I have an app which polls a remote server by sending to it its cache GPS location. Sometimes a remote server will ask for live location and an app must send it to it.

object MyLocationManager {
    val providers = listOf(
        LocationManager.GPS_PROVIDER,
        "fused",
        LocationManager.NETWORK_PROVIDER,
        LocationManager.PASSIVE_PROVIDER,
    )


    fun getCached(ctx: Context, locationManager: LocationManager): Location? {
        for (provider in providers) {
            when (provider) {
                "fused" -> {
                    val fusedLocationClient =
                        LocationServices.getFusedLocationProviderClient(ctx)
                    val fusedLocationTask = fusedLocationClient.lastLocation
                    val fusedLocation = getTaskResult(fusedLocationTask)
                    if (fusedLocation != null) {
                        return fusedLocation
                    }
                }
                else -> {
                    if (locationManager.isProviderEnabled(provider)) {
                        val lastKnownLocation = locationManager.getLastKnownLocation(provider)
                        Log.d(
                            TAG,
                            "Provider: $provider, Last Known Location: $lastKnownLocation"
                        )

                        if (lastKnownLocation != null) {
                            return lastKnownLocation
                        }
                    }
                }
            }
        }

        return null
    }

    fun getLive(ctx: Context, locationManager: LocationManager): Location? {
        val locationListener = object : LocationListener {
            override fun onLocationChanged(location: Location) {

                //This works correctly!
                //
                //1) how to save its result? How to save it into cache?
                //2) or how to return it from here?
                Log.d(TAG, "onLocationChanged: ${location.latitude}, ${location.longitude}")

                stopLocationUpdates()
            }

            private fun stopLocationUpdates() {
                val fusedLocationClient = LocationServices.getFusedLocationProviderClient(ctx)

                try {
                    // Stop location updates
                    fusedLocationClient.removeLocationUpdates(locationCallback)
                    Log.d(TAG, "Location updates stopped")
                } catch (e: SecurityException) {
                    Log.e(TAG, "SecurityException while stopping location updates: ${e.message}")
                }
            }

            private val locationCallback = object : LocationCallback() {
                override fun onLocationResult(locationResult: LocationResult) {
                    super.onLocationResult(locationResult)
                    val location = locationResult.lastLocation
                    if (location != null) {
                        onLocationChanged(location)
                    } else {
                        Log.e(TAG, "Received null location in onLocationResult")
                    }
                }
            }
        }

        for (provider in providers) {
            when (provider) {
                LocationManager.GPS_PROVIDER -> {

                    //obsolete, in the last Android versions
                    val _locationRequest = LocationRequest.create()
                        .setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY)
                        .setInterval(0)
                        .setFastestInterval(0)

                    val fusedLocationClient = LocationServices.getFusedLocationProviderClient(ctx)
                    val locationResult: Task = fusedLocationClient.getLocationAvailability()

                    if (!Tasks.await(locationResult).isLocationAvailable) {
                        return null
                    }

                    val locationTask: Task = fusedLocationClient.getCurrentLocation(
                        LocationRequest.PRIORITY_HIGH_ACCURACY,
                        null
                    )

                    return Tasks.await(locationTask)
                }

                "fused" -> {
                    val apiAvailability = GoogleApiAvailability.getInstance()
                    val resultCode = apiAvailability.isGooglePlayServicesAvailable(ctx)

                    if (resultCode == ConnectionResult.SUCCESS) {
                        val fusedLocationClient = LocationServices.getFusedLocationProviderClient(ctx)
                        val fusedLocationTask = fusedLocationClient.lastLocation
                        val fusedLocation = getTaskResult(fusedLocationTask)
                        if (fusedLocation != null) {
                            return fusedLocation
                        }
                    } else {
                        Log.w(TAG, " Google Play Services aren't available, can't use fused")
                    }

                }

                else -> {
                    if (locationManager.isProviderEnabled(provider)) {
                        locationManager.requestSingleUpdate(
                            provider,
                            locationListener,
                            Looper.getMainLooper()
                        )

                        val lastKnownLocation = locationManager.getLastKnownLocation(provider)
                        if (lastKnownLocation != null) {
                            return lastKnownLocation
                        }
                    }
                }
            }
        }

        return null
    }
}

An issue is that the code for obtaining GPS location doesn't work properly. Firstly, I don't know whether the approach in the code is correct. Secondly, I don't know how to properly to return the GPS coordinates from a callback -- see the comments. Thirdly, I don't know how to force it to store the latest coordinates that it's obtained into cache.

And there're some functions that's been derprecated in the latest versions of Android, particularly in Android 10.

How to do all of this?

My device is rooted.