Change radius to MKCircle on MKMapView with UISlider

Question

I'm trying to change the radius of MKCircle by moving an UISlider. The problem is that the radius property of MKCircle is readonly.

I tried in this way:

- (void)sliderValueChanged:(UISlider *)sender
{
    self.radiusLabel.text = [NSString stringWithFormat:@"%i mt", value];

    MKCircle * oldC = (MKCircle *)self.mapView.overlays[0];

    MKCircle * c = [MKCircle circleWithCenterCoordinate:self.lastLocation.coordinate radius:value];

    [self.mapView addOverlay:c];

    [self.mapView removeOverlay:oldC];
}

but the render is very slow and the circle is rendered tile-by-tile (like a pdf in quartz). Is there a better and faster way to change the radius ?

Thanks...

Answer 1

You might be interested in the answer to this question: moving/updating MKOverlay on MKMapView

basically, instead of removing your old circle and adding a new one, you adjust the current one and tell the mapview to redraw that area.