MapLibreParticleLab/platform/ios/MapLibre.docc/AnimatedLineExample.md

# Animated Line

Add an animated line to a map

> Note: This example uses UIKit.

Demonstrates using ``MLNPolyline/polylineWithCoordinates:count:`` to update an ``MLNPolyline``.


<!-- include-example(AnimatedLineExample) -->

```swift
class AnimatedLineExample: UIViewController, MLNMapViewDelegate {
    var mapView: MLNMapView!
    var timer: Timer?
    var polylineSource: MLNShapeSource?
    var currentIndex = 1
    var allCoordinates: [CLLocationCoordinate2D]!

    override func viewDidLoad() {
        super.viewDidLoad()

        mapView = MLNMapView(frame: view.bounds, styleURL: AMERICANA_STYLE)
        mapView.autoresizingMask = [.flexibleWidth, .flexibleHeight]

        mapView.setCenter(
            CLLocationCoordinate2D(latitude: 45.5076, longitude: -122.6736),
            zoomLevel: 11,
            animated: false
        )
        view.addSubview(mapView)

        mapView.delegate = self

        allCoordinates = coordinates
    }

    // Wait until the map is loaded before adding to the map.
    func mapViewDidFinishLoadingMap(_ mapView: MLNMapView) {
        addPolyline(to: mapView.style!)
        animatePolyline()
    }

    func addPolyline(to style: MLNStyle) {
        // Add an empty MLNShapeSource, we’ll keep a reference to this and add points to this later.
        let source = MLNShapeSource(identifier: "polyline", shape: nil, options: nil)
        style.addSource(source)
        polylineSource = source

        // Add a layer to style our polyline.
        let layer = MLNLineStyleLayer(identifier: "polyline", source: source)
        layer.lineJoin = NSExpression(forConstantValue: "round")
        layer.lineCap = NSExpression(forConstantValue: "round")
        layer.lineColor = NSExpression(forConstantValue: UIColor.blue)

        // The line width should gradually increase based on the zoom level.
        layer.lineWidth = NSExpression(forMLNInterpolating: NSExpression.zoomLevelVariable, curveType: MLNExpressionInterpolationMode.linear, parameters: nil, stops: NSExpression(forConstantValue: [14: 5, 18: 20]))
        style.addLayer(layer)
    }

    func animatePolyline() {
        currentIndex = 1

        // Start a timer that will simulate adding points to our polyline. This could also represent coordinates being added to our polyline from another source, such as a CLLocationManagerDelegate.
        timer = Timer.scheduledTimer(timeInterval: 0.05, target: self, selector: #selector(tick), userInfo: nil, repeats: true)
    }

    @objc func tick() {
        if currentIndex > allCoordinates.count {
            timer?.invalidate()
            timer = nil
            return
        }

        // Create a subarray of locations up to the current index.
        let coordinates = Array(allCoordinates[0 ..< currentIndex])

        // Update our MLNShapeSource with the current locations.
        updatePolylineWithCoordinates(coordinates: coordinates)

        currentIndex += 1
    }

    func updatePolylineWithCoordinates(coordinates: [CLLocationCoordinate2D]) {
        var mutableCoordinates = coordinates

        let polyline = MLNPolylineFeature(coordinates: &mutableCoordinates, count: UInt(mutableCoordinates.count))

        // Updating the MLNShapeSource’s shape will have the map redraw our polyline with the current coordinates.
        polylineSource?.shape = polyline
    }

    let coordinates = [
        (-122.63748, 45.52214),
        (-122.64855, 45.52218),
        (-122.6545, 45.52219),
        (-122.65497, 45.52196),
        (-122.65631, 45.52104),
        (-122.6578, 45.51935),
        (-122.65867, 45.51848),
        (-122.65872, 45.51293),
        (-122.66576, 45.51295),
        (-122.66745, 45.51252),
        (-122.66813, 45.51244),
        (-122.67359, 45.51385),
        (-122.67415, 45.51406),
        (-122.67481, 45.51484),
        (-122.676, 45.51532),
        (-122.68106, 45.51668),
        (-122.68503, 45.50934),
        (-122.68546, 45.50858),
        (-122.6852, 45.50783),
        (-122.68424, 45.50714),
        (-122.68433, 45.50585),
        (-122.68429, 45.50521),
        (-122.68456, 45.50445),
        (-122.68538, 45.50371),
        (-122.68653, 45.50311),
        (-122.68731, 45.50292),
        (-122.68742, 45.50253),
        (-122.6867, 45.50239),
        (-122.68545, 45.5026),
        (-122.68407, 45.50294),
        (-122.68357, 45.50271),
        (-122.68236, 45.50055),
        (-122.68233, 45.49994),
        (-122.68267, 45.49955),
        (-122.68257, 45.49919),
        (-122.68376, 45.49842),
        (-122.68428, 45.49821),
        (-122.68573, 45.49798),
        (-122.68923, 45.49805),
        (-122.68926, 45.49857),
        (-122.68814, 45.49911),
        (-122.68865, 45.49921),
        (-122.6897, 45.49905),
        (-122.69346, 45.49917),
        (-122.69404, 45.49902),
        (-122.69438, 45.49796),
        (-122.69504, 45.49697),
        (-122.69624, 45.49661),
        (-122.69781, 45.4955),
        (-122.69803, 45.49517),
        (-122.69711, 45.49508),
        (-122.69688, 45.4948),
        (-122.69744, 45.49368),
        (-122.69702, 45.49311),
        (-122.69665, 45.49294),
        (-122.69788, 45.49212),
        (-122.69771, 45.49264),
        (-122.69835, 45.49332),
        (-122.7007, 45.49334),
        (-122.70167, 45.49358),
        (-122.70215, 45.49401),
        (-122.70229, 45.49439),
        (-122.70185, 45.49566),
        (-122.70215, 45.49635),
        (-122.70346, 45.49674),
        (-122.70517, 45.49758),
        (-122.70614, 45.49736),
        (-122.70663, 45.49736),
        (-122.70807, 45.49767),
        (-122.70807, 45.49798),
        (-122.70717, 45.49798),
        (-122.70713, 45.4984),
        (-122.70774, 45.49893),
    ].map { CLLocationCoordinate2D(latitude: $0.1, longitude: $0.0) }
}
```

![](AnimatedLineExample.gif)

This map uses data from OpenStreetMap, the style uses OpenMapTiles.