Android Activity for Obtaining BLE Transmission Power

MainActivity.kt

class MainActivity : AppCompatActivity() {
    var bluetoothAdapter : BluetoothAdapter? = null
    var bluetoothScanner : BluetoothLeScanner? = null
    
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        rssiTextView = findViewById(R.id.rssiTextView)

        bluetoothAdapter = BluetoothAdapter.getDefaultAdapter()
        bluetoothScanner = bluetoothAdapter?.getBluetoothLeScanner()
        bluetoothScanner?.startScan(scanCallback);
    }

    /*
     The scanResult is represented as an array of integers.
     The first 2 bytes are the protocol
     The 16 following bytes are the UUID
     The 2 after that your major
     The 2 after that your minor
     The final bytes are your tx power / reference RSSI.
     */
    val scanCallback = object: ScanCallback(){
        @RequiresApi(Build.VERSION_CODES.O)
        override fun onScanResult(callbackType: Int, result: ScanResult) {
            //224 is the official bluetooth google company identifier.
            val manufacturerSpecificData = result.scanRecord.getManufacturerSpecificData(224)
            val rssi = result.rssi.toDouble() //The intensity of the received signal
            val tx = result.txPower.toDouble() //The power of the broadcast (Available on Oreo only)
            val distance = calculateDistance(tx,rssi)
        }
    }

    fun calculateDistance(txPower: Double, rssi: Double): Double {
        val ratio = rssi / txPower
        if (rssi == 0.0) { // Cannot determine accuracy, return -1.
            return -1.0
        } else if (ratio < 1.0) { //default ratio
            return Math.pow(ratio, 10.0)
        }//rssi is greater than transmission strength
        return (0.89976) * Math.pow(ratio, 7.7095) + 0.111
    }
}