Bluetooth LE scanner observable

rx-ble-scanner.kt

import android.bluetooth.BluetoothAdapter
import android.bluetooth.BluetoothDevice
import io.reactivex.Observable
import java.util.concurrent.TimeUnit

data class BLEScanResult(val dev: BluetoothDevice,
                         val rssi: Int,
                         val scanRecord: ByteArray)

fun rxBLEScanner(btAdapter: BluetoothAdapter,
                 duration: Long = 0,
                 timeUnit: TimeUnit = TimeUnit.SECONDS) = {
  var scancb: BluetoothAdapter.LeScanCallback? = null
  Observable.create<BLEScanResult> {emi ->
    scancb = BluetoothAdapter.LeScanCallback{dev, rssi, rec -> emi.onNext(BLEScanResult(dev, rssi, rec))}
    btAdapter.startLeScan(scancb)
    if (duration > 0) Observable.timer(duration, timeUnit).subscribe{emi.onComplete()}
  }.doFinally{btAdapter.stopLeScan(scancb)}
}()