MKMapView overlay does not display on map - objective-c

Question

My app gets the points for a route from google. The response also contains the bounding rect. My app creates the rect and shows the map correctly and I add the overlay. The
- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id <MKOverlay>)
overlay is called and I construct a MKOverlayPathView from the points. I have verified that the points are within the bounding rect. However, the route overlay does not draw on the displayed map.
I have checked everything I can think of with no joy, any suggestions would be greatly appreciated.

Answer 1

I don't know yet why the overlay isn't showing but try the following code in a fresh, new project.
In my test, I added the map view control to the xib and then connected the IBOutlet and the map view's delegate outlet to File's Owner. Creating the map view in code will also work (just don't also add it to the xib and be sure to set the delegate property).
This is my test TRTrip class:
//TRTrip.h...
#interface TRTrip : NSObject<MKOverlay>
#property (nonatomic, readonly) MKMapRect boundingMapRect;
#property (nonatomic, readonly) CLLocationCoordinate2D coordinate;
#end
//TRTrip.m...
#implementation TRTrip
#synthesize boundingMapRect;
#synthesize coordinate;
-(MKMapRect)boundingMapRect {
return MKMapRectWorld;
}
-(CLLocationCoordinate2D)coordinate {
return CLLocationCoordinate2DMake(42.3507,-71.0608);
}
#end
In the view controller's viewDidLoad, I add an MKPointAnnotation, MKCircle, TRTrip, and an MKPolyline to the map:
- (void)viewDidLoad
{
[super viewDidLoad];
CLLocationCoordinate2D bostonCoord = CLLocationCoordinate2DMake(42.3507,-71.0608);
//center map on Boston...
mMapView.region = MKCoordinateRegionMakeWithDistance(bostonCoord, 30000, 30000);
//add boston annotation...
MKPointAnnotation *pa = [[MKPointAnnotation alloc] init];
pa.coordinate = bostonCoord;
pa.title = #"Boston";
[mMapView addAnnotation:pa];
[pa release];
//add MKCircle overlay...
MKCircle *circle = [MKCircle circleWithCenterCoordinate:bostonCoord radius:10000];
[mMapView addOverlay:circle];
//add TRTrip overlay...
TRTrip *trt = [[TRTrip alloc] init];
[mMapView addOverlay:trt];
[trt release];
//NOTE:
//Using an MKPolyline and MKPolylineView is probably easier than
//manually drawing lines using MKOverlayPathView.
//add MKPolyline overlay...
int numberOfRouteCoords = 3;
CLLocationCoordinate2D *routeCoords = malloc(numberOfRouteCoords * sizeof(CLLocationCoordinate2D));
routeCoords[0] = CLLocationCoordinate2DMake(42.34, -71.1);
routeCoords[1] = CLLocationCoordinate2DMake(42.25, -71.05);
routeCoords[2] = CLLocationCoordinate2DMake(42.3, -71.02);
MKPolyline *pl = [MKPolyline polylineWithCoordinates:routeCoords count:numberOfRouteCoords];
[mMapView addOverlay:pl];
free(routeCoords);
}
and this is the viewForOverlay method:
-(MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id<MKOverlay>)overlay
{
if ([overlay isKindOfClass:[MKCircle class]])
{
MKCircleView *cv = [[[MKCircleView alloc] initWithCircle:overlay] autorelease];
cv.fillColor = [UIColor greenColor];
cv.strokeColor = [UIColor blueColor];
cv.alpha = 0.5;
return cv;
}
if ([overlay isKindOfClass:[TRTrip class]])
{
MKOverlayPathView *opv = [[[MKOverlayPathView alloc] initWithOverlay:overlay] autorelease];
opv.strokeColor = [UIColor redColor];
opv.lineWidth = 3;
CGMutablePathRef myPath = CGPathCreateMutable();
MKMapPoint mp1 = MKMapPointForCoordinate(CLLocationCoordinate2DMake(42.3507,-71.1));
CGPoint cgp1 = [opv pointForMapPoint:mp1];
CGPathMoveToPoint(myPath, nil, cgp1.x, cgp1.y);
MKMapPoint mp2 = MKMapPointForCoordinate(CLLocationCoordinate2DMake(42.45,-71.05));
CGPoint cgp2 = [opv pointForMapPoint:mp2];
CGPathAddLineToPoint(myPath, nil, cgp2.x, cgp2.y);
MKMapPoint mp3 = MKMapPointForCoordinate(CLLocationCoordinate2DMake(42.3,-71.0));
CGPoint cgp3 = [opv pointForMapPoint:mp3];
CGPathAddLineToPoint(myPath, nil, cgp3.x, cgp3.y);
opv.path = myPath;
CGPathRelease(myPath);
return opv;
}
if ([overlay isKindOfClass:[MKPolyline class]])
{
MKPolylineView *plv = [[[MKPolylineView alloc] initWithPolyline:overlay] autorelease];
plv.strokeColor = [UIColor purpleColor];
plv.lineWidth = 5;
return plv;
}
return nil;
}
Here is the result:
The red line on top is the TRTrip and the purple one on the bottom is the MKPolyline.

Answer 2

If your example is a bit more complex then this, check if you have any calls like this:
[mMapView removeOverlay:overlay]
in the code.