onRouteAlternatives
Invoked whenever available alternative routes to the destination change.
This callback is invoked whenever new alternatives are available (addition to the list), or when a fork between an alternative and the current primary route has been passed (removal from the list).
The alternatives list always represent all available, up-to-date, alternatives for the current route.
The alternatives are not automatically added to MapboxNavigation, you need to add them manually to trigger RoutesObserver, for example:
private val alternativesObserver = object : NavigationRouteAlternativesObserver {
override fun onRouteAlternatives(
routeProgress: RouteProgress,
alternatives: List<NavigationRoute>,
routerOrigin: RouterOrigin
) {
val newRoutes = mutableListOf<NavigationRoute>().apply {
add(mapboxNavigation.getNavigationRoutes().first())
addAll(alternatives)
}
mapboxNavigation.setNavigationRoutes(newRoutes, mapboxNavigation.currentLegIndex())
}
override fun onRouteAlternativesError(error: RouteAlternativesError) {
// error handling
}
}
mapboxNavigation.registerRouteAlternativesObserver(alternativesObserver)Please note that the example above doesn't properly handle offline-online route switching. Consider it as a basic example for demonstration purpose.
You can filter the alternatives out before setting them back to MapboxNavigation based on requirements.
Additionally, you can use the alternatives observer to switch to an offboard route if the current route was built onboard which can be used to always prefer an offboard-generated route over onboard-generated one. This is a good practice because offboard-generated routes take live road conditions into account, have more precise ETAs, and can also be refreshed as the user drives and conditions change. Example usage:
private val alternativesObserver = object : NavigationRouteAlternativesObserver {
override fun onRouteAlternatives(
routeProgress: RouteProgress,
alternatives: List<NavigationRoute>,
routerOrigin: RouterOrigin
) {
val primaryRoute = routeProgress.navigationRoute
val isPrimaryRouteOffboard = primaryRoute.origin == RouterOrigin.Offboard
val offboardAlternatives = alternatives.filter { it.origin == RouterOrigin.Offboard }
when {
isPrimaryRouteOffboard -> {
// if the current route is offboard, keep it
// but consider accepting additional offboard alternatives only and ignore onboard ones
val updatedRoutes = mutableListOf<NavigationRoute>()
updatedRoutes.add(primaryRoute)
updatedRoutes.addAll(offboardAlternatives)
mapboxNavigation.setNavigationRoutes(updatedRoutes, mapboxNavigation.currentLegIndex())
}
isPrimaryRouteOffboard.not() && offboardAlternatives.isNotEmpty() -> {
// if the current route is onboard, and there's an offboard route available
// consider notifying the user that a more accurate route is available and whether they'd want to switch
// or force the switch like presented
mapboxNavigation.setNavigationRoutes(offboardAlternatives)
}
else -> {
// in other cases, when current route is onboard and there are no offboard alternatives,
// just append the new alternatives
val updatedRoutes = mutableListOf<NavigationRoute>()
updatedRoutes.add(primaryRoute)
updatedRoutes.addAll(alternatives)
mapboxNavigation.setNavigationRoutes(updatedRoutes, mapboxNavigation.currentLegIndex())
}
}
}
override fun onRouteAlternativesError(error: RouteAlternativesError) {
// error handling
}
}
mapboxNavigation.registerRouteAlternativesObserver(alternativesObserver)Parameters
the current route's progress.
list of alternative routes, can be empty.
reports the source of all the new alternative routes in the list. If there are no new routes, reports the source that returned the latest additions.