CODEWITHSUNDEEP
swiftmkmapviewcoordinatespolyline
George
George

Reputation: 189

Plotting Co-ordinates with MKMapView using Polyline (Swift)

I am trying to use MKMapView to plot pre-determined coordinates on a map. The following code is triggered by a button.

The array 'coordinatesArr' is 2D, and contains latitude, longitude, and a timestamp. Each element is stored as a string for other reasons, and therefore co-ordinates are converted to Doubles when loaded.

Example:

 [["37.33027293", "-122.02788965", "2018-05-30 15:18:21.459808+0100"], ["37.33026014", "-122.02768476", "2018-05-30 15:18:22.459808+0100"]]

The code is held within the following class:

 class PostCell: UITableViewCell, MKMapViewDelegate

Code

 (MAP IS THE FOLLOWING OUTLET: @IBOutlet weak var activityFeedMap: MKMapView!)

 let span = MKCoordinateSpanMake(0.001, 0.001)
 // ALTHOUGH THIS WILL NOT BE MY ULTIMATE METHOD, THE MAP IS CURRENTLY CENTRED ON THE FIRST LOCATION
 let myLocation = CLLocationCoordinate2DMake(Double(coordinatesArr[0][1]) ?? 0.0, Double(coordinatesArr[0][0])!)
 let region = MKCoordinateRegionMake(myLocation, span)
 activityFeedMap.setRegion(region, animated:true)
 activityFeedMap.delegate=self
 activityFeedMap.mapType = MKMapType.hybrid

 // CODE IN QUESTION
 // ---
 // PERHAPS I SHOULD LOOP THROUGH THE ARRAY, BUT I BELIEVE THIS
 // FULFILS THE SAME PURPOSE
 var counter=0
 while counter < (coordinatesArr.count - 1){

    // LASTLOCFORMATTED, AND NEXTLOCFORMATTED ARE EACH A SET OF
    // CO-ORDINATES BETWEEN WHICH A POLYLINE SHOULD BE PLOTTED
    let lastLocFormatted = CLLocationCoordinate2DMake(Double(coordinatesArr[counter][1])!, Double(coordinatesArr[counter][0])!)

    let nextLocFormatted = CLLocationCoordinate2DMake(Double(coordinatesArr[counter+1][1])!, Double(coordinatesArr[counter+1][0])!)

    // AN ARRAY HOLDING THE CO-ORDINATES OF THE POINTS TO PLOT
    // A POLYLINE BETWEEN
    var a=[lastLocFormatted, nextLocFormatted]

    // LINE TO PLOT
    let polyline = MKPolyline(coordinates: &a, count: counter)

    activityFeedMap.add(polyline)

    COUNTER += 1
 }


func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
    // CHECK TO SEE WHETHER OVERLAY IS OF TYPE MKPOLYLINE
    // AND ONLY LAY TRACE IF TIMER RUNNING
    // note: different renderer required for differnt types
    if overlay is MKPolyline{
        // CREATE MKPOLYLINERENDERER AND PASS OUR OVERLAY OVER
        let polylineRenderer = MKPolylineRenderer(overlay: overlay)
        // SET LINE COLOR TO BLUE
        polylineRenderer.strokeColor = UIColor.orange
        // SET LINE WIDTH TO 4
        polylineRenderer.lineWidth = 4
        return polylineRenderer
    }
    // IF OVERLAY NOT OF TYPE MKPOLYLINE
    return MKPolylineRenderer()
}

Although this code is partly working, I am gaining extra data somehow. 

 37.33027293, -122.02788965
 37.33026634, -122.0278357
 37.33026525, -122.02778504
 37.33026222, -122.02773507
 37.33026014, -122.02768476

The above should plot:

enter image description here

This code creates the following, however

enter image description here

The line outlined in blue appears to continue on indefinitely.

Any help that you can provide would be greatly appreciated, as I am new to Swift and have exhausted all rectifying actions I can think of.

Thanks!

Upvotes: 0

Views: 167

Answers (1)

Joshua Smith
Joshua Smith

Reputation: 6621

First off, I'd recommend using https://developer.apple.com/documentation/mapkit/mkpolyline/1452773-polylinewithpoints poloylineWithPoints instead of adding a polyline for each one.

What it looks like is your overshooting and your last segment is zooming off to Zero Island.

Upvotes: 1

Related Questions