Generate offline map

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//
// Copyright 2024 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 'dart:io';

import 'package:arcgis_maps/arcgis_maps.dart';
import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';

import '../../utils/sample_state_support.dart';

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

  @override
  State<GenerateOfflineMap> createState() => _GenerateOfflineMapState();
}

class _GenerateOfflineMapState extends State<GenerateOfflineMap>
    with SampleStateSupport {
  // Create a controller for the map view.
  final _mapViewController = ArcGISMapView.createController();
  // Declare a map to be loaded later.
  late final ArcGISMap _map;
  // Declare the OfflineMapTask.
  late final OfflineMapTask _offlineMapTask;
  // Declare the GenerateOfflineMapJob.
  GenerateOfflineMapJob? _generateOfflineMapJob;
  // Progress of the GenerateOfflineMapJob.
  int? _progress;
  // A flag for when the map is viewing offline data.
  var _offline = false;
  // A flag for when the map view is ready and controls can be used.
  var _ready = false;
  // Declare global keys to be used when converting screen locations to map coordinates.
  final _mapKey = GlobalKey();
  final _outlineKey = GlobalKey();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(
        top: false,
        child: Stack(
          children: [
            Column(
              children: [
                Expanded(
                  child: Stack(
                    children: [
                      // Add a map view to the widget tree and set a controller.
                      ArcGISMapView(
                        key: _mapKey,
                        controllerProvider: () => _mapViewController,
                        onMapViewReady: onMapViewReady,
                      ),
                      // Add a red outline that marks the region to be taken offline.
                      Visibility(
                        visible: _progress == null && !_offline,
                        child: IgnorePointer(
                          child: SafeArea(
                            child: Container(
                              margin: const EdgeInsets.fromLTRB(
                                30.0,
                                30.0,
                                30.0,
                                50.0,
                              ),
                              child: Container(
                                key: _outlineKey,
                                decoration: BoxDecoration(
                                  border: Border.all(
                                    color: Colors.red,
                                    width: 2.0,
                                  ),
                                ),
                              ),
                            ),
                          ),
                        ),
                      ),
                    ],
                  ),
                ),
                Center(
                  // Add a button to take the outlined region offline.
                  child: ElevatedButton(
                    onPressed:
                        _progress != null || _offline ? null : takeOffline,
                    child: const Text('Take Map Offline'),
                  ),
                ),
              ],
            ),
            // Display a progress indicator and prevent interaction until state is ready.
            Visibility(
              visible: !_ready,
              child: SizedBox.expand(
                child: Container(
                  color: Colors.white30,
                  child: const Center(child: CircularProgressIndicator()),
                ),
              ),
            ),
            // Display a progress indicator and a cancel button during the offline map generation.
            Visibility(
              visible: _progress != null,
              child: Center(
                child: Container(
                  width: MediaQuery.of(context).size.width / 2,
                  padding: const EdgeInsets.all(20.0),
                  decoration: BoxDecoration(
                    color: Colors.white,
                    borderRadius: BorderRadius.circular(10.0),
                  ),
                  child: Column(
                    mainAxisSize: MainAxisSize.min,
                    children: [
                      // Add a progress indicator.
                      Text('$_progress%'),
                      LinearProgressIndicator(
                        value: _progress != null ? _progress! / 100.0 : 0.0,
                      ),
                      const SizedBox(height: 20.0),
                      // Add a button to cancel the job.
                      ElevatedButton(
                        onPressed: () => _generateOfflineMapJob?.cancel(),
                        child: const Text('Cancel'),
                      ),
                    ],
                  ),
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }

  void onMapViewReady() async {
    // Create the map from a portal item.
    final portalItem = PortalItem.withPortalAndItemId(
      portal: Portal.arcGISOnline(),
      itemId: 'acc027394bc84c2fb04d1ed317aac674',
    );
    _map = ArcGISMap.withItem(portalItem);
    _mapViewController.arcGISMap = _map;

    // Offline map generation does not consider rotation, so disable it.
    _mapViewController.interactionOptions.rotateEnabled = false;

    // Create an OfflineMapTask for the map.
    _offlineMapTask = OfflineMapTask.withOnlineMap(_map);

    setState(() => _ready = true);
  }

  // Calculate the Envelope of the outlined region.
  Envelope? outlineEnvelope() {
    final outlineContext = _outlineKey.currentContext;
    final mapContext = _mapKey.currentContext;
    if (outlineContext == null || mapContext == null) return null;

    // Get the global screen rect of the outlined region.
    final outlineRenderBox = outlineContext.findRenderObject() as RenderBox;
    final outlineGlobalScreenRect =
        outlineRenderBox.localToGlobal(Offset.zero) & outlineRenderBox.size;

    // Convert the global screen rect to a rect local to the map view.
    final mapRenderBox = mapContext.findRenderObject() as RenderBox;
    final mapLocalScreenRect =
        outlineGlobalScreenRect.shift(-mapRenderBox.localToGlobal(Offset.zero));

    // Convert the local screen rect to map coordinates.
    final locationTopLeft =
        _mapViewController.screenToLocation(screen: mapLocalScreenRect.topLeft);
    final locationBottomRight = _mapViewController.screenToLocation(
      screen: mapLocalScreenRect.bottomRight,
    );
    if (locationTopLeft == null || locationBottomRight == null) return null;

    // Create an Envelope from the map coordinates.
    return Envelope.fromPoints(locationTopLeft, locationBottomRight);
  }

  // Take the selected region offline.
  void takeOffline() async {
    // Get the Envelope of the outlined region.
    final envelope = outlineEnvelope();
    if (envelope == null) return;

    // Cause the progress indicator to appear.
    setState(() => _progress = 0);

    // Create parameters specifying the region to take offline.
    // Provides a min scale to avoid requesting a huge download. Note maxScale defaults to 0.0.
    const minScale = 1e4;
    final parameters =
        await _offlineMapTask.createDefaultGenerateOfflineMapParameters(
      areaOfInterest: envelope,
      minScale: minScale,
    );
    parameters.continueOnErrors = false;

    // Prepare an empty directory to store the offline map.
    final documentsUri = (await getApplicationDocumentsDirectory()).uri;
    final downloadDirectoryUri = documentsUri.resolve('offline_map');
    final downloadDirectory = Directory.fromUri(downloadDirectoryUri);
    if (downloadDirectory.existsSync()) {
      downloadDirectory.deleteSync(recursive: true);
    }
    downloadDirectory.createSync();

    // Create a job to generate the offline map.
    _generateOfflineMapJob = _offlineMapTask.generateOfflineMap(
      parameters: parameters,
      downloadDirectoryUri: downloadDirectoryUri,
    );

    // Listen for progress updates.
    _generateOfflineMapJob!.onProgressChanged.listen((progress) {
      setState(() => _progress = progress);
    });

    try {
      // Run the job.
      final result = await _generateOfflineMapJob!.run();

      // Get the offline map and display it.
      _mapViewController.arcGISMap = result.offlineMap;
      _generateOfflineMapJob = null;
    } catch (e) {
      // If an error happens (such as cancellation), reset state.
      _generateOfflineMapJob = null;
      setState(() => _progress = null);
      return;
    }

    // The job was successful and we are now viewing the offline amp.
    setState(() {
      _progress = null;
      _offline = true;
    });
  }
}