title: Resizing MKCircle on MKMapView is flickering
body: <p>I'm trying to solve a problem since few days and I've got no good results. I've got a point and a circle on <code>MKMapView</code>. I've got <code>UISlider</code> and want to change size of <code>MKCircle</code>. Size is changed but during resizing this circle flickers and blinks.</p>
  
  <p>Here is my code:</p>
  
  <pre><code>@implementation ViewController {
      Annotation *_annotation;
  }
  
  - (void)viewDidLoad
  {
      [super viewDidLoad];
      _annotation = [[Annotation alloc] init];
      [_annotation setCoordinate: CLLocationCoordinate2DMake(0, 0)];
      [self.mapView addAnnotation:_annotation];
      [self.mapView setCenterCoordinate:_annotation.coordinate animated:YES];
  
      MKCoordinateRegion region = MKCoordinateRegionMakeWithDistance(_annotation.coordinate, 1000, 1000);
      [self.mapView setRegion:region];
  
      [self _addCircleOnCurrentLocationWithRadius:_slider.value];
  }
  
  - (IBAction)onSliderChanged:(UISlider *)sender {
      [self.mapView removeOverlays:self.mapView.overlays];
      [self _addCircleOnCurrentLocationWithRadius:sender.value];
  }
  
  - (void)_addCircleOnCurrentLocationWithRadius:(CGFloat)radius {
      MKCircle *circle = [MKCircle circleWithCenterCoordinate:_annotation.coordinate radius:radius];
      [self.mapView addOverlay:circle level:MKOverlayLevelAboveRoads];
  }
  
  #pragma mark - MKMapViewDelegate
  - (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id&lt;MKAnnotation&gt;)annotation {
      MKPinAnnotationView *view = [[MKPinAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:@"Annotation"];
      return view;
  }
  
  - (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id&lt;MKOverlay&gt;)overlay {
      MKCircleView *view = [[MKCircleView alloc] initWithCircle:overlay];
      view.fillColor = [UIColor redColor];
      view.strokeColor = [UIColor blueColor];
      view.alpha = 0.3;
      return view;
  }
  
  @end
  </code></pre>
  
  <p>I've tried:</p>
  
  <ul>
  <li>removing old overlays and adding new one,</li>
  <li>doing as above with <code>NSOperationQueue</code></li>
  </ul>
  
  <p>Here is <a href="https://dl.dropboxusercontent.com/u/11493275/stackoverflow/flickering.mov" rel="nofollow noreferrer">a screen recording how it looks like</a>.</p>
  
  <p>I see that is possible to do, Apple did this in Reminders app.</p>
  
  <p>Also I'm familiar with following topics:</p>
  
  <ul>
  <li><a href="https://stackoverflow.com/questions/17571332/smooth-resizing-of-mkcircle">Smooth resizing of MKCircle</a></li>
  <li><a href="https://stackoverflow.com/questions/22441059/moving-mkcircle-on-mkmapview-and-dragging-mkmapview">Moving MKCircle on MKMapview and dragging MKMapview</a></li>
  <li><a href="http://www.coderexception.com/CmbNBH63UyxyUXXP/smooth-resizing-of-mkcircle" rel="nofollow noreferrer">Smooth resizing of MKCircle</a></li>
  </ul>
  
  <p>Thank you in advance.</p>
  
  <p><strong>Edit</strong>
  I've did it. I will add an answer with class which supports resizing today or tomorrow. </p>