Start Mapbox Navigation UI using MapboxNavigation object

I successfully start Mapbox navigation UI using this line of code:

NavigationLauncher.startNavigation(MainActivity.this, options);

But I want to start a navigation session using a MapboxNavigation object so that I can implement listeners EG: the OffRouteListener.

To do so I use the following code, but no navigation UI shows up.

I'm not even sure that MapboxNavigation#startNavigation is supposed to start any visual component.

MapboxNavigation mapboxNavigation = new MapboxNavigation(MainActivity.this, accessToken, mapboxNavigationOptions);
mapboxNavigation.addOffRouteListener(location -> {
   // do things
});
mapboxNavigation.startNavigation(directionsRoute);

Solution

This example in the Mapbox Android documentation shows how to start a visual navigation component using MapboxNavigation#startNavigation, in conjunction with an OffRouteListener. The relevant section of the source code (also linked here) is:

@OnClick(R.id.startRouteButton)
public void onStartRouteClick() {
  boolean isValidNavigation = navigation != null;
  boolean isValidRoute = route != null && route.distance() > TWENTY_FIVE_METERS;
  if (isValidNavigation && isValidRoute) {

    // Hide the start button
    startRouteButton.setVisibility(View.INVISIBLE);

    // Attach all of our navigation listeners.
    navigation.addNavigationEventListener(this);
    navigation.addProgressChangeListener(this);
    navigation.addMilestoneEventListener(this);
    navigation.addOffRouteListener(this);

    ((ReplayRouteLocationEngine) locationEngine).assign(route);
    navigation.setLocationEngine(locationEngine);
    mapboxMap.getLocationComponent().setLocationComponentEnabled(true);
    navigation.startNavigation(route);
      mapboxMap.removeOnMapClickListener(this);
  }
}

The navigation variable is initialized here as an instance of MapboxNavigation.

So, adding the lines

((ReplayRouteLocationEngine) locationEngine).assign(route);
mapboxNavigation.setLocationEngine(locationEngine);
mapboxMap.getLocationComponent().setLocationComponentEnabled(true);

Before calling mapboxNavigation.startNavigation(directionsRoute); in your implementation should do the trick. You should also ensure that the directionsRoute object is a correctly formulated instance of the DirectionsRoute class.