
socketThread.registerBluetoothRecieverForCommunication(this,this);
Thread thread = new Thread(socketThread);
thread.start();
}
my socket thread class is here, i am getting a connected device(not just paired).
Now i have to send events like volume up/down to the other device which doesn't run my app.
public class SocketThread implements Runnable {
private static SocketThread ourInstance = new SocketThread();
BluetoothAdapter bluetoothAdapter;
BluetoothDevice device;
BluetoothSocket bluetoothSocket;
static BluetoothSocketListener bluetoothSocketListener;
public static SocketThread getInstance() {
return ourInstance;
}
private SocketThread() {
}
#Override
public void run() {
bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
device = connectedDevice(bluetoothAdapter);
if (device!=null){
// Toast.makeText(getApplicationContext(),"connected to "+device.getName(),Toast.LENGTH_SHORT).show();
if (bluetoothSocketListener!=null) {
bluetoothSocketListener.deviceIsConnected(device,bluetoothSocket);
}
try {
bluetoothSocket.getOutputStream().flush();
} catch (IOException e) {
e.printStackTrace();
}
}else{
if (bluetoothSocketListener!=null) {
bluetoothSocketListener.deviceIsNotConnected();
}
}
}
private BluetoothDevice connectedDevice(BluetoothAdapter bluetoothAdapter){
if (bluetoothAdapter == null)
bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
if (bluetoothAdapter.getBondedDevices().size() == 0)
return null;
//now create socket to all paired devices. Check if connected. then return true
Set<BluetoothDevice> btDevices = bluetoothAdapter.getBondedDevices();
for (BluetoothDevice device : btDevices){
Log.d("main activity"," trying to create socket for paired device "+device.getName());
try {
bluetoothSocket
= device.createRfcommSocketToServiceRecord(device.getUuids()[0].getUuid());
bluetoothSocket.connect();
if (bluetoothSocket.isConnected()){
return device;
}
} catch (IOException e) {
e.printStackTrace();
}
}
return null;
}
public void registerBluetoothRecieverForCommunication(Context context, BluetoothSocketListener bluetoothSocketListener){
this.bluetoothSocketListener = bluetoothSocketListener;
}
}

Bluetooth sends raw data. Apparently, you have to parse those somehow and transform into calls in your app, doing some work

android Bluetooth crash when connection is stopped

I am writing an app on Android Studio.
I communicate from an Android device to an arduino board via Bluetooth.
For now everything works but i am starting a new Activity and i need to stop the actual BT connection. so i want to call a stop method.
The problem is that it crash when i call it.
here is the code
public class BtInterface {
private BluetoothDevice device = null;
private BluetoothSocket socket = null;
private InputStream receiveStream = null;
private OutputStream sendStream = null;
String GlobalBuff="";
String Right_Buff="";
private ReceiverThread receiverThread;
Handler handler;
public BtInterface(Handler hstatus, Handler h,String Device_Name) {
Set<BluetoothDevice> setpairedDevices = BluetoothAdapter.getDefaultAdapter().getBondedDevices();
BluetoothDevice[] pairedDevices = (BluetoothDevice[]) setpairedDevices.toArray(new BluetoothDevice[setpairedDevices.size()]);
for(int i=0;i<pairedDevices.length;i++) {
if(pairedDevices[i].getName().contains(Device_Name)) {
device = pairedDevices[i];
try {
socket = device.createRfcommSocketToServiceRecord(UUID.fromString("00001101-0000-1000-8000-00805F9B34FB"));
receiveStream = socket.getInputStream();
sendStream = socket.getOutputStream();
} catch (IOException e) {
e.printStackTrace();
}
break;
}
}
handler = hstatus;
receiverThread = new ReceiverThread(h);
}
public void sendData(String data) {
sendData(data, false);
}
public void sendData(String data, boolean deleteScheduledData) {
try {
sendStream.write(data.getBytes());
sendStream.flush();
} catch (IOException e) {
e.printStackTrace();
}
}
public void connect() {
new Thread() {
#Override public void run() {
try {
socket.connect();
Message msg = handler.obtainMessage();
msg.arg1 = 1;
handler.sendMessage(msg);
receiverThread.start();
} catch (IOException e) {
Log.v("N", "Connection Failed : " + e.getMessage());
e.printStackTrace();
}
}
}.start();
}
public void close() {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
socket=null; //???
}
public BluetoothDevice getDevice() {
return device;
}
private class ReceiverThread extends Thread {
Handler handler;
ReceiverThread(Handler h) {
handler = h;
}
#Override public void run() {
while(true) {
try {
if(receiveStream.available() > 0) {
byte buffer[] = new byte[1000];
int k = receiveStream.read(buffer, 0, 1000);
if(k > 0) {
byte rawdata[] = new byte[k];
for(int i=0;i<k;i++)
rawdata[i] = buffer[i];
String data = new String(rawdata);
GlobalBuff= GlobalBuff+data;
Right_Buff= GlobalBuff.substring(GlobalBuff.length()-1,GlobalBuff.length());
if(Right_Buff.equals("\n")){
Message msg = handler.obtainMessage();
Bundle b = new Bundle();
b.putString("receivedData", GlobalBuff);
msg.setData(b);
handler.sendMessage(msg);
GlobalBuff="";
}
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
i try some extra code :
receiverThread.interrupt();
receiverThread=null;
if (receiveStream != null) {
try {receiveStream.close();} catch (Exception e) {}
receiveStream = null;
}
if (sendStream != null) {
try {sendStream.close();} catch (Exception e) {}
sendStream = null;
}
before closing but the result is the same , it crash.
The strange behavior is that it didn't crash immediately as it could happen with a type error or else ( i am talking of the behavior in debug mode...)
If anybody got an idea.
Googling this bring me to people with this issue but no solution that works for my case.
Thanks
UPDATE
what i found as a trace when it crash is that :
06-02 07:45:27.369 9025-9133/fr.icservice.sechage A/libc? Fatal signal 11 (SIGSEGV) at 0x00000008 (code=1), thread 9133 (Thread-1436)
I also made a test on a sony Z3 phone under 5.0.2 (compare to my T210 samsung galaxy tab3 under 4.4.2)and it not crash..!
maybe it's a ROM bug?! or a android version problem...

This is a known problem (or bug?) on Android. If you close the Bluetooth socket and then access it later on, some devices will crash with a segmentation fault (like yours). A common workaround is to check socket.isConnected() before or to synchronize the access to close(), write(), read(), ... by setting a flag like closeWasCalled = true and prevent any further calls to methods of this socket in your code after a close() call.

The problem comes with Socket Input/Output. I faced this problem when disconnecting with peer bluetooth device.
Reason :
From code, we are trying to read() , write() from socket object/connection which is closed.
Solution :
Add checking socket.isConnected() before above operations
You can read more about this problem on Stack Overflow question : Here

Create a listening stuck at listenUsingRfcommWithServiceRecord

I am using Bluetooth API of android. I am here creating client-server connection using BluetoothServerSocket & BluetoothSocket but my program stuck at the certain point.
// Create a BroadcastReceiver for ACTION_FOUND
private BroadcastReceiver mReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
// When discovery find a device
if (BluetoothDevice.ACTION_FOUND.equals(action)) {
// get the BluetoothDevice object from the Intent
BluetoothDevice mBluetoothDevice = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
Log.i("MainActivity", "Device Name: " + mBluetoothDevice.getName() + " Address: " + mBluetoothDevice.getAddress());
new AcceptThread().start();
}
}
};
private class AcceptThread extends Thread {
private BluetoothServerSocket mBluetoothServerSocket ;
public AcceptThread() {
try {
mBluetoothServerSocket = mBluetoothAdapter.listenUsingRfcommWithServiceRecord("BT_SERVER", UUID.fromString("a60f35f0-b93a-11de-8a39-08002009c666"));
} catch (IOException e) {
Log.e("MainActivity", e.getMessage());
}
}
#Override
public void run() {
BluetoothSocket mBluetoothSocket;
// Keep listening until exception occurs or a socket is returned
while(true) {
try {
mBluetoothSocket = mBluetoothServerSocket.accept();
} catch (IOException e) {
break;
}
// If a connection was accepted
if(mBluetoothSocket != null) {
// transfer the data here
Toast.makeText(MainActivity.this, "Socket is created", Toast.LENGTH_LONG).show();;
try {
// close the connection to stop to listen any connection now
mBluetoothSocket.close();
} catch(IOException e) { }
}
}
}
}
Here my program stuck
mBluetoothServerSocket = mBluetoothAdapter.listenUsingRfcommWithServiceRecord("BT_SERVER", UUID.fromString("a60f35f0-b93a-11de-8a39-08002009c666"));
I could not catch why it getting stuck at this point, Any idea to you for this ?

From your question it is unclear whether your application is a client or server or both. For writing bluetooth client-server applications, android phone at any instance plays a single role of server or a client. If your phone is server, then you need to listen for connections from other bluetooth devices using method listenUsingRfcommWithServiceRecord(). Then use accept() to complete the connection.
In case android phone acts as client, it will initiate a bluetooth connection to other devices. For such scenario, your broadcast receiver is needed. We need to scan for available bluetooth devices with startDiscovery() method. Your broadcast receiver's onReceive() is called when a new bluetooth device is found. To connect to this found device, call createRfcommSocketToServiceRecord() with desired UUID.
Hope this helps.

This may be obvious but did you instantiate your BluetoothAdapter? Accept Thread uses the adapter without intializing it.
myBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

While listening, set the discovery name to a specific value then used listenUsingRfcommWithServiceRecord method in broadcast receiver.
private class AcceptTask extends AsyncTask<UUID,Void,BluetoothSocket> {
#Override
protected BluetoothSocket doInBackground(UUID... params) {
String name = mBtAdapter.getName();
try {
//While listening, set the discovery name to a specific value
mBtAdapter.setName(SEARCH_NAME);
BluetoothServerSocket socket = mBtAdapter.listenUsingRfcommWithServiceRecord("BluetoothRecipe", params[0]);
BluetoothSocket connected = socket.accept();
//Reset the BT adapter name
mBtAdapter.setName(name);
return connected;
} catch (IOException e) {
e.printStackTrace();
mBtAdapter.setName(name);
return null;
}
}
#Override
protected void onPostExecute(BluetoothSocket socket) {
if(socket == null) {
return;
}
mBtSocket = socket;
ConnectedTask task = new ConnectedTask();
task.execute(mBtSocket);
}
}
// End

Thread blocking UI in android

I am using this sample code from the Android Bluetooth guide, found here http://developer.android.com/guide/topics/connectivity/bluetooth.html under "Connecting as a Client".
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
mBluetoothAdapter.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)
manageConnectedSocket(mmSocket);
}
/** Will cancel an in-progress connection, and close the socket */
public void cancel() {
try {
mmSocket.close();
} catch (IOException e) { }
}
}
In my onCreate, I call
protected void onCreate(Bundle savedInstanceState) {
setContentView(R.layout.activity_main);
super.onCreate(savedInstanceState);
connectionManager= new ConnectionManager(this);
connectionManager.start();
The connectionManager launches a ConnectThread and the connect thread successfully connects to another bluetooth device. However, the layout isn't rendered until the ConnectThread returns (exactly, when mmSocket.connect() stops blocking).
How can I get the layout to display first?

In stead of creating the connection manager from the UI Thread, why dont you create it in a worker thread as follows:
protected void onCreate(Bundle savedInstanceState) {
setContentView(R.layout.activity_main);
super.onCreate(savedInstanceState);
new Thread(new Runnable() {
#Override
public void run() {
connectionManager= new ConnectionManager(YourActivity.this);
connectionManager.start();
}
}).start();
This way you never get to block the UI Thread, hope this helps...
Regards!

You can wrap it in an async task
http://developer.android.com/reference/android/os/AsyncTask.html

Remember, setContentView() only takes action once the onCreate() method returns. Taking this into account, you should run the code in another thread and not in the UI thread.
Your code should look something like this:
protected void onCreate(Bundle savedInstanceState) {
setContentView(R.layout.activity_main);
super.onCreate(savedInstanceState);
new Thread(new Runnable() {
#Override
public void run() {
connectionManager= new ConnectionManager(this);
connectionManager.start();
}
}).start();
}

android bluetooth can't connect

I've been having this problem for a while and haven't been able to figure it out.
I have a android application that puts all paired devices in a listview. When you click one of the list items, it will initiate a request to connect to that bluetooth device.
I can get the list of devices with their addresses no problem.
The problem is that once I try to connect I get an IOException on socket.connect();
The error message is as follows:
"connect read failed, socket might closed or timeout, read ret: -1"
Here is my code. ANY suggestions would be appreciated. I'm pretty stuck on this.
fyi: the "onEvent" methods is a library that simplifies callbacks...that part works.
When the user clicks on a list items this method is called "public void onEvent(EventMessage.DeviceSelected event)"
public class EcoDashActivity extends BaseActivity {
public static final UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
private BluetoothAdapter mBluetoothAdapter;
private int REQUEST_ENABLE_BT = 100;
private ArrayList<BluetoothDevice> mDevicesList;
private BluetoothDeviceDialog mDialog;
private ProgressDialog progressBar;
private int progressBarStatus = 0;
private Handler progressBarHandler = new Handler();
#Override
public void onCreate(final Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.main);
mDevicesList = new ArrayList<BluetoothDevice>();
// Register the BroadcastReceiver
IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
registerReceiver(mReceiver, filter);
setupBluetooth();
}
private void setupBluetooth() {
mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
if (mBluetoothAdapter == null) {
// Device does not support Bluetooth
Toast.makeText(this, "Device does not support Bluetooth", Toast.LENGTH_SHORT).show();
}
if (!mBluetoothAdapter.isEnabled()) {
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
} else {
searchForPairedDevices();
mDialog = new BluetoothDeviceDialog(this, mDevicesList);
mDialog.show(getFragmentManager(), "");
}
}
private void searchForPairedDevices() {
Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices();
// If there are paired devices
if (pairedDevices.size() > 0) {
// Loop through paired devices
for (BluetoothDevice device : pairedDevices) {
// Add the name and address to an array adapter to show in a ListView
mDevices.add(device.getName() + "\n" + device.getAddress());
mDevicesList.add(device);
}
}
}
private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
// When discovery finds a device
if (BluetoothDevice.ACTION_FOUND.equals(action)) {
// Get the BluetoothDevice object from the Intent
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
// Add the name and address to an array adapter to show in a ListView
mDevicesList.add(device);
}
}
};
#Override
protected void onDestroy() {
super.onDestroy();
unregisterReceiver(mReceiver);
}
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == REQUEST_ENABLE_BT) {
if (resultCode == RESULT_OK) {
Toast.makeText(this, "BT turned on!", Toast.LENGTH_SHORT).show();
searchForPairedDevices();
mDialog = new BluetoothDeviceDialog(this, mDevicesList);
mDialog.show(getFragmentManager(), "");
}
}
super.onActivityResult(requestCode, resultCode, data);
}
public void onEvent(EventMessage.DeviceSelected event) {
mDialog.dismiss();
BluetoothDevice device = event.getDevice();
ConnectThread connectThread = new ConnectThread(device);
connectThread.start();
}
public 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() {
setName("ConnectThread");
// Cancel discovery because it will slow down the connection
mBluetoothAdapter.cancelDiscovery();
try {
// Connect the device through the socket. This will block
// until it succeeds or throws an exception
Log.d("kent", "trying to connect to device");
mmSocket.connect();
Log.d("kent", "Connected!");
} catch (IOException connectException) {
// Unable to connect; close the socket and get out
try {
Log.d("kent", "failed to connect");
mmSocket.close();
} catch (IOException closeException) { }
return;
}
Log.d("kent", "Connected!");
}
/** Will cancel an in-progress connection, and close the socket */
public void cancel() {
try {
mmSocket.close();
} catch (IOException e) { }
}
}
Here is my logcat. Pretty short.
07-22 10:37:05.129: DEBUG/kent(17512): trying to connect to device
07-22 10:37:05.129: WARN/BluetoothAdapter(17512): getBluetoothService() called with no BluetoothManagerCallback
07-22 10:37:05.129: DEBUG/BluetoothSocket(17512): connect(), SocketState: INIT, mPfd: {ParcelFileDescriptor: FileDescriptor[98]}
07-22 10:37:40.757: DEBUG/dalvikvm(17512): GC_CONCURRENT freed 6157K, 9% free 62793K/68972K, paused 7ms+7ms, total 72ms
07-22 10:38:06.975: DEBUG/kent(17512): failed to connect
07-22 10:38:06.975: DEBUG/kent(17512): read failed, socket might closed or timeout, read ret: -1
That last line is in the "Catch" section of a try/catch...I'm just logging the error message.
Please note, there is about a 20 second gap between "trying to connect to device" and "failed to connect"

The jelly bean bluetooth stack is markedly different from the other versions.
This might help: http://wiresareobsolete.com/wordpress/2010/11/android-bluetooth-rfcomm/
In gist:
The UUID is a value that must point to a published service on your embedded device, it is not just randomly generated. The RFCOMM SPP connection you want to access has a specific UUID that it publishes to identify that service, and when you create a socket it must match the same UUID.
If you are targeting 4.0.3 device and above , use fetchUuidsWithSdp() and getUuids() to find all the published services and their associated UUID values. For backward compatibility read the article

I got the same error message after connecting the socket a second time. I simply checked if the socket is already connected.
if(!mmSocket.isConnected())
mmSocket.connect();
I was testing on Android 4.4.2 (Moto G).