iOS - MKOverlayView custom view rect fills works, but line draws do not

Question

New to Map Overlays, but this is a really weird problem.

I pass in the mapView.visibleMapRect to my overlay implementation and return that as the boundingMapRect, which is fine for now - just trying to draw a line on the whole map rect.

My drawMapRect is getting called, and in the following code - the partially transparent green rectangle is drawn, but the lines are not. I've verified the line drawing code in drawRect of a uiview subclass, so I know it draws something :-)

I'm sure I must be missing something easy, but I can't see it :-)

The thing that throws me off is that the visibleMapRect, when converted to a CGRect has very strange coordinates - they don't look like screen coordinates to me at all - which seems like the source of the problem to me.

Any help would be greatly appreciated:

The drawMapRect is called multiple times, i'm attaching the output below.

Thanks, Bob

ViewController setup code:

CLLocationCoordinate2D center;
center.latitude = 29.46;
center.longitude = -98.30;

MKCoordinateRegion region;

MKCoordinateSpan span;
span.latitudeDelta = 0.2;
span.longitudeDelta = 0.2;

region.center = center;
region.span = span;

self.mapView.region = region;

MyOverlay *myoverlay = [[MyOverlay alloc] initWithCoordinate: center andBoundingRect: self.mapView.visibleMapRect];
[self.mapView addOverlay:myoverlay];

MyOverlay code:

@implementation MyOverlay

@synthesize coordinate;
@synthesize boundingMapRect;


- (id) initWithCoordinate: (CLLocationCoordinate2D) coord andBoundingRect: (MKMapRect) bRect {

    if ((self = [super init])) {
        //customize here

        coordinate = coord;
        boundingMapRect = bRect;
    }

    return self;

}

MyOverlayView drawing code

- (void)drawMapRect:(MKMapRect)mapRect zoomScale:(MKZoomScale)zoomScale inContext:(CGContextRef)context {

    CGRect theRect = [self rectForMapRect:mapRect];

    NSLog(@"in drawMapRect ...theRect is %f, %f, size of %f x %f", theRect.origin.x, theRect.origin.y, theRect.size.width, theRect.size.height); 
    CGContextSetAlpha(context, 1.0);
    CGContextSetStrokeColorWithColor(context, [UIColor blueColor].CGColor);
    CGContextMoveToPoint(context, theRect.origin.x, theRect.origin.y);
    CGContextAddLineToPoint(context, theRect.size.width, theRect.size.width);

    CGContextSetAlpha(context, .25);
    CGContextSetFillColorWithColor(context, [UIColor greenColor].CGColor);
    CGContextFillRect(context, theRect);

}

Output

2011-05-16 11:25:18.037 coolOverlayTest[71661:7903] in drawMapRect ...theRect is 61440.000000, 37888.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.038 coolOverlayTest[71661:760b] in drawMapRect ...theRect is 323584.000000, 37888.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.042 coolOverlayTest[71661:7903] in drawMapRect ...theRect is 323584.000000, 37888.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.044 coolOverlayTest[71661:760b] in drawMapRect ...theRect is -200704.000000, 37888.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.046 coolOverlayTest[71661:7903] in drawMapRect ...theRect is -200704.000000, 37888.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.048 coolOverlayTest[71661:760b] in drawMapRect ...theRect is 61440.000000, -224256.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.052 coolOverlayTest[71661:760b] in drawMapRect ...theRect is 323584.000000, -224256.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.054 coolOverlayTest[71661:7903] in drawMapRect ...theRect is 323584.000000, -224256.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.056 coolOverlayTest[71661:760b] in drawMapRect ...theRect is -200704.000000, -224256.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.057 coolOverlayTest[71661:7903] in drawMapRect ...theRect is -200704.000000, -224256.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.059 coolOverlayTest[71661:760b] in drawMapRect ...theRect is 61440.000000, 300032.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.061 coolOverlayTest[71661:7903] in drawMapRect ...theRect is 61440.000000, 300032.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.063 coolOverlayTest[71661:760b] in drawMapRect ...theRect is 323584.000000, 300032.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.064 coolOverlayTest[71661:7903] in drawMapRect ...theRect is 323584.000000, 300032.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.066 coolOverlayTest[71661:760b] in drawMapRect ...theRect is -200704.000000, 300032.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.068 coolOverlayTest[71661:7903] in drawMapRect ...theRect is -200704.000000, 300032.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.070 coolOverlayTest[71661:760b] in drawMapRect ...theRect is 585728.000000, 37888.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.072 coolOverlayTest[71661:7903] in drawMapRect ...theRect is 585728.000000, 37888.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.074 coolOverlayTest[71661:760b] in drawMapRect ...theRect is -462848.000000, 37888.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.075 coolOverlayTest[71661:7903] in drawMapRect ...theRect is -462848.000000, 37888.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.082 coolOverlayTest[71661:7903] in drawMapRect ...theRect is 61440.000000, -486400.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.082 coolOverlayTest[71661:760b] in drawMapRect ...theRect is 585728.000000, -224256.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.085 coolOverlayTest[71661:760b] in drawMapRect ...theRect is 61440.000000, -486400.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.087 coolOverlayTest[71661:7903] in drawMapRect ...theRect is -462848.000000, -224256.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.089 coolOverlayTest[71661:760b] in drawMapRect ...theRect is -462848.000000, -224256.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.099 coolOverlayTest[71661:760b] in drawMapRect ...theRect is 585728.000000, 300032.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.102 coolOverlayTest[71661:760b] in drawMapRect ...theRect is -462848.000000, 300032.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.106 coolOverlayTest[71661:760b] in drawMapRect ...theRect is 323584.000000, -486400.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.109 coolOverlayTest[71661:760b] in drawMapRect ...theRect is -200704.000000, -486400.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.111 coolOverlayTest[71661:7903] in drawMapRect ...theRect is -200704.000000, -486400.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.116 coolOverlayTest[71661:760b] in drawMapRect ...theRect is 585728.000000, -486400.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.119 coolOverlayTest[71661:7903] in drawMapRect ...theRect is 585728.000000, -486400.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.124 coolOverlayTest[71661:7903] in drawMapRect ...theRect is -462848.000000, -486400.000000, size of 262144.000000 x 262144.000000
2011-05-16 11:25:18.126 coolOverlayTest[71661:760b] in drawMapRect ...theRect is -462848.000000, -486400.000000, size of 262144.000000 x 262144.000000

score 4 · Answer 1 · answered Dec 12 '12 at 19:58

One thing to consider is that for performance reasons, drawMapRect: is called on multiple threads. This explains why you see drawMapRect: getting called multiple times. Additionally the mapRect input to this method is NOT necessarily equal to the visible mapView.visibleMapRect. In fact mapRect is usually a small section of mapView.visibleMapRect and different threads render different regions of mapView.visibleMapRect. Thus just because a point is contained inside mapView.visibleMapRect it does not mean that it is contained within the mapRect passed to all of the resulting calls to drawMapRect.

score 0 · Answer 2 · answered Jan 15 '13 at 22:35

You have the wrong coordinates in your call to CGContextAddLineToPoint. You have:

CGContextMoveToPoint(context, theRect.origin.x, theRect.origin.y);
CGContextAddLineToPoint(context, theRect.size.width, theRect.size.width);

but it should be:

CGContextMoveToPoint(context, theRect.origin.x, theRect.origin.y);
CGContextAddLineToPoint(context, theRect.origin.x + theRect.size.width, theRect.origin.y + theRect.size.height);

At least if you are hoping to draw a line diagonally across your rectangle.

Also as Ludvik Polak mentioned above, you probably also need to set the line width using something like:

CGContextSetLineWidth(context, MKRoadWidthAtZoomScale(zoomScale));

score 0 · Answer 3 · answered Dec 29 '22 at 23:21

0

I have come across this when there is another MKTileOverlay loading on the same map. It will cause the custom overlay to refresh until a tile is drawn by the other overlay, which may take several seconds in case of network load.

answered Dec 29 '22 at 23:21

piotros

23
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iOS - MKOverlayView custom view rect fills works, but line draws do not

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