Simplify a polyline
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.
<?xml version="1.0" encoding="utf-8"?><LinearLayoutxmlns: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.SimplifyPolylineActivity"> <com.mapbox.mapboxsdk.maps.MapViewandroid:id="@+id/mapView"android:layout_width="match_parent"android:layout_height="match_parent"mapbox:mapbox_cameraTargetLat="37.692465"mapbox:mapbox_cameraTargetLng="-122.410413"mapbox:mapbox_cameraTilt="45"mapbox:mapbox_cameraZoom="10.5"/> </LinearLayout>
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.geojson.Feature;import com.mapbox.geojson.FeatureCollection;import com.mapbox.geojson.LineString;import com.mapbox.geojson.Point;import com.mapbox.geojson.utils.PolylineUtils;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 timber.log.Timber; import static com.mapbox.mapboxsdk.style.layers.PropertyFactory.lineColor;import static com.mapbox.mapboxsdk.style.layers.PropertyFactory.lineWidth; /*** Using the polylines utility, simplify a polyline at a* given tolerance to reduce the number of coordinates in that polyline.*/public class SimplifyPolylineActivity extends AppCompatActivity { private static final String TAG = "SimplifyLineActivity"; private MapView mapView;private MapboxMap map; @Overrideprotected 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_simplify_polyline); mapView = findViewById(R.id.mapView);mapView.onCreate(savedInstanceState);mapView.getMapAsync(new OnMapReadyCallback() {@Overridepublic void onMapReady(@NonNull MapboxMap mapboxMap) {map = mapboxMap;mapboxMap.setStyle(Style.LIGHT, new Style.OnStyleLoaded() {@Overridepublic void onStyleLoaded(@NonNull Style style) {new DrawGeoJson(SimplifyPolylineActivity.this).execute();}});}});} @Overridepublic void onResume() {super.onResume();mapView.onResume();} @Overrideprotected void onStart() {super.onStart();mapView.onStart();} @Overrideprotected void onStop() {super.onStop();mapView.onStop();} @Overridepublic void onPause() {super.onPause();mapView.onPause();} @Overridepublic void onLowMemory() {super.onLowMemory();mapView.onLowMemory();} @Overrideprotected void onDestroy() {super.onDestroy();mapView.onDestroy();} @Overrideprotected void onSaveInstanceState(Bundle outState) {super.onSaveInstanceState(outState);mapView.onSaveInstanceState(outState);} private static class DrawGeoJson extends AsyncTask<Void, Void, FeatureCollection> { private WeakReference<SimplifyPolylineActivity> weakReference; DrawGeoJson(SimplifyPolylineActivity activity) {this.weakReference = new WeakReference<>(activity);} @Overrideprotected FeatureCollection doInBackground(Void... voids) {try {SimplifyPolylineActivity activity = weakReference.get();if (activity != null) {InputStream inputStream = activity.getAssets().open("matched_route.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() : "";} @Overrideprotected void onPostExecute(@Nullable FeatureCollection featureCollection) {super.onPostExecute(featureCollection);SimplifyPolylineActivity 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);drawBeforeSimplify(feature);drawSimplify(feature);}} private void drawBeforeSimplify(@NonNull Feature lineStringFeature) {addLine("rawLine", lineStringFeature, "#8a8acb");} private void drawSimplify(@NonNull Feature feature) {List<Point> points = ((LineString) Objects.requireNonNull(feature.geometry())).coordinates();List<Point> after = PolylineUtils.simplify(points, 0.001);addLine("simplifiedLine", Feature.fromGeometry(LineString.fromLngLats(after)), "#3bb2d0");} private void addLine(String layerId, Feature feature, String lineColorHex) {map.getStyle(style -> {style.addSource(new GeoJsonSource(layerId, feature));style.addLayer(new LineLayer(layerId, layerId).withProperties(lineColor(ColorUtils.colorToRgbaString(Color.parseColor(lineColorHex))),lineWidth(4f)));});}}
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