Problem with CLGeocoder.ReverseGeocodeLocationAsync in Xamarin - ios

Question

I am currently looking into (existing) solution for iOS under Xamarin. I have a map with following code:
public override async Task<string> ResolveLatLngToAddress(double lat, double lng, MapAddressFormat addressFormat)
{
var geocoder = new CLGeocoder();
try
{
var placemarks = await geocoder.ReverseGeocodeLocationAsync(new CLLocation(lat, lng));
if (placemarks.Length > 0)
{
var placemark = placemarks[0];
switch (addressFormat)
{
case MapAddressFormat.AddressFormatFull:
{
return FormatUtils.Join(true, placemark.Name, placemark.Locality, placemark.SubLocality);
}
case MapAddressFormat.AddressFormatNoNumber:
{
return FormatUtils.Join(true, placemark.Thoroughfare, placemark.Locality, placemark.SubLocality);
}
}
}
}
catch (Foundation.NSErrorException e)
{
// Unable to find a location with the supplied latitude and longitude
}
return null;
}
}
The code works really well when user moves the pin around, there is a textbox control that displays currently selected address. Once the user starts zooming in and out however, the application breaks and the function stops working.
I have done some research and I understand that CLGeocoder class works in a way that if the users starts too many requests, the response slows down and then stops completely (https://developer.apple.com/documentation/corelocation/clgeocoder).
I can see that the problem is that the event is triggered multiple times during the zoom, e.g. zooming in triggers for example 20 requests for location resolution.
I would to trigger the location resolution only after the user finished zooming, is it possible to achieve somehow, for example with delayed binding?
Please note that I am new to both iOS development and Xamarin.
Thank you very much for any help.

Answer 1

thank you for your comments. I have eventually solved it by caching previously queried location and re-querying only if the lat/lng coordinates changed by certain margin which I estimated to be 1 meter (perfectly fine for my purposes).
private double _cached_lat = 999;
private double _cached_lng = 9999;
private string _cached_location = "";
public override async Task<string> ResolveLatLngToAddress(double lat, double lng, MapAddressFormat addressFormat)
{
double latDif = System.Math.Abs(_cached_lat - lat);
double lngDif = System.Math.Abs(_cached_lng - lng);
//precission - around 1m
double geo_precission = 0.000005;
if (((System.Math.Abs (_cached_lat - lat) < geo_precission) && (System.Math.Abs (_cached_lng - lng) < geo_precission)) && (!string.IsNullOrEmpty(_cached_location)))
{
return _cached_location;
}
var geocoder = new CLGeocoder();