Offline navigation with Mapbox Sdk in Android app from Kml

Question

I'm trying to develop an offline navigation app for Trekking.

The app shows to the user a list of nearby track/routes where he can go. Examples:
-Walking to Etna Vulcan
-Walking in the wood.

I've several KML files provided to me by local guides, each one for a different track.

So, if i choose "Walking to Etna Vulcan", I will have a Map with the track that I've to follow to go the Etna Vulcan, with some markers of interesting point (Examples: Refuges, Monuments). This data is actually ready, in KML format.

So: The user chooses the track from the list that I provide, then the phone shows the track on the map(from kml or equivalent) with the current user position.

I'm doing it with MapBox sdk (but i'm open to alternatives).

Actually, I've successfully downloaded an offline map of the zone (Sicily), but i'm note sure how to write my kml on the map.

I also imported a kml in Mapbox Studio, but i don't know how to download a MapBox Studio Map into my application.

Thank you for your time!

Answer 1

If Mapbox seems like a good alternative then you just need to study their Android SDK to see if and how drawing markers and coordinate tracks are supported.

For the tracks see https://www.mapbox.com/android-sdk/geojson/

The relevant (to you) part is right at the end of their example code:

LatLng[] pointsArray = points.toArray(new LatLng[points.size()]);

// Draw Points on MapView
mapboxMap.addPolyline(new PolylineOptions()
                    .add(pointsArray)
                    .color(Color.parseColor("#3bb2d0"))
                    .width(2));

Here they have the coordinate points in the points ArrayList. They have been extracted from GeoJSON data, but you would just need to extract the coordinate points from the KML data and then draw the track based on that example.

For markers see https://www.mapbox.com/android-sdk/marker/

They have this example code:

mapboxMap.addMarker(new MarkerOptions()
                    .position(new LatLng(48.13863, 11.57603))
                    .title("Hello World!")
                    .snippet("Welcome to my marker."));

For a marker with a custom icon see https://www.mapbox.com/android-sdk/custom-marker-icon/

They have this example code:

// Create an Icon object for the marker to use
IconFactory iconFactory = IconFactory.getInstance(MainActivity.this);
Drawable iconDrawable = ContextCompat.getDrawable(MainActivity.this, drawable.ic_directions_boat_black_18dp);
Icon icon = iconFactory.fromDrawable(iconDrawable);

// Add the custom icon marker to the map
mapboxMap.addMarker(new MarkerOptions()
                    .position(new LatLng(-33.8500000, 18.4158234))
                    .title("Cape Town Harbour")
                    .icon(icon));

So you would just use a regular Android Drawable for the custom icon.

Looks quite convenient. I haven't used the Mapbox SDK myself.