I am having some trouble understanding how to add multiple overlays to MKMapView.
I have an array routes tracked. The routes tracked are arrays of CLLocations. So I have an array of arrays.
I am able to take one route and draw it on the map view. However, I need to draw ALL the routes onto the map view.
So here is how I go about creating the MKPolyline for 1 route:
-(void) loadRoute
{
//So we grab an array that holds all the locations of one route.
NSArray *locations = [[NSArray alloc] initWithArray:[routesArray objectAtIndex:0]];
// while we create the route points, we will also be calculating the bounding box of our route
// so we can easily zoom in on it.
MKMapPoint northEastPoint;
MKMapPoint southWestPoint;
// create a c array of points.
MKMapPoint* pointArr = malloc(sizeof(CLLocationCoordinate2D) *[locations count]);
for(int idx = 0; idx < [locations count]; idx++)
{
CLLocation *tempLoc = (CLLocation*)[locations objectAtIndex:idx];
CLLocationDegrees latitude = tempLoc.coordinate.latitude;
CLLocationDegrees longitude = tempLoc.coordinate.longitude;
// create our coordinate and add it to the correct spot in the array
CLLocationCoordinate2D coordinate = CLLocationCoordinate2DMake(latitude, longitude);
MKMapPoint point = MKMapPointForCoordinate(coordinate);
// if it is the first point, just use them, since we have nothing to compare to yet.
if (idx == 0) {
northEastPoint = point;
southWestPoint = point;
}
else
{
if (point.x > northEastPoint.x)
northEastPoint.x = point.x;
if(point.y > northEastPoint.y)
northEastPoint.y = point.y;
if (point.x < southWestPoint.x)
southWestPoint.x = point.x;
if (point.y < southWestPoint.y)
southWestPoint.y = point.y;
}
pointArr[idx] = point;
}
self.routeLine = [MKPolyline polylineWithPoints:pointArr count:[locations count]];
//Zoom in to fit route on screen
_routeRect = MKMapRectMake(southWestPoint.x, southWestPoint.y, northEastPoint.x - southWestPoint.x, northEastPoint.y - southWestPoint.y);
// clear the memory allocated earlier for the points
free(pointArr);
}
Here is the MapKit delegate call that returns the overlay:
#pragma mark MKMapViewDelegate
- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id <MKOverlay>)overlay
{
MKOverlayView* overlayView = nil;
if(overlay == self.routeLine)
{
//if we have not yet created an overlay view for this overlay, create it now.
if(nil == self.routeLineView)
{
self.routeLineView = [[MKPolylineView alloc] initWithPolyline:self.routeLine];
self.routeLineView.fillColor = [UIColor redColor];
self.routeLineView.strokeColor = [UIColor redColor];
self.routeLineView.lineWidth = 3;
}
overlayView = self.routeLineView;
}
return overlayView;
}
So all the code given above works fine. I can't figure out how to load more overlays to show the other routes.
I thought that maybe in loadRoute method, running through all the routes and creating a MKOverlayView for each one. Storing all those MKOverlayView in an array then doing: [self.mapView addOverlays:array];
But it doesn't work. The problem is that in the delegate method I somehow need to know which overlay to return.
So if I could do something along the lines of:
- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id <MKOverlay>)overlay
{
int tag = overlay.tag;
return (MKOverlayView*)[arrayOfViews objectAtIndex:tag];
}
it would work fine. But unfortunately it doesn't work like that :(
Any help would be very much appreciated!
EDIT:
I use this in ViewDidLoad to add the overlay:
[self loadRoute];
// add the overlay to the map
if (nil != self.routeLine) {
[self.mapView addOverlay:self.routeLine];
}
// zoom in on the route.
[self zoomInOnRoute];
This is in the header:
// the data representing the route points.
MKPolyline* _routeLine;
// the view we create for the line on the map
MKPolylineView* _routeLineView;
// the rect that bounds the loaded points
MKMapRect _routeRect;
The routeLine and routeLineView variables can only point to one overlay and overlay view at a time so you would theoretically need an array of such variables.
However, based on the code shown, you don't need to keep references to these in the first place.
I suggest removing the routeLine and routeLineView variables.
Then you just create an overlay object locally and in viewForOverlay return a view for the requested overlay parameter.
In the loadRoute method, you can loop through the routesArray and for each route, create a local overlay object, and call addOverlay on it.
There's also an easier way to construct a map rect that bounds all the routes so you can set the map's region to show them all.
Example:
-(void) loadRoute
{
_routeRect = MKMapRectNull;
for (int raIndex = 0; raIndex < routesArray.count; raIndex++)
{
//So we grab an array that holds all the locations of one route.
NSArray *locations = [[NSArray alloc] initWithArray:
[routesArray objectAtIndex:raIndex]];
//note we are getting object at raIndex (not 0) above
//...no change to existing code here...
//self.routeLine = [MKPolyline polylineWithPoints:pointArr count:[locations count]];
//replace above line with this...
MKPolyline *pl = [MKPolyline polylineWithPoints:pointArr count:[locations count]];
[mapView addOverlay:pl];
//Zoom in to fit route on screen
//_routeRect = MKMapRectMake(southWestPoint.x, southWestPoint.y, northEastPoint.x - southWestPoint.x, northEastPoint.y - southWestPoint.y);
//replace above line with this to create a rect around ALL routes...
if (MKMapRectIsNull(_routeRect))
_routeRect = pl.boundingMapRect;
else
_routeRect = MKMapRectUnion(_routeRect, pl.boundingMapRect);
// clear the memory allocated earlier for the points
free(pointArr);
}
}
In viewDidLoad, just call loadRoute and don't call addOverlay.
The viewForOverlay method becomes much simpler:
- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id <MKOverlay>)overlay
{
MKPolylineView *pv = [[MKPolylineView alloc] initWithPolyline:overlay];
pv.fillColor = [UIColor redColor];
pv.strokeColor = [UIColor redColor];
pv.lineWidth = 3;
return pv;
}
By the way, in loadRoute, this line:
MKMapPoint* pointArr = malloc(sizeof(CLLocationCoordinate2D) *[locations count]);
should be:
MKMapPoint* pointArr = malloc(sizeof(MKMapPoint) *[locations count]);
It should use the size of MKMapPoint (not CLLocationCoordinate2D).
They are not the same thing (even though the structs happen to be the same byte size).