Develop Reference

Android BLE data in different characteristic exchange when onCharacteristicChanged

I have a sensor it will notify data with fixed length in different characteristic.
The Char3 only notify data with 48 bytes.
The Char4 only notify data with 240 bytes.
When I use the Redmi note T8 to develop my android app.
I sometimes see 240 bytes in char3 and the 48 bytes in Char4.
The data are exchange. That's so weired
I also use nrfConnect/lightBlue to check the characteristic data change.
and use different mobile device to develop (Samsung SM-T510) with the same code.
I also don't see the situation I mention before.
I also try to add mutex to broadcastUpdate function, but it doesn't work.
Is there anyone face this issue?
And, Here is my related code in Android.
private val mBluetoothGatt0Callback = object : BluetoothGattCallback() {
...
override fun onCharacteristicChanged(
gatt: BluetoothGatt?,
characteristic: BluetoothGattCharacteristic?
) {
super.onCharacteristicChanged(gatt, characteristic)
when (characteristic?.uuid) {
Profile.CHAR3_UUID -> {
broadcastUpdate(Action.IMU_DataComing, gatt!!, characteristic!!)
}
Profile.CHAR4_UUID ->{
broadcastUpdate(Action.EMG_DataComing, gatt!!, characteristic!!)
}
}
}
...
}
private fun broadcastUpdate(action: String, gatt: BluetoothGatt, char: BluetoothGattCharacteristic) {
val intent = Intent(action)
var serialNum = -1;
for (i in 0..3) {
if (gatt == mBluetoothGatt[i]) {
serialNum = i
break;
}
}
intent.putExtra("SerialNum", serialNum)
val msg = char.value
if (action == Action.IMU_DataComing) {
if (msg.size != 48) {
Log.i("Test", "IMU ${msg.size}")
return
}
intent.putExtra("IMU_DATA_MSG", msg)
} else if (action == Action.EMG_DataComing) {
if (msg.size != 240) {
Log.i("Test", "EMG ${msg.size}")
return
}
intent.putExtra("EMG_DATA_MSG", msg)
}
sendBroadcast(intent)
}

How to receive data from BLE device using greenbot EventBus in my code?

I have an application that sends and receives data using BLE. Originally it was classical bluetooth but I was tasked with changing the project to BLE.
So far I have succeeded in sending data but not receiving it. The main activity contains multiple fragments. On of those is responsible for sending data where as the other sends a request and then receives a response with the data from the BLE device.
one fragment is called Parameter and the other Memory. Each fragment has a viewmodel and repository as the architecture is based on MVVM. the flow is as follows:
Parameter fragment -> View model -> repository -> DataStore class -> DataStore uses instance from BLEConnectionManager class to send the data of the corresponding parameter. Example of a function in DataStore:
fun sendToolAddressParam(data: Int){
toolAddress = data
var value = Integer.toHexString(data)
if (value.length == 1) value = "0$value"
val message = WriteCommandCodes.TOOL_ADDRESS.value + " " + value + " " + WriteCommandCodes.EXTRA2.value
BleConnectionManager.sendMessage(message)
Timber.i("Payload: $message")
}
There are also functions that request data:
fun requestToolAddress(){
BleConnectionManager.requestReadValues(ReadRequestCodes.TOOL_ADDRESS.value)
}
in the BLE class the functions are written as the following:
fun write(message:String){
val bytes = BigInteger(message.replace("\\s".toRegex(), ""), 16).toByteArray()
Timber.i("Bytes value ---> ${bytes.toHexString()}")
val device = getBleDevice()
// val characteristicRX = getBleCharacteristic()
val characteristicRX = bluetoothGattRef.getService(XpressStreamingServiceUUID).getCharacteristic(
peripheralRX)
writeCharacteristic(device, characteristicRX, bytes)
}
fun requestReadValues(requestCode:String){
if(isConnected.value!!){
write(requestCode)
}else{
Timber.e("Make sure that you connected and paired with the desired device.")
}
}
fun sendMessage(message:String){
Timber.i("Check if isConnected = true --> ${isConnected.value}")
if(isConnected.value == true){
write(message)
}else{
Timber.e("Make sure that you connected and paired with the desired device.")
}
}
Now here is my issue I want to receive data from the BLE device after I send the request, the device's documentation when it comes to BLE data exchange is here: https://docs.silabs.com/gecko-os/1/bgx/latest/ble-services
Now I have a function that supposedly receives the incoming messages but this was when classical bluetooth was used.
fun readIncomingMessages(message: String){
when{
message.startsWith(com.brainsocket.milink.data.bluetooth.ReadResponseCodes.KEY_ADDRESS.value) ->{
EventBus.getDefault().post(
ReadKeyAddressEvent(message.substring(com.brainsocket.milink.data.bluetooth.ReadResponseCodes.KEY_ADDRESS.value.length+1, com.brainsocket.milink.data.bluetooth.ReadResponseCodes.KEY_ADDRESS.value.length+3))
)
Timber.i("Message received: $message")
}
message.startsWith(com.brainsocket.milink.data.bluetooth.ReadResponseCodes.TOOL_ADDRESS.value) ->{
EventBus.getDefault().post(
ReadToolAddressEvent(message.substring(com.brainsocket.milink.data.bluetooth.ReadResponseCodes.TOOL_ADDRESS.value.length+1, com.brainsocket.milink.data.bluetooth.ReadResponseCodes.TOOL_ADDRESS.value.length+3))
)
Timber.i("Message received: $message")}
message.startsWith(com.brainsocket.milink.data.bluetooth.ReadResponseCodes.RPM_THRESHOLD.value) ->{
EventBus.getDefault().post(
ReadRPMThresholdEvent(message.substring(com.brainsocket.milink.data.bluetooth.ReadResponseCodes.RPM_THRESHOLD.value.length+1, com.brainsocket.milink.data.bluetooth.ReadResponseCodes.RPM_THRESHOLD.value.length+3))
)
Timber.i("Message received: $message")}
message.startsWith(com.brainsocket.milink.data.bluetooth.ReadResponseCodes.BACKLASH.value) ->{
EventBus.getDefault().post(
ReadBacklashEvent(message.substring(com.brainsocket.milink.data.bluetooth.ReadResponseCodes.BACKLASH.value.length+1, com.brainsocket.milink.data.bluetooth.ReadResponseCodes.BACKLASH.value.length+6))
)
Timber.i("Message received: $message")}
As you can see the Event Bus is used here, it is also used here in the DataStore:
#Subscribe(threadMode = ThreadMode.MAIN)
fun onKeyAddressEvent(event: ReadKeyAddressEvent) {
Timber.i("onKeyAddressEvent: data:${event.data}")
keyAddress = Integer.parseInt(event.data , 16)
EventBus.getDefault().post(ReadMemoryItemsEvent())
}
#Subscribe(threadMode = ThreadMode.MAIN)
fun onToolAddressEvent(event: ReadToolAddressEvent) {
Log.d(LOG_TAG, "onToolAddressEvent: data:${event.data}")
when(Integer.parseInt(event.data , 16)){
0 -> toolAddress = 1
1 -> toolAddress = 2
}
EventBus.getDefault().post(ReadMemoryItemsEvent())
}
#Subscribe(threadMode = ThreadMode.MAIN)
fun onRPMThresholdEvent(event: ReadRPMThresholdEvent) {
Log.d(LOG_TAG, "onRPMThresholdEvent: data:${event.data}")
rpmThreshold = Integer.parseInt(event.data , 16)
EventBus.getDefault().post(ReadMemoryItemsEvent())
}
#Subscribe(threadMode = ThreadMode.MAIN)
fun onReadBacklashEvent(event: ReadBacklashEvent) {
Log.d(LOG_TAG, "onReadBacklashEvent: data:${event.data}")
val data = event.data
backlash = parseGotoPos(data)
EventBus.getDefault().post(ReadMemoryItemsEvent())
}
This is in the repository:
fun getMemoryItems() : List<ModesPosItem> = listOf(
ModesPosItem(value = btDataStore.keyAddress, title = context.getString(R.string.key_address_string)),
ModesPosItem(value = btDataStore.toolAddress, title = context.getString(R.string.tool_address_string)),
ModesPosItem(value = btDataStore.rpmThreshold, title = context.getString(R.string.rpm_threshold_string)),
ModesPosItem(value = btDataStore.backlash, title = context.getString(R.string.backlash_string))
)
This is in the viewmodel:
#Subscribe(threadMode = ThreadMode.MAIN)
fun onReadMemoryItemsEvent(event: ReadMemoryItemsEvent) {
memoryItems.value = repository.getMemoryItems()
Timber.i("Memory Items [tool address, keyAddress, RPM threshold, backlash]: ${memoryItems.value.toString()}")
}
This is in the fragment:
override fun onStart() {
super.onStart()
EventBus.getDefault().register(this)
}
override fun onStop() {
EventBus.getDefault().unregister(this)
super.onStop()
}
What exactly am I supposed to do to acquire the data from the BLE device?

I made an app that write and read continous stream data throw BLE connection from a bluetooth device.
The Flow i follow is the following:
Connect Gatt;
Discover Services;
Write To Characteristic;
Subscribe to Notification;
Read Characteristic from notification --> Here the EventBus post() with your data package;
Going deeper into the connection and using some code:
After you connect to the GATT you call onConnectionStateChange to listen for changes in the gatt connection:
private val gattCallback = object : BluetoothGattCallback() {
override fun onConnectionStateChange(gatt: BluetoothGatt, status: Int, newState: Int) {
val deviceAddress = gatt.device.address
if (status == BluetoothGatt.GATT_SUCCESS) {
if (newState == BluetoothProfile.STATE_CONNECTED) {
Log.w("BluetoothGattCallback", "Successfully connected to $deviceAddress")
// NOW DISCOVER SERVICES
gatt.discoverServices()
} else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
Log.w("BluetoothGattCallback", "Successfully disconnected from $deviceAddress")
}
} else {
Log.w(
"BluetoothGattCallback",
"Error $status encountered for $deviceAddress! Disconnecting..."
)
}
If the GATT is connected succesfully it will discover services.
At this step you can write to the characteristic as follow:
override fun onServicesDiscovered(gatt: BluetoothGatt, status: Int) {
with(gatt) {
Log.w(
"BluetoothGattCallback",
"Discovered ${services.size} services for ${device.address}"
)
val msg = byteArrayOf(0x00.toByte())
val newcharacteristic = gatt!!.getService(dataUUID_service).getCharacteristic(
dataUUID_characteristic
)
newcharacteristic!!.value = msg
gatt!!.writeCharacteristic(newcharacteristic)
}
}
This will let you go on the next step, the onCharacteristicWrite listener:
override fun onCharacteristicWrite(
gatt: BluetoothGatt,
characteristic: BluetoothGattCharacteristic,
status: Int
) {
val characteristic = gatt.getService(dataUUID_service).getCharacteristic(
dataUUID_characteristic
)
gatt.setCharacteristicNotification(characteristic, true)
val descriptor = characteristic!!.getDescriptor(descriptor_UUID)
descriptor.value = BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE;
if (descriptor != null) {
descriptor.value = BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE
gatt.writeDescriptor(descriptor)
}
}
Writing the characteristic will let you go into the onCharacteristicChanged listener that will give you back the data from the ble device and in which you can use the event bus to use your data.
override fun onCharacteristicChanged(
gatt: BluetoothGatt,
charac: BluetoothGattCharacteristic
) {
super.onCharacteristicChanged(gatt, charac)
// Log.d("CHARAC", "Characteristic Changed")
onCharacteristicRead(gatt, charac, BluetoothGatt.GATT_SUCCESS)
}
Where onCharacteristicRead should look like:
override fun onCharacteristicRead(
gatt: BluetoothGatt,
characteristic: BluetoothGattCharacteristic,
status: Int
) {
with(characteristic) {
when (status) {
BluetoothGatt.GATT_SUCCESS -> {
Log.i("BluetoothGattCallback","Read characteristic $uuid:\n${value.toHexString()}" )
// value is the read value from ble device
// HERE YOU HANDE YOUR EVENT BUS, example:
val eventData: deviceListener = deviceListener(value)
EventBus.getDefault().post(eventData)
}
BluetoothGatt.GATT_READ_NOT_PERMITTED -> {
Log.e("BluetoothGattCallback", "Read not permitted for $uuid!")
}
else -> {
Log.e(
"BluetoothGattCallback",
"Characteristic read failed for $uuid, error: $status"
)
}
}
}
}
Maybe it is not the most efficent way and not the clearest code but it works like a charm.

Android, BLE continuously writing a characteristic value disconnects the gatt server

I notice that if i write fast and continuously a characteristic value the gatt server disconnect.
I know that I have to wait until onCharacteristicWrite callback, so that's not the problem I think.
This my queue implementation, I'm using a kotlin Channel to syncronize write and read.
private var continuation: CancellableContinuation<BluetoothGattCharacteristic>? = null
private val channel = Channel<WriteOp>(1)
private suspend fun processBluetoothWrite() {
do {
val writeOp = channel.receiveOrNull()
writeOp?.apply {
try {
suspendCancellableCoroutine<BluetoothGattCharacteristic> { cont ->
continuation = cont
characteristic.value = writeOp?.value
Log.d(TAG, "Write to ${characteristic?.uuid} value ${writeOp?.value?.toHexString()}...")
if (gatt?.writeCharacteristic(characteristic) == false) {
cont.resumeWithException(Exception("Write to ${characteristic?.uuid} fails."))
}
}
} catch (ex: Exception) {
Log.e(TAG, ex.message, ex)
}
}
} while (writeOp != null)
}
override fun onCharacteristicWrite(
gatt: BluetoothGatt?,
characteristic: BluetoothGattCharacteristic?,
status: Int
) {
Log.d(TAG, "Write to ${characteristic?.uuid} value ${characteristic?.value?.toHexString()} | ${status}")
characteristic?.apply {
if (status == BluetoothGatt.GATT_SUCCESS) {
continuation?.resume(this)
} else {
continuation?.resumeWithException(Exception("Write to ${characteristic?.uuid} value ${characteristic?.value?.toHexString()} | ${status}"))
}
}
}
I need to add a delay of about 100ms in the queue processing to avoid disconnection.
UPDATE
After setting writeType as default, it seems that onCharacteristicWrite is more realistic (I used to get GATT_SUCCESS even when the device stopped communicating, so I guess it was a "virtual" state), now when the device stopped communicating it didn't get the onCharacteristicWrite callback, though after a while it is fired with status = 133.
characteristic.writeType = BluetoothGattCharacteristic.WRITE_TYPE_DEFAULT
What does it mean?

Problem writing gatt characteristics to BLE device

I'm trying to write a custom characteristic to a BLE Device using Google's example project .
On the DeviceControlActivity and while I'm looping through the fetched BluetoothGattServices I try to set a characteristic for one of them. At this point I'm just picking one randomly to test.
private void displayGattServices(List<BluetoothGattService> gattServices) {
...
// Loops through available GATT Services.
for (BluetoothGattService gattService : gattServices) {
uuid = gattService.getUuid().toString();
if(uuid.equals("00001800-0000-1000-8000-00805f9b34fb") && !firstTime){
firstTime = true;
BluetoothGattCharacteristic customChar = new BluetoothGattCharacteristic(MY_CHARACTERISTIC,
BluetoothGattCharacteristic.PROPERTY_READ | BluetoothGattCharacteristic.PROPERTY_WRITE,
BluetoothGattCharacteristic.PERMISSION_READ |BluetoothGattCharacteristic.PERMISSION_WRITE);
byte[] val = new byte[20];
val[0] = 71;
val[1] = 97;
val[2] = 108;
val[3] = 97;
val[4] = 120;
val[5] = 121;
val[6] = 32;
val[7] = 70;
val[8] = 105;
val[9] = 116;
val[10] = -30;
val[11] = -109;
val[12] = -108;
val[13] = 32;
val[14] = 40;
val[15] = 70;
val[16] = 57;
val[17] = 66;
val[18] = 57;
val[19] = 41;
customChar.setValue(val);
boolean isAdded = gattService.addCharacteristic(customChar);
Log.d(TAG,"CARAC ADDED? "+isAdded);
}
...
}
This call to addCharacteristic returns true which according to the docs means the writing operation was successful, however when I rescan the services (without executing the code above) I cannot find the BluetoothGattCharacteristic also when I try to read the value of said characteristic I get a status 135. According to this post means GATT_ILLEGAL_PARAMETER
Please note that the byte array is literally copied from another characteristic so normally it should do the trick.
Is it possible that the device I'm trying to write to doesn't support writing ? or the service itself ?
EDIT:
Following the suggestion on the comment, I have tried to modify an existing characteristic using the code below without success (I think the characteristic was created using READ only flag?)
for (BluetoothGattCharacteristic gattCharacteristic : gattCharacteristics) {
...
uuid = gattCharacteristic.getUuid().toString();
// UUID for device name
if(uuid.equals("00002a00-0000-1000-8000-00805f9b34fb") && !firstTime){
firstTime = true;
gattCharacteristic.setValue("Hello");
boolean isAdded = mBluetoothLeService.writeCharacteristic(gattCharacteristic);
Log.d(TAG,"CARAC ADDED? "+isAdded); // returns false
}
I also tried to setup a GattServer and creating a new service with new characteristic but also without any success. Here is the code (this partuses Kotlin):
mBluetoothGattServer = mBluetoothManager?.openGattServer(this#MainActivity,gattCallback)
mBluetoothGattServer?.connect(result.device,false)
val gattCallback = object: BluetoothGattServerCallback() {
override fun onConnectionStateChange(device: BluetoothDevice?, status: Int, newState: Int) {
super.onConnectionStateChange(device, status, newState)
if (newState == BluetoothProfile.STATE_CONNECTED) {
val service = BluetoothGattService(UUID.fromString("f000aa01-0451-4000-b000-000000000000"), BluetoothGattService.SERVICE_TYPE_PRIMARY)
val characteristic = BluetoothGattCharacteristic(UUID.fromString("00002a00-0000-1000-8000-00805f9b34fb"),
BluetoothGattCharacteristic.PROPERTY_READ or BluetoothGattCharacteristic.PROPERTY_WRITE or BluetoothGattCharacteristic.PROPERTY_NOTIFY,
BluetoothGattCharacteristic.PERMISSION_READ or BluetoothGattCharacteristic.PERMISSION_WRITE)
characteristic.addDescriptor(BluetoothGattDescriptor(UUID.fromString("00002902-0000-1000-8000-00805f9b34fb"), BluetoothGattCharacteristic.PERMISSION_WRITE))
service.addCharacteristic(characteristic)
mBluetoothGattServer?.addService(service)
}
}
// Not sure if this is needed but it never triggers.
override fun onCharacteristicWriteRequest(device: BluetoothDevice?, requestId: Int, characteristic: BluetoothGattCharacteristic?, preparedWrite: Boolean, responseNeeded: Boolean, offset: Int, value: ByteArray?) {
super.onCharacteristicWriteRequest(device, requestId, characteristic, preparedWrite, responseNeeded, offset, value)
mBluetoothGattServer?.sendResponse(device, requestId, BluetoothGatt.GATT_SUCCESS, offset, "Hello".toByteArray())
}

Receiving BluetoothGattCallback multiple times after foreground Service restart

I am working with BLE enabled hardware and communicating with the hardware using Foreground Service of the Android.
Foreground service is responsible for handling the BLE related events and it works quite good as per requirements for a while but somehow if the Foreground service is got killed or BLE connection is broken due to any reason then app tries to reconnect to the BLE again and then BLE callbacks start getting duplicate events from the BluetoothGattCallback, that is even though hardware sends a single event to Bluetooth but Android BluetoothGattCallback receives multiple callbacks for the same which leads to a lot of errors in our implementations.
For reference please go through Logs as follows,
Following are methods and callbacks from my foreground service,
BLEManagerService: *****onDescriptorWrite: 0*****<br>
BLEManagerService: *****onDescriptorWrite: 0*****<br>
BLEManagerService: *****onDescriptorWrite: 0*****<br>
BLEManagerService: Firmware: onCharacteristicRead true<br>
BLEManagerService: *****onDescriptorWrite: 0*****<br>
BLEManagerService: Firmware: onCharacteristicRead true<br>
BLEManagerService: *****onCharacteristicRead: 0*****<br>
BLEManagerService: *****onCharacteristicRead: 0*****<br>
override fun onCreate() {
super.onCreate()
mBluetoothGatt?.let { refreshDeviceCache(it) }
registerReceiver(btStateBroadcastReceiver, IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED))
}
/**
* Start BLE scan
*/
private fun scanLeDevice(enable: Boolean) {
if (enable && bleConnectionState == DISCONNECTED) {
//initialize scanning BLE
startScan()
scanTimer = scanTimer()
} else {
stopScan("scanLeDevice: (Enable: $enable)")
}
}
private fun scanTimer(): CountDownTimer {
return object : CountDownTimer(SCAN_PERIOD, 1000) {
override fun onTick(millisUntilFinished: Long) {
//Nothing to do
}
override fun onFinish() {
if (SCAN_PERIOD > 10000 && bleConnectionState == DISCONNECTED) {
stopScan("restart scanTimer")
Thread.sleep(200)
scanLeDevice(true)
SCAN_PERIOD -= 5000
if (null != scanTimer) {
scanTimer!!.cancel()
scanTimer = null
}
scanTimer = scanTimer()
} else {
stopScan("stop scanTimer")
SCAN_PERIOD = 60000
}
}
}
}
//Scan callbacks for more that LOLLIPOP versions
private val mScanCallback = object : ScanCallback() {
override fun onScanResult(callbackType: Int, result: ScanResult) {
val btDevice = result.device
if (null != btDevice) {
val scannedDeviceName: String? = btDevice.name
scannedDeviceName?.let {
if (it == mBluetoothFemurDeviceName) {
stopScan("ScanCallback: Found device")
//Disconnect from current connection if any
mBluetoothGatt?.let {it1 ->
it1.close()
mBluetoothGatt = null
}
connectToDevice(btDevice)
}
}
}
}
override fun onBatchScanResults(results: List<ScanResult>) {
//Not Required
}
override fun onScanFailed(errorCode: Int) {
Log.e(TAG, "*****onScanFailed->Error Code: $errorCode*****")
}
}
/**
* Connect to BLE device
* #param device
*/
fun connectToDevice(device: BluetoothDevice) {
scanLeDevice(false)// will stop after first device detection
//Stop Scanning before connect attempt
try {
if (null != scanTimer) {
scanTimer!!.cancel()
}
} catch (e: Exception) {
//Just handle exception if something
// goes wrong while canceling the scan timer
}
//Stop scan if still BLE scanner is running
stopScan("connectToDevice")
if (mBluetoothGatt == null) {
connectedDevice = device
if (Build.VERSION.SDK_INT >= 26)
connectedDevice?.connectGatt(this, false, mGattCallback)
}else{
disconnectDevice()
connectedDevice = device
connectedDevice?.connectGatt(this, false, mGattCallback)
}
}
/**
* Disconnect from BLE device
*/
private fun disconnectDevice() {
mBluetoothGatt?.close()
mBluetoothGatt = null
bleConnectionState = DISCONNECTED
mBluetoothManager = null
mBluetoothAdapter = null
mBluetoothFemurDeviceName = null
mBluetoothTibiaDeviceName = null
connectedDevice = null
}
/****************************************
* BLE Related Callbacks starts *
* Implements callback methods for GATT *
****************************************/
// Implements callback methods for GATT events that the app cares about. For example,
// connection change and services discovered.
private val mGattCallback = object : BluetoothGattCallback() {
/**
* Connection state changed callback
*/
override fun onConnectionStateChange(gatt: BluetoothGatt, status: Int, newState: Int) {
if (newState == BluetoothProfile.STATE_CONNECTED) {
mBluetoothGatt = gatt
//Stop Scanning before connect attempt
try {
if (null != scanTimer) {
scanTimer!!.cancel()
}
} catch (e: Exception) {
//Just handle exception if something
// goes wrong while canceling the scan timer
}
stopScan("onConnectionStateChange")// will stop after first device detection
} else if (newState == BluetoothProfile.STATE_DISCONNECTED || status == 8) {
disconnectDevice()
Handler(Looper.getMainLooper()).postDelayed({
initialize()
}, 500)
}
}
/**
* On services discovered
* #param gatt
* #param status
*/
override fun onServicesDiscovered(gatt: BluetoothGatt, status: Int) {
super.onServicesDiscovered(gatt, status)
}
override fun onDescriptorWrite(gatt: BluetoothGatt, descriptor: BluetoothGattDescriptor, status: Int) {
super.onDescriptorWrite(gatt, descriptor, status)
}
/**
* On characteristic read operation complete
* #param gatt
* #param characteristic
* #param status
*/
override fun onCharacteristicRead(gatt: BluetoothGatt, characteristic: BluetoothGattCharacteristic, status: Int) {
super.onCharacteristicRead(gatt, characteristic, status)
}
/**
* On characteristic write operation complete
* #param gatt
* #param characteristic
* #param status
*/
override fun onCharacteristicWrite(gatt: BluetoothGatt, characteristic: BluetoothGattCharacteristic, status: Int) {
super.onCharacteristicWrite(gatt, characteristic, status)
val data = characteristic.value
val dataHex = byteToHexStringJava(data)
}
/**
* On Notification/Data received from the characteristic
* #param gatt
* #param characteristic
*/
override fun onCharacteristicChanged(gatt: BluetoothGatt, characteristic: BluetoothGattCharacteristic) {
super.onCharacteristicChanged(gatt, characteristic)
val data = characteristic.value
val dataHex = byteToHexStringJava(data)
}
override fun onReadRemoteRssi(gatt: BluetoothGatt, rssi: Int, status: Int) {
super.onReadRemoteRssi(gatt, rssi, status)
val b = Bundle()
b.putInt(BT_RSSI_VALUE_READ, rssi)
receiver?.send(APP_RESULT_CODE_BT_RSSI, b)
}
}
/**
* Bluetooth state receiver to handle the ON/OFF states
*/
private val btStateBroadcastReceiver = object : BroadcastReceiver() {
override fun onReceive(context: Context, intent: Intent) {
val state = intent.getIntExtra(BluetoothAdapter.EXTRA_STATE, -1)
when (state) {
BluetoothAdapter.STATE_OFF -> {
//STATE OFF
}
BluetoothAdapter.STATE_ON -> {
//STATE ON
btState = BT_ON
val b = Bundle()
receiver?.send(APP_RESULT_CODE_BT_ON, b)
initialize()
}
BluetoothAdapter.STATE_TURNING_OFF -> {
//Not Required
}
BluetoothAdapter.STATE_TURNING_ON -> {
//Not Required
}
}
}
}
private fun handleBleDisconnectedState() {
mBluetoothGatt?.let {
it.close()
receiver?.send(DISCONNECTED, b)
Handler(Looper.getMainLooper()).postDelayed({
mBluetoothManager = null
mBluetoothAdapter = null
mBluetoothFemurDeviceName = null
mBluetoothTibiaDeviceName = null
mBluetoothGatt = null
}, 1000)
}
}
/****************************************
* BLE Related Callbacks End ***
****************************************/
/****************************************************
* Register Receivers to handle calbacks to UI ***
****************************************************/
override fun onDestroy() {
super.onDestroy()
try {
mBluetoothGatt?.let {
it.close()
mBluetoothGatt = null
}
unregisterReceivers()
scanTimer?.cancel()
} catch (e: Exception) {
e.printStackTrace()
}
}
override fun onTaskRemoved(rootIntent: Intent?) {
super.onTaskRemoved(rootIntent)
Log.e(TAG, "onTaskRemoved")
stopSelf()
}
/**
* Unregister the receivers before destroying the service
*/
private fun unregisterReceivers() {
unregisterReceiver(btStateBroadcastReceiver)
}
companion object {
private val TAG = BLEManagerService::class.java.simpleName
private var mBluetoothGatt: BluetoothGatt? = null
var bleConnectionState: Int = DISCONNECTED
}
}

Don't set mBluetoothGatt = gatt in onConnectionStateChange. Instead set it from the return value of connectGatt. Otherwise you might create multiple BluetoothGatt objects without closing previous ones and therefore get multiple callbacks.