Identify KML features

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Sample viewer app

Show a callout with formatted content for a KML feature.

Image of identify KML features

Use case

A user may wish to select a KML feature to view relevant information about it.

How to use the sample

Tap a feature to identify it. Feature information will be displayed in a callout.

Note: the KML layer used in this sample contains a screen overlay. The screen overlay contains a legend and the logos for NOAA and the NWS. You can't identify the screen overlay.

How it works

  1. Create an OnTouchListener on the MapView.
  2. On tap:
  3. Dismiss the Callout, if one is showing.
  4. Call MapView.identifyLayerAsync(...) passing in the KmlLayer, screen point and tolerance.
  5. Await the result of the identify and then get the KmlPlacemark from the result.
  6. Create a callout at the calculated map point and populate the callout content with text from the placemark's BalloonContent. NOTE: KML supports defining HTML for balloon content and may need to be converted from HTML to text.
  7. Show the callout.

Note: There are several types of KML features. This sample only identifies features of type KmlPlacemark.

Relevant API

  • GeoView.identifyLayerAsync
  • IdentifyLayerResult
  • KmlLayer
  • KmlPlacemark

About the data

This sample shows a forecast for significant weather within the U.S. Regions of severe thunderstorms, flooding, snowfall, and freezing rain are shown. Tap the features to see details.

Additional information

KML features can have rich HTML content, including images.

Tags

Keyhole, KML, KMZ, NOAA, NWS, OGC, weather

Sample Code

MainActivity.java
                                                                                                                                      
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/*
 *  Copyright 2019 Esri
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package com.esri.arcgisruntime.sample.identifykmlfeatures;

import java.util.concurrent.ExecutionException;

import android.os.Bundle;
import android.text.Html;
import android.util.Log;
import android.view.MotionEvent;
import android.widget.TextView;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;
import com.esri.arcgisruntime.ArcGISRuntimeEnvironment;
import com.esri.arcgisruntime.concurrent.ListenableFuture;
import com.esri.arcgisruntime.geometry.Envelope;
import com.esri.arcgisruntime.geometry.SpatialReferences;
import com.esri.arcgisruntime.layers.KmlLayer;
import com.esri.arcgisruntime.mapping.ArcGISMap;
import com.esri.arcgisruntime.mapping.BasemapStyle;
import com.esri.arcgisruntime.mapping.GeoElement;
import com.esri.arcgisruntime.mapping.view.Callout;
import com.esri.arcgisruntime.mapping.view.DefaultMapViewOnTouchListener;
import com.esri.arcgisruntime.mapping.view.IdentifyLayerResult;
import com.esri.arcgisruntime.mapping.view.MapView;
import com.esri.arcgisruntime.ogc.kml.KmlDataset;
import com.esri.arcgisruntime.ogc.kml.KmlPlacemark;

public class MainActivity extends AppCompatActivity {

  private static final String TAG = MainActivity.class.getSimpleName();

  private MapView mMapView;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    // authentication with an API key or named user is required to access basemaps and other
    // location services
    ArcGISRuntimeEnvironment.setApiKey(BuildConfig.API_KEY);

    // create a map and add it to the map view
    ArcGISMap map = new ArcGISMap(BasemapStyle.ARCGIS_DARK_GRAY);
    mMapView = findViewById(R.id.mapView);
    mMapView.setMap(map);

    // start zoomed in over the US
    mMapView.setViewpointGeometryAsync(
        new Envelope(-19195297.778679, 512343.939994, -3620418.579987, 8658913.035426, 0.0, 0.0,
            SpatialReferences.getWebMercator()));

    // create a KML dataset of weather forecasts
    KmlDataset forecastKmlDataset = new KmlDataset("https://www.wpc.ncep.noaa.gov/kml/noaa_chart/WPC_Day1_SigWx.kml");

    // create a KML layer and add it as an operational layer
    KmlLayer forecastKmlLayer = new KmlLayer(forecastKmlDataset);
    map.getOperationalLayers().add(forecastKmlLayer);

    // add a click listener to identify clicked features
    mMapView.setOnTouchListener(new DefaultMapViewOnTouchListener(this, mMapView) {

      @Override public boolean onSingleTapConfirmed(MotionEvent e) {
        // hide the callout if it's showing
        mMapView.getCallout().dismiss();

        // get the identified geoelements at the clicked location
        android.graphics.Point screenPoint = new android.graphics.Point(Math.round(e.getX()), Math.round(e.getY()));
        ListenableFuture<IdentifyLayerResult> identify = mMapView
            .identifyLayerAsync(forecastKmlLayer, screenPoint, 5, false);
        identify.addDoneListener(() -> {
          try {
            IdentifyLayerResult result = identify.get();
            // find the first geoElement that is a KML placemark
            for (GeoElement geoElement : result.getElements()) {
              if (geoElement instanceof KmlPlacemark) {
                // show a callout at the placemark with custom content using the placemark's "balloon content"
                KmlPlacemark placemark = (KmlPlacemark) geoElement;
                TextView calloutContent = new TextView(getApplicationContext());
                calloutContent.setText(Html.fromHtml(placemark.getBalloonContent()));

                // get callout, set content and show
                Callout callout = mMapView.getCallout();
                callout.setLocation(mMapView.screenToLocation(screenPoint));
                callout.setContent(calloutContent);
                callout.show();
                break;
              }
            }
          } catch (InterruptedException | ExecutionException ex) {
            String error = "Error identifying features in layer: " + ex.getMessage();
            Toast.makeText(MainActivity.this, error, Toast.LENGTH_LONG).show();
            Log.e(TAG, error);
          }
        });
        return true;
      }
    });
  }

  @Override
  protected void onPause() {
    mMapView.pause();
    super.onPause();
  }

  @Override
  protected void onResume() {
    super.onResume();
    mMapView.resume();
  }

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

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