MKPolyline的问题

Question

I am very new to Xcode and I am facing issues in tracing user path using polyline.

I am getting locations correctly. I am able to add pins properly. However, my polyline method is never called.

Below is my code.

In header file...

@interface Tracker : UIViewController <MKMapViewDelegate, CLLocationManagerDelegate>
{
    MKMapView *mapView;
    //other declarations
}

Inside implementation file, I have following code. I call, drawPolyline method inside didUpdateLocations method, which is called correctly.

- (void) drawPolyline:(NSArray *)locations
{
    NSInteger numberOfLocations = [locations count];
    if (numberOfLocations > 1)
    {
        CLLocationCoordinate2D *locationCoordinate2DArray = malloc(numberOfLocations * sizeof(CLLocationCoordinate2D));
        for (int i = 0; i < numberOfLocations; i++)
        {
            CLLocation* current = [locations objectAtIndex:i];
            locationCoordinate2DArray[i] = current.coordinate;
        }

        self.polyline = [MKPolyline polylineWithCoordinates:locationCoordinate2DArray count:numberOfLocations];
        free(locationCoordinate2DArray);

        [mapView addOverlay:self.polyline];
        [mapView setNeedsDisplay];
    }
}

- (MKOverlayView*)mapView:(MKMapView*)mapView viewForOverlay:(id <MKOverlay>)overlay
{
    MKPolylineView* polyLineView = [[MKPolylineView alloc] initWithPolyline:self.polyline];
    polyLineView.strokeColor = [UIColor blueColor];
    polyLineView.lineWidth = 2;
    return polyLineView;
}

Your help is highly appreciated. Thanks in advance.

Answer 1

mapView:viewForOverlay: is a delegate method, so you'll need to set the mapview's delegate somewhere. Otherwise, the delegate method will never be called.

[mapView setDelegate:self];