Q:

Darkening the MKMapView's background color without darkening the MKOverlay

How would one darken the MKMapView's background color, and NOT darken the MKOverlay in the MKMapView's at the same time -- similar to the map view in the Nike+ app.

A:

OK , I got the solution here ,before add other overlays to the map ,you can add a total overlay as a background to the map ,so the map's background color is changed ,but the overlay is still as they are before ,here are codes
MKMapRect worldRect = MKMapRectWorld;
    MKMapPoint point1 = MKMapRectWorld.origin;
    MKMapPoint point2 = MKMapPointMake(point1.x+worldRect.size.width,point1.y);
    MKMapPoint point3 = MKMapPointMake(point2.x, point2.y+worldRect.size.height);
    MKMapPoint point4 = MKMapPointMake(point1.x, point3.y);

    MKMapPoint points[4] = {point1,point2,point3,point4};
    self.polygon = [MKPolygon polygonWithPoints:points count:4];
    [self.runMapView addOverlay:self.polygon];

