IdentifyLayers allows users to tap on a map, returning features at that location across multiple layers. Because some layer types have sublayers, the sample recursively counts results for sublayers within each layer.
How to use the sample
Tap to identify features. An alert will show all layers with features under the tapped location, as well as the number of features.
How it works
The tapped position is passed to MapView.identifyLayersAsync(...)
For each IdentifyLayerResult in the results, features are counted.
Note: there is one identify result per layer with matching features; if the feature count is 0, that means a sublayer contains the matching features.
Relevant API
IdentifyLayerResult
IdentifyLayerResult.sublayerResults
MapView.identifyLayersAsync(...)
Additional information
The GeoView supports two methods of identify: identifyLayerAsync(...), which identifies features within a specific layer and identifyLayersAsync(...), which identifies features for all layers in the current view.
Tags
identify, recursion, recursive, sublayers
Sample Code
MainActivity.kt
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/*
* Copyright 2020 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.identifylayers
import android.os.Bundle
import android.util.Log
import android.view.MotionEvent
import android.widget.Toast
import androidx.appcompat.app.AlertDialog.Builder
import androidx.appcompat.app.AppCompatActivity
import com.esri.arcgisruntime.ArcGISRuntimeEnvironment
import com.esri.arcgisruntime.data.ServiceFeatureTable
import com.esri.arcgisruntime.geometry.Point
import com.esri.arcgisruntime.geometry.SpatialReference
import com.esri.arcgisruntime.layers.ArcGISMapImageLayer
import com.esri.arcgisruntime.layers.FeatureLayer
import com.esri.arcgisruntime.mapping.ArcGISMap
import com.esri.arcgisruntime.mapping.BasemapStyle
import com.esri.arcgisruntime.mapping.Viewpoint
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.sample.identifylayers.databinding.ActivityMainBinding
import kotlin.math.roundToInt
classMainActivity : AppCompatActivity() {
privateval activityMainBinding by lazy {
ActivityMainBinding.inflate(layoutInflater)
}
privateval mapView: MapView by lazy {
activityMainBinding.mapView
}
overridefunonCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(activityMainBinding.root)
// authentication with an API key or named user is required to access basemaps and other// location services ArcGISRuntimeEnvironment.setApiKey(BuildConfig.API_KEY)
// create a feature layer of damaged property dataval featureTable = ServiceFeatureTable(getString(R.string.damage_assessment))
val featureLayer = FeatureLayer(featureTable)
// create a layer with world cities dataval mapImageLayer = ArcGISMapImageLayer(getString(R.string.world_cities)).apply {
addDoneLoadingListener {
// hide continent and world layers subLayerContents[1].isVisible = false subLayerContents[2].isVisible = false }
}
// create a topographic mapval map = ArcGISMap(BasemapStyle.ARCGIS_TOPOGRAPHIC).apply {
// add world cities layer operationalLayers.add(mapImageLayer)
// add damaged property data operationalLayers.add(featureLayer)
}
mapView.apply {
// assign the map to the map viewthis.map = map
// set the map's initial viewpoint setViewpoint(
Viewpoint(
Point(-10977012.785807, 4514257.550369, SpatialReference.create(3857)),
68015210.0 )
)
// add a listener to detect taps on the map view onTouchListener = object : DefaultMapViewOnTouchListener(this@MainActivity, this) {
overridefunonSingleTapConfirmed(e: MotionEvent?): Boolean {
e?.let {
val screenPoint = android.graphics.Point(
it.x.roundToInt(),
it.y.roundToInt()
)
identifyResult(screenPoint)
}
returntrue }
}
}
}
/**
* Performs an identify on layers at the given screenpoint and calls handleIdentifyResults(...) to process them.
*
* @param screenPoint in Android graphic coordinates.
*/privatefunidentifyResult(screenPoint: android.graphics.Point) {
val identifyLayerResultsFuture = mapView
.identifyLayersAsync(screenPoint, 12.0, false, 10)
identifyLayerResultsFuture.addDoneListener {
try {
val identifyLayerResults = identifyLayerResultsFuture.get()
handleIdentifyResults(identifyLayerResults)
} catch (e: Exception) {
logError("Error identifying results ${e.message}")
}
}
}
/**
* Processes identify results into a string which is passed to showAlertDialog(...).
*
* @param identifyLayerResults a list of identify results generated in identifyResult().
*/privatefunhandleIdentifyResults(identifyLayerResults: List<IdentifyLayerResult>) {
val message = StringBuilder()
var totalCount = 0for (identifyLayerResult in identifyLayerResults) {
val count = recursivelyCountIdentifyResultsForSublayers(identifyLayerResult)
val layerName = identifyLayerResult.layerContent.name
message.append(layerName).append(": ").append(count)
// add new line character if not the final element in arrayif (identifyLayerResult != identifyLayerResults[identifyLayerResults.size - 1]) {
message.append("\n")
}
totalCount += count
}
// if any elements were found show the results, else notify user that no elements were foundif (totalCount > 0) {
showAlertDialog(message)
} else {
logError("No element found")
}
}
/**
* Gets a count of the GeoElements in the passed result layer.
* This method recursively calls itself to descend into sublayers and count their results.
* @param result from a single layer.
* @return the total count of GeoElements.
*/privatefunrecursivelyCountIdentifyResultsForSublayers(result: IdentifyLayerResult): Int {
var subLayerGeoElementCount = 0for (sublayerResult in result.sublayerResults) {
// recursively call this function to accumulate elements from all sublayers subLayerGeoElementCount += recursivelyCountIdentifyResultsForSublayers(sublayerResult)
}
return subLayerGeoElementCount + result.elements.size
}
/**
* Shows message in an AlertDialog.
*
* @param message contains identify results processed into a string.
*/privatefunshowAlertDialog(message: StringBuilder) {
val alertDialogBuilder = Builder(this)
// set title alertDialogBuilder.setTitle("Number of elements found")
// set dialog message alertDialogBuilder
.setMessage(message)
.setCancelable(false)
.setPositiveButton(getString(R.string.ok)) { dialog, which -> }
// create alert dialogval alertDialog = alertDialogBuilder.create()
// show the alert dialog alertDialog.show()
}
overridefunonResume() {
super.onResume()
mapView.resume()
}
overridefunonPause() {
mapView.pause()
super.onPause()
}
overridefunonDestroy() {
mapView.dispose()
super.onDestroy()
}
/**
* Log an error to logcat and to the screen via Toast.
* @param message the text to log.
*/privatefunlogError(message: String?) {
message?.let {
Log.e(
TAG,
message
)
Toast.makeText(this, message, Toast.LENGTH_LONG).show()
}
}
privatecompanionobject {
privateval TAG: String = MainActivity::class.java.simpleName
}
}