Building outline
A newer version of the Maps SDK is available
This page uses v9.7.1 of the Mapbox Maps SDK. A newer version of the SDK is available. Learn about the latest version, v11.3.0, in the Maps SDK documentation.
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.
activity_query_building_outline
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:mapbox="http://schemas.android.com/apk/res-auto">
<com.mapbox.mapboxsdk.maps.MapView
android:id="@+id/mapView"
mapbox:mapbox_cameraTargetLat="39.951024"
mapbox:mapbox_cameraTargetLng="-75.164394"
mapbox:mapbox_cameraZoom="17.34"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</FrameLayout>
BuildingOutlineActivity.java
package com.mapbox.mapboxandroiddemo.examples.query;
import android.graphics.Color;
import android.graphics.PointF;
import android.os.Bundle;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import android.view.Gravity;
import android.view.View;
import android.widget.FrameLayout;
import android.widget.Toast;
import com.mapbox.geojson.Feature;
import com.mapbox.geojson.FeatureCollection;
import com.mapbox.geojson.LineString;
import com.mapbox.geojson.Point;
import com.mapbox.geojson.Polygon;
import com.mapbox.mapboxandroiddemo.R;
import com.mapbox.mapboxsdk.Mapbox;
import com.mapbox.mapboxsdk.geometry.LatLng;
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 java.util.ArrayList;
import java.util.List;
import static com.mapbox.mapboxsdk.style.layers.Property.LINE_CAP_ROUND;
import static com.mapbox.mapboxsdk.style.layers.Property.LINE_JOIN_BEVEL;
import static com.mapbox.mapboxsdk.style.layers.PropertyFactory.lineCap;
import static com.mapbox.mapboxsdk.style.layers.PropertyFactory.lineColor;
import static com.mapbox.mapboxsdk.style.layers.PropertyFactory.lineJoin;
import static com.mapbox.mapboxsdk.style.layers.PropertyFactory.lineWidth;
/**
* Query the building layer to draw an outline around the building that is in the middle of the map
*/
public class BuildingOutlineActivity extends AppCompatActivity implements
OnMapReadyCallback, MapboxMap.OnCameraIdleListener {
private MapView mapView;
private MapboxMap mapboxMap;
@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_query_building_outline);
mapView = findViewById(R.id.mapView);
mapView.onCreate(savedInstanceState);
mapView.getMapAsync(this);
}
@Override
public void onMapReady(@NonNull final MapboxMap mapboxMap) {
BuildingOutlineActivity.this.mapboxMap = mapboxMap;
mapboxMap.setStyle(Style.MAPBOX_STREETS, new Style.OnStyleLoaded() {
@Override
public void onStyleLoaded(@NonNull Style style) {
setUpLineLayer(style);
mapboxMap.addOnCameraIdleListener(BuildingOutlineActivity.this);
showCrosshair();
Toast.makeText(BuildingOutlineActivity.this, R.string.move_map_around_building_out_instruction,
Toast.LENGTH_SHORT).show();
updateOutline(style);
}
});
}
/**
* Sets up the source and layer for drawing the building outline
*/
private void setUpLineLayer(@NonNull Style loadedMapStyle) {
// Create a GeoJSONSource from an empty FeatureCollection
loadedMapStyle.addSource(new GeoJsonSource("source",
FeatureCollection.fromFeatures(new Feature[]{})));
// Use runtime styling to adjust the look of the building outline LineLayer
loadedMapStyle.addLayer(new LineLayer("lineLayer", "source").withProperties(
lineColor(Color.RED),
lineWidth(6f),
lineCap(LINE_CAP_ROUND),
lineJoin(LINE_JOIN_BEVEL)
));
}
@Override
public void onCameraIdle() {
mapboxMap.getStyle(new Style.OnStyleLoaded() {
@Override
public void onStyleLoaded(@NonNull Style style) {
updateOutline(style);
}
});
}
/**
* Query the map for a building Feature in the map's building layer. The query happens in the middle of the
* map ("the target"). If there's a building Feature in the middle of the map, its coordinates are turned
* into a list of Point objects so that a LineString can be created.
*
* @return the LineString built via the building's coordinates
*/
private LineString getBuildingFeatureOutline(@NonNull Style style) {
// Retrieve the middle of the map
final PointF pixel = mapboxMap.getProjection().toScreenLocation(new LatLng(
mapboxMap.getCameraPosition().target.getLatitude(),
mapboxMap.getCameraPosition().target.getLongitude()
));
List<Point> pointList = new ArrayList<>();
// Check whether the map style has a building layer
if (style.getLayer("building") != null) {
// Retrieve the building Feature that is displayed in the middle of the map
List<Feature> features = mapboxMap.queryRenderedFeatures(pixel, "building");
if (features.size() > 0) {
if (features.get(0).geometry() instanceof Polygon) {
Polygon buildingFeature = (Polygon) features.get(0).geometry();
// Build a list of Point objects from the building Feature's coordinates
if (buildingFeature != null) {
for (int i = 0; i < buildingFeature.coordinates().size(); i++) {
for (int j = 0;
j < buildingFeature.coordinates().get(i).size(); j++) {
pointList.add(Point.fromLngLat(
buildingFeature.coordinates().get(i).get(j).longitude(),
buildingFeature.coordinates().get(i).get(j).latitude()
));
}
}
}
}
// Create a LineString from the list of Point objects
}
} else {
Toast.makeText(this, R.string.building_layer_not_present, Toast.LENGTH_SHORT).show();
}
return LineString.fromLngLats(pointList);
}
/**
* Update the FeatureCollection used by the building outline LineLayer. Then refresh the map.
*/
private void updateOutline(@NonNull Style style) {
// Update the data source used by the building outline LineLayer and refresh the map
FeatureCollection featureCollection = FeatureCollection.fromFeatures(new Feature[]
{Feature.fromGeometry(getBuildingFeatureOutline(style))});
GeoJsonSource source = style.getSourceAs("source");
if (source != null) {
source.setGeoJson(featureCollection);
}
}
private void showCrosshair() {
View crosshair = new View(this);
crosshair.setLayoutParams(new FrameLayout.LayoutParams(20, 20, Gravity.CENTER));
crosshair.setBackgroundColor(Color.RED);
mapView.addView(crosshair);
}
@Override
public void onResume() {
super.onResume();
mapView.onResume();
}
@Override
protected void onStart() {
super.onStart();
mapView.onStart();
}
@Override
protected void onStop() {
super.onStop();
mapView.onStop();
}
@Override
public void onPause() {
super.onPause();
mapView.onPause();
}
@Override
public void onLowMemory() {
super.onLowMemory();
mapView.onLowMemory();
}
@Override
protected void onDestroy() {
super.onDestroy();
if (mapboxMap != null) {
mapboxMap.removeOnCameraIdleListener(this);
}
mapView.onDestroy();
}
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
mapView.onSaveInstanceState(outState);
}
}