android - Application force close when printer device off -

i developed app can connect device printer.

firstly connect app device, when printer device off application force closed, dont know why happens on devices.

below script connect it:

public boolean openbtbyaddress(context _context,string address) {     activity activity = (activity) _context;     boolean cek = false;     try {         mbluetoothadapter = bluetoothadapter.getdefaultadapter();          if(mbluetoothadapter == null) {             //  mylabel.settext("no bluetooth adapter available");             toast.maketext(_context,"no bluetooth adapter available",toast.length_short).show();             cek= false;         }          if(!mbluetoothadapter.isenabled()) {             intent enablebluetooth = new intent(bluetoothadapter.action_request_enable);             activity.startactivityforresult(enablebluetooth, 0);         }          set<bluetoothdevice> paireddevices = mbluetoothadapter.getbondeddevices();           if(paireddevices.size() > 0) {             (bluetoothdevice device : paireddevices) {                 bluetoothdevice da = device;                 // rpp300 name of bluetooth printer device                 // got name list of paired devices                 if (device.getaddress().equals(address)) {                      cek= openbt(device,_context);                     //mmdevice = device;                     break;                 }              }         }         else         {             cek= false;         }          }catch(exception e){         e.printstacktrace();         cek= false;     }      return cek; }  private boolean openbt(bluetoothdevice bd,context _context ) throws ioexception {      boolean cek = false;     try {         uuid uuid = uuid.fromstring("00001101-0000-1000-8000-00805f9b34fb");         mmsocket = bd.createrfcommsockettoservicerecord(uuid);         mmsocket.connect();         mmoutputstream = mmsocket.getoutputstream();         mminputstream = mmsocket.getinputstream();          beginlistenfordata();         toast.maketext(_context,"connect_success",toast.length_short).show();         cek =true;      } catch (exception e) {         e.printstacktrace();         toast.maketext(_context,"connect_failed",toast.length_short).show();         cek =false ;      }     return cek; }  private void beginlistenfordata() {     try {         final handler handler = new handler();          final byte delimiter = 10;          stopworker = false;         readbufferposition = 0;         readbuffer = new byte[1024];          workerthread = new thread(new runnable() {             public void run() {                  while (!thread.currentthread().isinterrupted() && !stopworker) {                      try {                         if(mminputstream != null) {                             int bytesavailable = mminputstream.available();                             if (bytesavailable > 0) {                                 byte[] packetbytes = new byte[bytesavailable];                                 mminputstream.read(packetbytes);                                  (int = 0; < bytesavailable; i++) {                                      byte b = packetbytes[i];                                     if (b == delimiter) {                                          byte[] encodedbytes = new byte[readbufferposition];                                         system.arraycopy(                                                 readbuffer, 0,                                                 encodedbytes, 0,                                                 encodedbytes.length                                         );                                         final string data = new string(encodedbytes, "us-ascii");                                         readbufferposition = 0;                                         // tell user data sent bluetooth printer device                                         handler.post(new runnable() {                                             public void run() {                                             }                                         });                                     } else {                                         readbuffer[readbufferposition++] = b;                                     }                                 }                             }                         }                      } catch (ioexception ex) {                         stopworker = true;                     }                  }             }         });          workerthread.start();      } catch (exception e) {         e.printstacktrace();     } }