我如何使用覆盖层在ios地图中绘制一条线

Question

我想使用覆盖层在ios地图上画一条线。我有一个代码在地图上绘制一条线。但这对我不起作用。谁能帮我。

MKCoordinateSpan span;     span.latitudeDelta = 0.03;     span.longitudeDelta = 0.03;

MKCoordinateRegion region;
region.span=span;
region.center=CLLocationCoordinate2DMake(39.046259, -76.851195);

[_myMapView setRegion:region animated:YES];
[_myMapView regionThatFits:region];

UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(singleTapWebView:)];
singleTap.numberOfTapsRequired = 1;
singleTap.delegate = self;
[self.myMapView addGestureRecognizer:singleTap];
[singleTap release];

CLLocationCoordinate2D commuterLotCoords[5]=
{
    CLLocationCoordinate2DMake(39.036399,-76.872208)
};
 MKPolygon *commuterParkingPolygon=[MKPolygon polygonWithCoordinates:commuterLotCoords count:5];
    [_myMapView addOverlay:commuterParkingPolygon];

在上面的代码中，我们可以从这一行改变终点“ CLLocationCoordinate2DMake（39.036399，-76.872208 ）”但总是起点是 lat 0.000003，长0.000000。我怎样才能改变起始品脱。任何人都可以帮我解决这个问题。