write text in drawRect MKPolygonRenderer

问题

Ok I'm at my wits end. I'm new to MapKit and writing a health stats app that plots data on a MKMapView relative to where patients live. I can drop annotations, and draw polygons of postcode areas with no problem.

However I'd like to write text on the map polygon (and not an annotation).

Here's my code, I've subclassed MKPolygonRender to access drawRect.

Polygons are perfect but no text. I've tried write to the first point in the polygon (I will find centre eventually)

Been stuck for several nights so really grateful.

class PolygonRender: MKPolygonRenderer { var point:CGPoint!

override init(overlay: MKOverlay) {
    super.init(overlay: overlay)
}

override func drawMapRect(mapRect: MKMapRect, zoomScale: MKZoomScale, inContext context: CGContext) {


    super.drawMapRect(mapRect, zoomScale: zoomScale, inContext: context)
    let mapRect:MKMapRect = self.overlay.boundingMapRect
    let rect:CGRect = self.rectForMapRect(mapRect)
    UIGraphicsPushContext(context)
    var bPath = UIBezierPath()
    //let polygon:MKPolygon = self.polygon
    super.fillColor = UIColor.yellowColor()
    let points = self.polygon.points()
    let pointCount = self.polygon.pointCount

    var point:CGPoint = self.pointForMapPoint(points[0])
    bPath.moveToPoint(point)

    for var i = 1; i < pointCount; i++ {
        point = self.pointForMapPoint(points[i])
        bPath.addLineToPoint(point)

    }
    bPath.closePath()
    bPath.addClip()

    let roadWidth:CGFloat = MKRoadWidthAtZoomScale(zoomScale)

    let attributes: [String: AnyObject] = [
        NSForegroundColorAttributeName : UIColor.blackColor(),
        NSFontAttributeName : UIFont.systemFontOfSize(5 * roadWidth)]


    let centerPoint = pointForMapPoint(points[0])
    print(centerPoint)
    let string:NSString = "Hello world"
    string.drawAtPoint(centerPoint, withAttributes: attributes)




    UIGraphicsPopContext()
}

回答1:

Generally you do it right but I think the font size is too small to see the text.

Try to set font size to value like 100 or bigger to find out the text is there, but you will need to zoom in.

Example:

public override func draw(_ mapRect: MKMapRect, zoomScale: MKZoomScale, in context: CGContext) {

    let rect:CGRect = self.rect(for: mapRect)

    UIGraphicsPushContext(context);

    // ...

    UIGraphicsPushContext(context);
    UIColor.black.setStroke()
    context.setLineWidth(1)
    context.stroke(rect.insetBy(dx: 0.5, dy: 0.5))

    let paragraphStyle = NSMutableParagraphStyle()
    paragraphStyle.alignment = .center

    let attributes = [NSAttributedStringKey.paragraphStyle  : paragraphStyle,
                      NSAttributedStringKey.font            : UIFont.systemFont(ofSize: 100.0),
                      NSAttributedStringKey.foregroundColor : UIColor.black]
    "\(rect.size)".draw(in: rect, withAttributes: attributes)
    UIGraphicsPopContext();
}

Image below shows how on the map is displayed text with font size 100 when the rect size is 1024x1024

来源：https://stackoverflow.com/questions/35492876/write-text-in-drawrect-mkpolygonrenderer

标签

swift

text

mapkit

mkpolygonrenderer