如何在iOS地图上叠加圆圈

Question

我有一个半径和一个位置。

这就是我试图获取圆的边界矩形的方法。

- (MKMapRect)boundingMapRect{

    CLLocationCoordinate2D tmp;
    MKCoordinateSpan radiusSpan = MKCoordinateRegionMakeWithDistance(self.coordinate, 0, self.radius).span;
    tmp.latitude = self.coordinate.latitude - radiusSpan.longitudeDelta;
    tmp.longitude = self.coordinate.longitude - radiusSpanSpan.longitudeDelta;

    MKMapPoint upperLeft = MKMapPointForCoordinate(tmp);
    MKMapRect bounds = MKMapRectMake(upperLeft.x, upperLeft.y, self.radius * 2, self.radius * 2);

    return bounds;
}

MKMapRectMake(...)似乎想要在地图点测量宽度和高度。如何将半径转换为？

最后我将它渲染成这样：

MKMapRect theMapRect = [self.overlay boundingMapRect];
CGRect theRect = [self rectForMapRect:theMapRect];
CGContextAddEllipseInRect(ctx, theRect);
CGContextFillPath(ctx);

最后，地图上的半径似乎不等于米，也似乎没有正确测量距离。怎么做对了？

我会非常感谢每一个提示。

Answer 1

你应该使用MKCircle。做类似的事情：

CLLocationDistance fenceDistance = 300;
CLLocationCoordinate2D circleMiddlePoint = CLLocationCoordinate2DMake(yourLocation.latitude, yourLocation.longitude);
MKCircle *circle = [MKCircle circleWithCenterCoordinate:circleMiddlePoint radius:fenceDistance];
[yourMapView addOverlay: circle];

并采用下面的MKMapViewDelegate方法并执行以下操作：

- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id<MKOverlay>)overlay

{
     MKCircleView *circleView = [[[MKCircleView alloc] initWithCircle:(MKCircle *)overlay] autorelease];
     circleView.fillColor = [[UIColor redColor] colorWithAlphaComponent:0.9];
     return circleView;
 }

Answer 2

对于iOS7：

与viewDidLoad中的tdevoy相同：

CLLocationDistance fenceDistance = 300;
CLLocationCoordinate2D circleMiddlePoint = CLLocationCoordinate2DMake(yourLocation.latitude, yourLocation.longitude);
MKCircle *circle = [MKCircle circleWithCenterCoordinate:circleMiddlePoint radius:fenceDistance];
[yourMapView addOverlay: circle];

但委托方法（因为mapView：viewForOverlay：已弃用）：

- (MKOverlayRenderer *)mapView:(MKMapView *)mapView rendererForOverlay:(id < MKOverlay >)overlay
{
    MKCircleRenderer *circleR = [[MKCircleRenderer alloc] initWithCircle:(MKCircle *)overlay];
    circleR.fillColor = [UIColor greenColor];

    return circleR;
}