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PaulAllanSturmPaulAllanSturm
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Merge pull request #73 from Esri/PaulAllanSturm/identifyLayerFeatures
Update "Identify layer features"
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‎assets/generated_samples_list.json‎

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"category": "Search and Query",
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"description": "Identify features in all layers in a map.",
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"ignore": false,
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"images": [],
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"keywords": [],
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"images": [
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"identify_layer_features.png"
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],
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"keywords": [
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"identify",
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"recursion",
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"recursive",
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"sublayers",
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"ArcGISMapViewController.identifyLayers",
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"IdentifyLayerResult",
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"IdentifyLayerResult.layerContent.name",
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"IdentifyLayerResult.sublayerResults"
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],
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"redirect_from": [],
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"relevant_apis": [],
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"snippets": [],
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"relevant_apis": [
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"ArcGISMapViewController.identifyLayers",
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"IdentifyLayerResult",
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"IdentifyLayerResult.layerContent.name",
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"IdentifyLayerResult.sublayerResults"
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],
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"snippets": [
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"identify_layer_features_sample.dart"
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],
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"title": "Identify layer features",
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"key": "identify_layer_features"
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},

‎lib/samples/identify_layer_features/README.md‎

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# Identify layer features
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Identify features in all layers in a map.
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![Image of identify layer features](identify_layer_features.png)
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## Use case
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`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.
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## How to use the sample
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Tap to identify features. A banner will list layers with features under the tapped location, as well as a layer count.
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## How it works
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1. The tapped position is passed to `ArcGISMapViewController.identifyLayers`.
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2. For each `IdentifyLayerResult` in the results, features are counted.
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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.
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## Relevant API
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* ArcGISMapViewController.identifyLayers
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* IdentifyLayerResult
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* IdentifyLayerResult.layerContent.name
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* IdentifyLayerResult.sublayerResults
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## Additional information
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The `GeoViewController` supports two methods of identify: `identifyLayer()`, which identifies features within a specific layer, and `identifyLayers()`, which identifies features for all layers in the current view.
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## Tags
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identify, recursion, recursive, sublayers

‎lib/samples/identify_layer_features/README.metadata.json‎

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"category": "Search and Query",
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"description": "Identify features in all layers in a map.",
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"ignore": false,
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"images": [],
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"keywords": [],
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"images": [
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"identify_layer_features.png"
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],
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"keywords": [
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"identify",
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"recursion",
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"recursive",
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"sublayers",
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"ArcGISMapViewController.identifyLayers",
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"IdentifyLayerResult",
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"IdentifyLayerResult.layerContent.name",
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"IdentifyLayerResult.sublayerResults"
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],
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"redirect_from": [],
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"relevant_apis": [],
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"snippets": [],
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"relevant_apis": [
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"ArcGISMapViewController.identifyLayers",
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"IdentifyLayerResult",
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"IdentifyLayerResult.layerContent.name",
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"IdentifyLayerResult.sublayerResults"
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],
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"snippets": [
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"identify_layer_features_sample.dart"
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],
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"title": "Identify layer features"
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}

‎lib/samples/identify_layer_features/identify_layer_features.png‎

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‎lib/samples/identify_layer_features/identify_layer_features_sample.dart‎

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@@ -29,14 +29,67 @@ class IdentifyLayerFeaturesSample extends StatefulWidget {
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class _IdentifyLayerFeaturesSampleState
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extends State<IdentifyLayerFeaturesSample> with SampleStateSupport {
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// Create a controller for the map view.
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final _mapViewController = ArcGISMapView.createController();
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// A flag for when the map view is ready and controls can be used.
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var _ready = false;
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// The message to display in the result banner.
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var _message = '';
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@override
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void initState() {
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super.initState();
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Widget build(BuildContext context) {
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return Scaffold(
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body: Stack(
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children: [
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// Add a map view to the widget tree and set a controller.
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ArcGISMapView(
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controllerProvider: () => _mapViewController,
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onMapViewReady: onMapViewReady,
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onTap: onTap,
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),
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// Add a banner to show the results of the identify operation.
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SafeArea(
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child: IgnorePointer(
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child: Container(
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color: Colors.white.withAlpha(230),
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padding: const EdgeInsets.all(10),
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child: Row(
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children: [Text(_message)],
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),
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),
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),
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),
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// Display a progress indicator and prevent interaction until state is ready.
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Visibility(
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visible: !_ready,
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child: SizedBox.expand(
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child: Container(
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color: Colors.white30,
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child: const Center(child: CircularProgressIndicator()),
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),
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),
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),
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],
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),
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);
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}
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final map = ArcGISMap.withBasemapStyle(BasemapStyle.arcGISTopographic);
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void onMapViewReady() async {
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// Create a feature layer of damaged property data.
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final serviceFeatureTable = ServiceFeatureTable.withUri(Uri.parse(
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'https://sampleserver6.arcgisonline.com/arcgis/rest/services/DamageAssessment/FeatureServer/0'));
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final featureLayer = FeatureLayer.withFeatureTable(serviceFeatureTable);
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// Create a layer with world cities data.
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final mapImageLayer = ArcGISMapImageLayer.withUri(Uri.parse(
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'https://sampleserver6.arcgisonline.com/arcgis/rest/services/SampleWorldCities/MapServer'));
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await mapImageLayer.load();
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// Hide continent and world layers.
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mapImageLayer.subLayerContents[1].isVisible = false;
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mapImageLayer.subLayerContents[2].isVisible = false;
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// Create a map with a basemap style and an initial viewpoint.
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final map = ArcGISMap.withBasemapStyle(BasemapStyle.arcGISTopographic);
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map.initialViewpoint = Viewpoint.fromCenter(
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ArcGISPoint(
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x: -10977012.785807,
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scale: 68015210,
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);
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final serviceFeatureTable = ServiceFeatureTable.withUri(Uri.parse(
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'https://sampleserver6.arcgisonline.com/arcgis/rest/services/DamageAssessment/FeatureServer/0'));
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final featureLayer = FeatureLayer.withFeatureTable(serviceFeatureTable);
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map.operationalLayers.add(featureLayer);
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// Add the layers to the map.
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map.operationalLayers.addAll([featureLayer, mapImageLayer]);
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// Add the map to the map view.
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_mapViewController.arcGISMap = map;
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_mapViewController.magnifierEnabled = true;
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}
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@override
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Widget build(BuildContext context) {
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return Scaffold(
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body: ArcGISMapView(
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controllerProvider: () => _mapViewController,
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onTap: onTap,
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onLongPressEnd: onTap,
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),
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);
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// Set the ready state variable to true to enable the sample UI.
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setState(() {
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_message = 'Tap on the map to identify layer features.';
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_ready = true;
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});
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}
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void onTap(Offset localPosition) async {
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// Identify features at the tapped location.
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final identifyLayerResults = await _mapViewController.identifyLayers(
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screenPoint: localPosition,
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tolerance: 12.0,
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maximumResultsPerLayer: 10,
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);
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if (identifyLayerResults.isNotEmpty && mounted) {
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int count = identifyLayerResults.length;
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showDialog(
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context: context,
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builder: (BuildContext context) {
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return AlertDialog(content: Text('Found $count'));
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},
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);
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// Count the number of identified features.
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var identifyTotal = 0;
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final layerCounts = <String>[];
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for (final result in identifyLayerResults) {
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final layerTotal = result.totalCount;
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identifyTotal += layerTotal;
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layerCounts.add('${result.layerContent.name}: $layerTotal');
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}
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// Display the results in the banner.
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setState(() {
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_message = identifyTotal == 0
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? 'No features identified.'
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: layerCounts.join('\n');
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});
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}
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}
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extension on IdentifyLayerResult {
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// The total count of features, recursively including all sublayers.
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int get totalCount {
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return sublayerResults.fold(geoElements.length,
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(previous, element) => previous + element.totalCount);
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}
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}

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