Map Matching | Java SDK | Android Docs

Note

This example is a part of the Mapbox Android Demo app. You can find the values for all referenced resources in the res directory. For example, see res/values/activity_strings.xml for R.string.* references used in this example.

Map Matching API pricing

Products used within the Mapbox Java SDK, including the Map Matching API, are individually billed. For pricing information, see the documentation for the Map Matching API.

activity_javaservices_map_matching

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<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:mapbox="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".examples.javaservices.MapMatchingActivity">

    <com.mapbox.mapboxsdk.maps.MapView
        android:id="@+id/mapView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        mapbox:mapbox_cameraTargetLat="34.01591350351023"
        mapbox:mapbox_cameraTargetLng="-118.4945560781314"
        mapbox:mapbox_cameraZoom="14.5"/>

</LinearLayout>

MapMatchingActivity.java

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package com.mapbox.mapboxandroiddemo.examples.javaservices;

import android.graphics.Color;
import android.os.AsyncTask;
import android.os.Bundle;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

import com.mapbox.api.matching.v5.MapboxMapMatching;
import com.mapbox.api.matching.v5.models.MapMatchingMatching;
import com.mapbox.api.matching.v5.models.MapMatchingResponse;
import com.mapbox.core.exceptions.ServicesException;
import com.mapbox.geojson.Feature;
import com.mapbox.geojson.FeatureCollection;
import com.mapbox.geojson.LineString;
import com.mapbox.geojson.Point;
import com.mapbox.mapboxandroiddemo.R;
import com.mapbox.mapboxsdk.Mapbox;
import com.mapbox.mapboxsdk.maps.MapView;
import com.mapbox.mapboxsdk.maps.MapboxMap;
import com.mapbox.mapboxsdk.maps.OnMapReadyCallback;
import com.mapbox.mapboxsdk.maps.Style;
import com.mapbox.mapboxsdk.style.layers.LineLayer;
import com.mapbox.mapboxsdk.style.sources.GeoJsonSource;
import com.mapbox.mapboxsdk.utils.ColorUtils;

import java.io.InputStream;
import java.lang.ref.WeakReference;
import java.util.List;
import java.util.Objects;
import java.util.Scanner;

import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;
import timber.log.Timber;

import static com.mapbox.api.directions.v5.DirectionsCriteria.PROFILE_DRIVING;
import static com.mapbox.core.constants.Constants.PRECISION_6;
import static com.mapbox.mapboxsdk.style.layers.PropertyFactory.lineColor;
import static com.mapbox.mapboxsdk.style.layers.PropertyFactory.lineOpacity;
import static com.mapbox.mapboxsdk.style.layers.PropertyFactory.lineWidth;

/**
 * Match raw GPS points to the map so they align with roads and pathways.
 */
public class MapMatchingActivity extends AppCompatActivity {

  private static final String TAG = "MapMatchingActivity";

  private MapView mapView;
  private MapboxMap map;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // Mapbox access token is configured here. This needs to be called either in your application
    // object or in the same activity which contains the mapview.
    Mapbox.getInstance(this, getString(R.string.access_token));

    // This contains the MapView in XML and needs to be called after the access token is configured.
    setContentView(R.layout.activity_javaservices_map_matching);

    mapView = findViewById(R.id.mapView);
    mapView.onCreate(savedInstanceState);
    mapView.getMapAsync(new OnMapReadyCallback() {
      @Override
      public void onMapReady(@NonNull MapboxMap mapboxMap) {
        map = mapboxMap;
        map.setStyle(Style.MAPBOX_STREETS, new Style.OnStyleLoaded() {
          @Override
          public void onStyleLoaded(@NonNull Style style) {
            new LoadGeoJson(MapMatchingActivity.this).execute();
          }
        });
      }
    });
  }

  @Override
  protected void onStart() {
    super.onStart();
    mapView.onStart();
  }

  @Override
  public void onResume() {
    super.onResume();
    mapView.onResume();
  }

  @Override
  public void onPause() {
    super.onPause();
    mapView.onPause();
  }

  @Override
  public void onLowMemory() {
    super.onLowMemory();
    mapView.onLowMemory();
  }

  @Override
  protected void onStop() {
    super.onStop();
    mapView.onStop();
  }

  @Override
  protected void onDestroy() {
    super.onDestroy();
    mapView.onDestroy();
  }

  @Override
  protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    mapView.onSaveInstanceState(outState);
  }

  private static class LoadGeoJson extends AsyncTask<Void, Void, FeatureCollection> {

    private WeakReference<MapMatchingActivity> weakReference;

    LoadGeoJson(MapMatchingActivity activity) {
      this.weakReference = new WeakReference<>(activity);
    }

    @Override
    protected FeatureCollection doInBackground(Void... voids) {
      try {
        MapMatchingActivity activity = weakReference.get();
        if (activity != null) {
          InputStream inputStream = activity.getAssets().open("trace.geojson");
          return FeatureCollection.fromJson(convertStreamToString(inputStream));
        }
      } catch (Exception exception) {
        Timber.e("Exception Loading GeoJSON: %s", exception.toString());
      }
      return null;
    }

    static String convertStreamToString(InputStream is) {
      Scanner scanner = new Scanner(is).useDelimiter("\\A");
      return scanner.hasNext() ? scanner.next() : "";
    }

    @Override
    protected void onPostExecute(@Nullable FeatureCollection featureCollection) {
      super.onPostExecute(featureCollection);
      MapMatchingActivity activity = weakReference.get();
      if (activity != null && featureCollection != null) {
        activity.drawLines(featureCollection);
      }
    }
  }

  private void drawLines(@NonNull FeatureCollection featureCollection) {
    List<Feature> features = featureCollection.features();
    if (features != null && features.size() > 0) {
      Feature feature = features.get(0);
      drawBeforeMapMatching(feature);
      requestMapMatched(feature);
    }
  }

  private void drawBeforeMapMatching(Feature feature) {
    map.getStyle(style -> {
      style.addSource(new GeoJsonSource("pre-matched-source-id", feature));
      style.addLayer(new LineLayer("pre-matched-layer-id", "pre-matched-source-id").withProperties(
        lineColor(ColorUtils.colorToRgbaString(Color.parseColor("#c14a00"))),
        lineWidth(6f),
        lineOpacity(1f)
      ));
    });
  }

  private void requestMapMatched(Feature feature) {
    List<Point> points = ((LineString) Objects.requireNonNull(feature.geometry())).coordinates();

    try {
      // Setup the request using a client.
      MapboxMapMatching client = MapboxMapMatching.builder()
        .accessToken(Objects.requireNonNull(Mapbox.getAccessToken()))
        .profile(PROFILE_DRIVING)
        .coordinates(points)
        .build();

      // Execute the API call and handle the response.
      client.enqueueCall(new Callback<MapMatchingResponse>() {
        @Override
        public void onResponse(@NonNull Call<MapMatchingResponse> call,
                               @NonNull Response<MapMatchingResponse> response) {
          if (response.code() == 200) {
            drawMapMatched(Objects.requireNonNull(response.body()).matchings());
          } else {
            // If the response code does not response "OK" an error has occurred.
            Timber.e("MapboxMapMatching failed with %s", response.code());
          }
        }

        @Override
        public void onFailure(Call<MapMatchingResponse> call, Throwable throwable) {
          Timber.e(throwable, "MapboxMapMatching error");
        }
      });
    } catch (ServicesException servicesException) {
      Timber.e(servicesException, "MapboxMapMatching error");
    }
  }

  private void drawMapMatched(@NonNull List<MapMatchingMatching> matchings) {
    Style style = map.getStyle();
    if (style != null && !matchings.isEmpty()) {
      style.addSource(new GeoJsonSource("matched-source-id", Feature.fromGeometry(LineString.fromPolyline(
        Objects.requireNonNull(matchings.get(0).geometry()), PRECISION_6)))
      );
      style.addLayer(new LineLayer("matched-layer-id", "matched-source-id")
        .withProperties(
          lineColor(ColorUtils.colorToRgbaString(Color.parseColor("#3bb2d0"))),
          lineWidth(6f))
      );
    }
  }
}

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