如何计算适合MKCircle的MKMapView缩放级别？

Question

我想要在按钮单击事件时显示mkcircle。我必须使用圆半径来计算MKMapView的缩放级别，以使圆noticeable.Let半径可以小或大，但mkmapview上的mkcircle应该足够大，如screenshot.My代码中所示：

- (IBAction)showCircle:(id)sender {
    long radius=[self calculateRadius];
    NSLog(@"draw circle of radius=%ld",radius);
    MKCircle *circle= [[MKCircle alloc]init];
    circle = [MKCircle circleWithCenterCoordinate:CLLocationCoordinate2DMake([groupLat floatValue], [groupLon floatValue]) radius:radius];
    [myMapView addOverlay:circle];
    MKCoordinateRegion region = MKCoordinateRegionMakeWithDistance(CLLocationCoordinate2DMake([groupLat floatValue], [groupLon floatValue]), 800, 800);

    //calculate zoom level
    double radius = [circle radius] + [circle radius] / 2;
    double scale = radius / 500;
    zoomLevel=(16 - log(scale) / log(2));

    region.span.latitudeDelta  =zoomLevel;
    region.span.longitudeDelta =zoomLevel;

    [myMapView setRegion:region animated:YES];

//问题是圆看起来很小，外面的空间更多

​

我想要如下输出

​

​

如有任何建议，我们将不胜感激。谢谢!

Answer 1

我知道它的老帖子，但不管怎样，回复..Swift 5中的代码，Xcode 11

let region = MKCoordinateRegion(circle.boundingMapRect)
mapView.setRegion(region, animated: true)

或者，我们可以通过以下方式轻松地添加一些保证金

mapView.setVisibleMapRect(circle.boundingMapRect, edgePadding: UIEdgeInsets(top: 50, left: 50, bottom: 50, right: 50), animated: true)