Identify raster cell

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
// 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';
import 'package:path_provider/path_provider.dart';

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

  @override
  State<IdentifyRasterCell> createState() => _IdentifyRasterCellState();
}

class _IdentifyRasterCellState extends State<IdentifyRasterCell>
    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;
  // Raster layer to display raster data on the map.
  late RasterLayer _rasterLayer;
  // Graphic to get the raster cell information.
  final Graphic _textGraphic = Graphic();
  // Graphics overlay to display the text graphic.
  final _textGraphicsOverlay = GraphicsOverlay();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Stack(
        children: [
          ArcGISMapView(
            controllerProvider: () => _mapViewController,
            onMapViewReady: onMapViewReady,
            onTap: onTap,
          ),
          LoadingIndicator(visible: !_ready),
        ],
      ),
    );
  }

  Future<void> onMapViewReady() async {
    // Create a map with the oceans basemap style.
    final map = ArcGISMap.withBasemapStyle(BasemapStyle.arcGISOceans);
    // Add map to the map view.
    _mapViewController.arcGISMap = map;
    // Load the raster layer.
    await loadRasterLayer();
    // Add the Raster Layer to the map.
    map.operationalLayers.add(_rasterLayer);
    // Set the viewpoint.
    if (_rasterLayer.fullExtent != null) {
      await _mapViewController.setViewpointGeometry(_rasterLayer.fullExtent!);
    }
    // Add the text graphic to the text graphics overlay.
    _textGraphicsOverlay.graphics.add(_textGraphic);
    // Add the text graphics overlay to the map view.
    _mapViewController.graphicsOverlays.add(_textGraphicsOverlay);
    // Set the ready state variable to true to enable the sample UI.
    setState(() => _ready = true);
  }

  Future<void> onTap(Offset position) async {
    // Get the result for where the user tapped on the raster layer.
    final identifyResult = await _mapViewController.identifyLayer(
      _rasterLayer,
      screenPoint: position,
      tolerance: 1,
    );
    // Get the identified raster cell.
    if (identifyResult.geoElements.isNotEmpty) {
      // Create a StringBuffer to display information to the user.
      final stringBuffer = StringBuffer();
      final cell = identifyResult.geoElements.first;
      // Loop through the attributes (key/value pairs).
      cell.attributes.forEach((key, value) {
        stringBuffer.writeln('$key: $value');
      });
      // Get the x and y values of the cell.
      if (cell.geometry != null) {
        final x = cell.geometry!.extent.xMin;
        final y = cell.geometry!.extent.yMin;
        // Add the x & y coordinates where the user clicked raster cell to the string buffer.
        stringBuffer.writeln();
        stringBuffer.writeln('X: ${x.toStringAsFixed(4)}');
        stringBuffer.write('Y: ${y.toStringAsFixed(4)}');

        final textSymbol = TextSymbol(
          color: Colors.white,
          size: 12,
          text: stringBuffer.toString(),
          horizontalAlignment: HorizontalAlignment.left,
        );
        textSymbol.backgroundColor = Colors.black.withValues(alpha: 0.8);
        _textGraphic.geometry = cell.geometry;
        _textGraphicsOverlay.renderer = SimpleRenderer(symbol: textSymbol);
      }
    } else {
      _textGraphicsOverlay.renderer = null;
    }
  }

  Future<void> loadRasterLayer() async {
    // Download the raster file.
    await downloadSampleData(['b5f977c78ec74b3a8857ca86d1d9b318']);
    // Get the application documents directory.
    final appDir = await getApplicationDocumentsDirectory();
    // Create a Raster from the local tif file.
    final raster = Raster.withFileUri(
      Uri.file(
        '${appDir.absolute.path}/SA_EVI_8Day_03May20/SA_EVI_8Day_03May20.tif',
      ),
    );
    // Create a Raster Layer.
    _rasterLayer = RasterLayer.withRaster(raster);
    // Load the Raster Layer.
    await _rasterLayer.load();
  }
}