add ability to control whether to show congestion levels on alternative route lines, update changelog

Author: ShanMa1991

CHANGELOG.md

@@ -26,6 +26,7 @@
 * Renamed public property `MBCongestionAttribute` to `CongestionAttribute`. ([#2808](https://github.com/mapbox/mapbox-navigation-ios/pull/2808))
 * `NavigationViewController.mapView` was renamed to `NavigationViewController.navigationMapView`. ([#2808](https://github.com/mapbox/mapbox-navigation-ios/pull/2808))
 * `NavigationMapView.highlightBuildings(at:in3D:)` was renamed to `NavigationMapView.highlightBuildings(at:in3D:completion:)`. ([#2827](https://github.com/mapbox/mapbox-navigation-ios/pull/2827))
+* Add ability to show congestion levels with different colors on alternative route lines, after receiving multiple routes in `RouteResponse`  if  `NavigationMapView.showsAlternativeCongestion`  is set to  `true`. ([#2887](https://github.com/mapbox/mapbox-navigation-ios/pull/2887))
 
 ### Location tracking
 

Example/ViewController.swift

@@ -57,6 +57,8 @@ class ViewController: UIViewController {
             }
 
             startButton.isEnabled = true
+            // Show congestion levels on alternative route lines if there're multiple routes in the response.
+            navigationMapView.showsAlternativeCongestion = true
             navigationMapView.show(routes)
             navigationMapView.showWaypoints(on: currentRoute)
         }

Sources/MapboxNavigation/NavigationMapView+VanishingRouteLine.swift

@@ -217,7 +217,7 @@ extension NavigationMapView {
         })
     }
 
-    func routeLineGradient(_ route: Route, fractionTraveled: Double, isMain: Bool) -> [Double: UIColor]? {
+    func routeLineGradient(_ route: Route, fractionTraveled: Double, isMain: Bool = true) -> [Double: UIColor]? {
         var gradientStops = [CGFloat: UIColor]()
 
         /**

Sources/MapboxNavigation/NavigationMapView.swift

@@ -55,6 +55,12 @@ open class NavigationMapView: UIView {
     public var roadClassesWithOverriddenCongestionLevels: Set<MapboxStreetsRoadClass>? = nil
 
     var cameraAnimator: CameraAnimator!
+    /**
+     Controls whether to show congestion levels on alternative route lines. Defaults to `false`.
+     
+     If `true` and there're multiple routes to choose, the alternative route lines would display the congestion levels at different colors, similar to the main route. To customize the congestion colors that represent different congestion levels, override the `alternativeTrafficUnknownColor` , `alternativeTrafficLowColor`, `alternativeTrafficModerateColor`, `alternativeTrafficHeavyColor`, `alternativeTrafficSevereColor` property for the `NavigationMapView.appearance()`.
+     */
+    public var showsAlternativeCongestion: Bool = false
 
     enum IdentifierType: Int {
         case source
@@ -558,7 +564,7 @@ open class NavigationMapView: UIView {
         lineLayer.layout?.lineJoin = .constant(.round)
         lineLayer.layout?.lineCap = .constant(.round)
 
-        if let gradientStops = routeLineGradient(route, fractionTraveled: fractionTraveledForStops, isMain: true) {
+        if let gradientStops = routeLineGradient(route, fractionTraveled: fractionTraveledForStops) {
             lineLayer.paint?.lineGradient = .expression((Expression.routeLineGradientExpression(gradientStops)))
         }
 
@@ -641,8 +647,10 @@ open class NavigationMapView: UIView {
         lineLayer.layout?.lineJoin = .constant(.round)
         lineLayer.layout?.lineCap = .constant(.round)
 
-        if let gradientStops = routeLineGradient(route, fractionTraveled: 0.0, isMain: false) {
-            lineLayer.paint?.lineGradient = .expression((Expression.routeLineGradientExpression(gradientStops)))
+        if showsAlternativeCongestion {
+            if let gradientStops = routeLineGradient(route, fractionTraveled: 0.0, isMain: false) {
+                lineLayer.paint?.lineGradient = .expression((Expression.routeLineGradientExpression(gradientStops)))
+            }
         }
         mapView.style.addLayer(layer: lineLayer, layerPosition: LayerPosition(below: parentLayerIndentifier))