Detect touch nearby to CLLocationCoordinate2D in pixels - ios

Question

I have few GMSMarker on GMSMapView, all of them are draggable, so when I longpress them, I can move them around the map. However I have also an action on longpress on GMSMapView, which adds a marker.
- (void)mapView:(GMSMapView *)mapView didBeginDraggingMarker:(GMSMarker *)marker {
self.moving = YES;
}
- (void)mapView:(GMSMapView *)mapView didEndDraggingMarker:(GMSMarker *)marker {
self.moving = NO;
}
- (void)mapView:(GMSMapView *)mapView didLongPressAtCoordinate:(CLLocationCoordinate2D)coordinate {
if (self.moving) {
return;
}
[self addMarkerAtCoordinate:coordinate];
}
Now the problem is, that sometimes user mistap and instead of moving marker he adds a new one. Because of this, I'd like to add small area around marker, where user can't add new markers. I've thought about something like this:
- (void)mapView:(GMSMapView *)mapView didLongPressAtCoordinate:(CLLocationCoordinate2D)coordinate {
CGFloat zoomFactor = 35.f - self.mapView.camera.zoom;
CLLocation *location = [[CLLocation alloc] initWithLatitude:coordinate.latitude longitude:coordinate.longitude];
for (GMSMarker *marker in self.markers) {
CLLocation *sectorLocation = [[CLLocation alloc] initWithLatitude:marker.position.latitude longitude:marker.position.longitude];
if ([location distanceFromLocation:sectorLocation] < zoomFactor) {
return;
}
}
}
But of course I don't like this solution, because the area is changing with changed zoom. I'd like something like a finger width around marker to be longpress banned. How to calculate this distance?

Answer 1

It's easy to convert coordinate to location on view using method pointForCoordinate: on GMSProjection GMSMapView object.
- (void)mapView:(GMSMapView *)mapView didLongPressAtCoordinate:(CLLocationCoordinate2D)coordinate {
CGPoint longpressPoint = [mapView.projection pointForCoordinate:coordinate];
for (GMSMarker *marker in self.markers) {
CLLocationCoordinate2D markerCoordinate = marker.position;
CGPoint sectorPoint = [mapView.projection pointForCoordinate:markerCoordinate];
if (fabsf(longpressPoint.x - markerCoordinate.x) < 30.f && fabsf(longpressPoint.y - markerCoordinate.y) < 30.f) { // 30.f ofc should be defined as constant
// handle situation when touchpoint is too close to marker
}
}
}