You can use selection to identify a feature and learn more about it. ENC layers often have many overlapping features, and features of mixed geometry, in a single layer, so the sample includes code for identifying the smallest feature, which is taken to be the most relevant.
How to use the sample
Tap to select ENC features. Feature properties will be displayed in a callout.
How it works
Load and display the ENC layer.
When the map view is tapped, call mapView.IdentifyLayersAsync(), specifying the tapped position, a tolerance, and false for the popupsOnly parameter.
Filter the list of identified layers to include only results where the LayerContent is an EncLayer.
Get the first result with at least one feature.
Get the first feature in the IdentifyLayerResult.
Select that feature by calling identifyResult.LayerContent.SelectFeature(firstFeature).
Show the feature's acronym and description in a callout.
Relevant API
EncFeature
EncFeature.Acronym
EncFeature.Description
EncLayer
GeometryEngine.Area
IdentifyLayerResult
IdentifyLayerResult.GeoElements
IdentifyLayerResult.LayerContent
Offline data
This sample downloads the following items from ArcGIS Online automatically:
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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.using System;
using Android.App;
using Android.OS;
using Android.Widget;
using ArcGISRuntime.Samples.Managers;
using Esri.ArcGISRuntime.Data;
using Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Hydrography;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.UI;
using Esri.ArcGISRuntime.UI.Controls;
using System.Collections.Generic;
using System.Linq;
namespaceArcGISRuntime.Samples.SelectEncFeatures{
[Activity (ConfigurationChanges=Android.Content.PM.ConfigChanges.Orientation | Android.Content.PM.ConfigChanges.ScreenSize)]
[ArcGISRuntime.Samples.Shared.Attributes.OfflineData("9d2987a825c646468b3ce7512fb76e2d")]
[ArcGISRuntime.Samples.Shared.Attributes.Sample(
name: "Select ENC features",
category: "Hydrography",
description: "Select features in an ENC layer.",
instructions: "Tap to select ENC features. Feature properties will be displayed in a callout.",
tags: new[] { "IHO", "S-57", "S57", "chart", "hydrography", "identify", "maritime", "select", "selection" })]
publicclassSelectEncFeatures : Activity {
// Hold a reference to the map viewprivate MapView _myMapView;
protectedoverridevoidOnCreate(Bundle bundle) {
base.OnCreate(bundle);
Title = "Select ENC features";
// Create the UI, setup the control references and execute initialization CreateLayout();
Initialize();
}
privateasyncvoidInitialize() {
// Initialize the map with an oceans basemap _myMapView.Map = new Map(BasemapStyle.ArcGISOceans);
// Get the path to the ENC Exchange Setstring encPath = DataManager.GetDataFolder("9d2987a825c646468b3ce7512fb76e2d", "ExchangeSetwithoutUpdates", "ENC_ROOT", "CATALOG.031");
// Create the Exchange Set// Note: this constructor takes an array of paths because so that update sets can be loaded alongside base data EncExchangeSet myEncExchangeSet = new EncExchangeSet(encPath);
try {
// Wait for the exchange set to loadawait myEncExchangeSet.LoadAsync();
// Store a list of data set extent's - will be used to zoom the mapview to the full extent of the Exchange Set List<Envelope> dataSetExtents = new List<Envelope>();
// Add each data set as a layerforeach (EncDataset myEncDataset in myEncExchangeSet.Datasets)
{
// Create the cell and layer EncLayer myEncLayer = new EncLayer(new EncCell(myEncDataset));
// Add the layer to the map _myMapView.Map.OperationalLayers.Add(myEncLayer);
// Wait for the layer to loadawait myEncLayer.LoadAsync();
// Add the extent to the list of extents dataSetExtents.Add(myEncLayer.FullExtent);
}
// Use the geometry engine to compute the full extent of the ENC Exchange Set Envelope fullExtent = GeometryEngine.CombineExtents(dataSetExtents);
// Set the viewpoint _myMapView.SetViewpoint(new Viewpoint(fullExtent));
// Subscribe to tap events (in order to use them to identify and select features) _myMapView.GeoViewTapped += MyMapView_GeoViewTapped;
}
catch (Exception e)
{
new AlertDialog.Builder(this).SetMessage(e.ToString()).SetTitle("Error").Show();
}
}
privatevoidCreateLayout() {
// Create a new vertical layout for the app LinearLayout layout = new LinearLayout(this) { Orientation = Orientation.Vertical };
// Create a TextView for instructions. TextView sampleInstructionsTextView = new TextView(this)
{
Text = "Tap on the map to select an ENC feature." };
layout.AddView(sampleInstructionsTextView);
// Add the map view to the layout _myMapView = new MapView(this);
layout.AddView(_myMapView);
// Show the layout in the app SetContentView(layout);
}
privatevoidClearAllSelections() {
// For each layer in the operational layers that is an ENC layerforeach (EncLayer layer in _myMapView.Map.OperationalLayers.OfType<EncLayer>())
{
// Clear the layer's selection layer.ClearSelection();
}
// Clear the callout _myMapView.DismissCallout();
}
privateasyncvoidMyMapView_GeoViewTapped(object sender, GeoViewInputEventArgs e) {
// First clear any existing selections ClearAllSelections();
try {
// Perform the identify operation. IReadOnlyList<IdentifyLayerResult> results = await _myMapView.IdentifyLayersAsync(e.Position, 10, false);
// Return if there are no results.if (results.Count < 1) { return; }
// Get the results that are from ENC layers. IEnumerable<IdentifyLayerResult> encResults = results.Where(result => result.LayerContent is EncLayer);
// Get the first result with ENC features. (Depending on the data, there may be more than one IdentifyLayerResult that contains ENC features.) IdentifyLayerResult firstResult = encResults.First();
// Get the layer associated with this set of results. EncLayer containingLayer = (EncLayer)firstResult.LayerContent;
// Get the GeoElement identified in this layer. EncFeature encFeature = (EncFeature)firstResult.GeoElements.First();
// Select the feature. containingLayer.SelectFeature(encFeature);
// Create the callout definition. CalloutDefinition definition = new CalloutDefinition(encFeature.Acronym, encFeature.Description);
// Show the callout. _myMapView.ShowCalloutAt(e.Location, definition);
}
catch (Exception ex)
{
new AlertDialog.Builder(this).SetMessage(ex.ToString()).SetTitle("Error").Show();
}
}
privatestaticstringGetEncPath() {
return DataManager.GetDataFolder("a490098c60f64d3bbac10ad131cc62c7", "GB5X01NW.000");
}
}
}