gatt callback

gattCallbackClient.kt

val gattCallBack = object : BluetoothGattCallback() {
            override fun onConnectionStateChange(gatt: BluetoothGatt, status: Int, newState: Int) {
                super.onConnectionStateChange(gatt, status, newState)
                val isSuccess = status == BluetoothGatt.GATT_SUCCESS
                val isConnected = newState == BluetoothProfile.STATE_CONNECTED
                if (isSuccess && isConnected) {
                    // Discover the service on the server on are connected on
                    gatt.discoverServices()
                }
            }

            override fun onServicesDiscovered(discoveredGatt: BluetoothGatt, status: Int) {
                super.onServicesDiscovered(discoveredGatt, status)
                if (status == BluetoothGatt.GATT_SUCCESS) {
                    val characteristic = discoveredGatt.getService(SERVICE_UUID).getCharacteristic(MESSAGE_UUID)
                    // Send a message to the watch 
                    characteristic.value = "your message".toByteArray(Charsets.UTF_8)
                    val result = discoveredGatt.writeCharacteristic(characteristic)
                    
                    if (result) {
                        // Manage the result
                    }
                }
            }
        }