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. The dependencies can be found here.The examples use View binding.See setup documention if necessary.
activity_simplify_polyline
<?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.SimplifyPolylineActivity">
<com.mapbox.mapboxsdk.maps.MapView
android: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>
SimplifyPolylineActivity.java
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;
@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_simplify_polyline);
mapView = findViewById(R.id.mapView);
mapView.onCreate(savedInstanceState);
mapView.getMapAsync(new OnMapReadyCallback() {
@Override
public void onMapReady(@NonNull MapboxMap mapboxMap) {
map = mapboxMap;
mapboxMap.setStyle(Style.LIGHT, new Style.OnStyleLoaded() {
@Override
public void onStyleLoaded(@NonNull Style style) {
new DrawGeoJson(SimplifyPolylineActivity.this).execute();
}
});
}
});
}
@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();
mapView.onDestroy();
}
@Override
protected 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);
}
@Override
protected 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() : "";
}
@Override
protected 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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