MKPolylineView not rendered on MKMapView till MKMapView is clicked - ios

Question

I have a view controller, where I initialize a mkmapview programatically, and set the view controller to be the delegate of mkmapview. Also, this mapview is added as a subview to scrollview in the view controller class.
I add a mkpolyline to mkmapview, and I have
- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id <MKOverlay>)overlay
However, viewforoverlay is not called when view controller is loaded, but it is called when I click/touch mapview and drag/move it around

Answer 1

This problem is typically seen if you add the MKOverlay to the MKMapView prior to assigning the delegate. When you add the MKOverlay to the MKMapView, the delegate method mapView:viewForOverlay: is called. If you have not assigned the delegate by that time, you will not see the overlay renderer in the initial render.

Answer 2

Try adding this line after you add your MKPolylineView overlay:
[myMapView setNeedsRedisplay];
This is how I add a route to my map:
-(void)drawRoute
{
...
routeLine = [MKPolyline polylineWithPoints:pointArr count:totalPoints];
[geoMap addOverlay:routeLine];
....
}
-(MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id<MKOverlay>)overlay
{
MKPolylineView *lineView = [[[MKPolylineView alloc] initWithPolyline:overlay] autorelease];
UIColor *lineColor = [[UIColor alloc] initWithRed:0 green:0 blue:0 alpha:1.0];
lineView.fillColor = lineColor;
lineView.strokeColor = lineColor;
[lineColor release];
lineView.lineWidth = 12;
lineView.alpha = 1;
return lineView;
}