MapKit Polyline custom zoom?

Question

I am trying to learn how to use a polyline to connect two points on a map in ios6. First off, I have read over every tutorial on this subject that a simple Google search turns up and can not get polylines to work for one reason. Every tutorial that I have seen always adds the polyline to the map and adjusts the zoom of the map to fit the whole line. How would I go about making and adding a polyline to a map in ios6 if I want the map to stay zoomed in at a constant distance and only show the end of the polyline if it is larger then the current view? For example say I had a polyline that was a mile long and wanted the map to stay zoomed in at a constand distacne equivelent to:

MKCoordinateRegion userRegion = MKCoordinateRegionMakeWithDistance(self.currentLocation.coordinate, 1000, 1000);
    [self.mainMap setRegion:[self.mainMap regionThatFits:userRegion] animated:YES];

How would I go about doing this? Please provide full code examples or a sample project that I could download!

Answer 1

MKMapPoint * malloc / assign:

MKMapPoint *newPoints = malloc((sizeof (MKMapPoint) * nbPoints));
newPoints[index] = varMKMapPoint;
free(newPoints);

MKPolyline must be initialize in your needed :

MKPolyline *polyline  = [MKPolyline polylineWithPoints:newPoints count:nbPoints];
[self.mapView addOverlay:polyline];

to display your MKPolyline, you have to use viewForOverlay :

- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id <MKOverlay>)overlay
{
    MKOverlayView* overlayView = [[MKOverlayView alloc] initWithOverlay:overlay];        
    if([overlay isKindOfClass:[MKPolyline class]]) {
        MKPolylineView *backgroundView = [[MKPolylineView alloc] initWithPolyline:overlay];
        backgroundView.fillColor = [UIColor blackColor];
        backgroundView.strokeColor = backgroundView.fillColor;
        backgroundView.lineWidth = 10;
        backgroundView.lineCap = kCGLineCapSquare;
        overlayView = backgroundView;
    }
    return overlayView;
}

To use this method, you have to convert your points to CLLocation, it will returns a MKCoordinateRegion that you will set to mapView :

- (MKCoordinateRegion)getCenterRegionFromPoints:(NSArray *)points
{
    CLLocationCoordinate2D topLeftCoordinate;
    topLeftCoordinate.latitude = -90;
    topLeftCoordinate.longitude = 180;
    CLLocationCoordinate2D bottomRightCoordinate;
    bottomRightCoordinate.latitude = 90;
    bottomRightCoordinate.longitude = -180;
    for (CLLocation *location in points) {
        topLeftCoordinate.longitude = fmin(topLeftCoordinate.longitude, location.coordinate.longitude);
        topLeftCoordinate.latitude = fmax(topLeftCoordinate.latitude, location.coordinate.latitude);
        bottomRightCoordinate.longitude = fmax(bottomRightCoordinate.longitude, location.coordinate.longitude);
        bottomRightCoordinate.latitude = fmin(bottomRightCoordinate.latitude, location.coordinate.latitude);
    }
    MKCoordinateRegion region;
    region.center.latitude = topLeftCoordinate.latitude - (topLeftCoordinate.latitude - bottomRightCoordinate.latitude) * 0.5;
    region.center.longitude = topLeftCoordinate.longitude + (bottomRightCoordinate.longitude - topLeftCoordinate.longitude) * 0.5;
    region.span.latitudeDelta = fabs(topLeftCoordinate.latitude - bottomRightCoordinate.latitude) * 1.2; //2
    region.span.longitudeDelta = fabs(bottomRightCoordinate.longitude - topLeftCoordinate.longitude) * 1.2; //2
//    NSLog(@"zoom lvl : %f, %f", region.span.latitudeDelta, region.span.latitudeDelta);
    return region;
}

Hope this helps.