ios中MKOverlay的使用方法

Question

（MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id)overlay{}

以上FUNCTION应该如何使用，不知道怎么才有作用？

Answer 1

第一步： 在didLoadView中加入： 

MKCircle* circle = [MKCircle circleWithCenterCoordinate:newloc radius:5000]; 
[mapView addOverlay:circle];

 第二步：

(MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id )overlay
{ 
    if ([overlay isKindOfClass:[MKCircle class]]) 
    {
        MKCircleView* circleView = [[[MKCircleView alloc] initWithOverlay:overlay] autorelease]; 
        circleView.fillColor = [[UIColor cyanColor] colorWithAlphaComponent:0.2];
        circleView.strokeColor = [[UIColor blueColor] colorWithAlphaComponent:0.7];
        circleView.lineWidth = 3.0; return circleView; 
    }
    return nil; 
}