Show labels on layer

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// Copyright 2025 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
//
//   https://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.
//

import 'package:arcgis_maps/arcgis_maps.dart';
import 'package:arcgis_maps_sdk_flutter_samples/common/common.dart';
import 'package:flutter/material.dart';

class ShowLabelsOnLayer extends StatefulWidget {
  const ShowLabelsOnLayer({super.key});

  @override
  State<ShowLabelsOnLayer> createState() => _ShowLabelsOnLayerState();
}

class _ShowLabelsOnLayerState extends State<ShowLabelsOnLayer>
    with SampleStateSupport {
  // Create a controller for the map view.
  final _mapViewController = ArcGISMapView.createController();
  // A flag for when the map view is ready and controls can be used.
  var _ready = false;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Stack(
        children: [
          // Add a map view to the widget tree and set a controller.
          ArcGISMapView(
            controllerProvider: () => _mapViewController,
            onMapViewReady: onMapViewReady,
          ),
          // Display a progress indicator and prevent interaction until state is ready.
          LoadingIndicator(visible: !_ready),
        ],
      ),
    );
  }

  Future<void> onMapViewReady() async {
    // Create a map with a light gray basemap style.
    final map = ArcGISMap.withBasemapStyle(BasemapStyle.arcGISLightGray);
    // Set the initial viewpoint near the center of the US.
    map.initialViewpoint = Viewpoint.fromCenter(
      ArcGISPoint(
        x: -10846309.950860,
        y: 4683272.219411,
        spatialReference: SpatialReference.webMercator,
      ),
      scale: 20000000,
    );

    // Set the map to the map view.
    _mapViewController.arcGISMap = map;

    // Create a feature layer from an online feature service of US Congressional Districts.
    const serviceUrl =
        'https://services.arcgis.com/P3ePLMYs2RVChkJx/arcgis/rest/services/USA_116th_Congressional_Districts/FeatureServer/0';
    final serviceFeatureTable = ServiceFeatureTable.withUri(
      Uri.parse(serviceUrl),
    );
    final featureLayer = FeatureLayer.withFeatureTable(serviceFeatureTable);

    // Add the feature layer to the map.
    map.operationalLayers.add(featureLayer);

    // Load the feature layer.
    await featureLayer.load();

    // Create label definitions for each party.
    final republicanLabelDefinition = makeLabelDefinition(
      'Republican',
      Colors.red,
    );
    final democratLabelDefinition = makeLabelDefinition(
      'Democrat',
      Colors.blue,
    );

    // Add the label definitions to the feature layer.
    featureLayer.labelDefinitions.addAll([
      republicanLabelDefinition,
      democratLabelDefinition,
    ]);

    // Enable labels on the feature layer.
    featureLayer.labelsEnabled = true;

    // Set the ready state variable to true to enable the sample UI.
    setState(() => _ready = true);
  }

  LabelDefinition makeLabelDefinition(String party, Color color) {
    // Create a text symbol for the label definition.
    final textSymbol = TextSymbol(color: color, size: 12);

    // Create a label definition with an Arcade expression script.
    final arcadeLabelExpression = ArcadeLabelExpression(
      arcadeString:
          r'$feature.NAME + " (" + left($feature.PARTY,1) + ")\nDistrict " + $feature.CDFIPS',
    );

    // Create the label definition.
    final labelDefinition = LabelDefinition(
      labelExpression: arcadeLabelExpression,
      textSymbol: textSymbol,
    );

    // Set the placement for the label definition.
    labelDefinition.placement = LabelingPlacement.polygonAlwaysHorizontal;
    // Create a where clause for the label definition.
    labelDefinition.whereClause = "PARTY = '$party'";

    // Return the label definition.
    return labelDefinition;
  }
}