Create and save KML file

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Construct a KML document and save it as a KMZ file.
Image of create and save KML file
Use case

If you need to create and save data on the fly, you can use KML to create points, lines, and polygons by sketching on the map, customizing the style, and serializing them as KML nodes in a KML Document. Once complete, you can share the KML data with others that are using a KML reading application, such as ArcGIS Earth.
How to use the sample

Tap on one of the buttons in the middle row to start adding a geometry. Tap on the map view to place vertices. Tap the "Complete Sketch" button to add the geometry to the KML document as a new KML placemark. Use the style interface to edit the style of the placemark. If you do not wish to set a style, tap the "Don't Apply Style" button. When you are finished adding KML nodes, tap on the "Save KMZ file" button to save the active KML document as a .kmz file on your system. Use the "Reset" button to clear the current KML document and start a new one.
How it works

Create a KmlDocument
Create a KmlDataset using the KmlDocument.
Create a KmlLayer using the KmlDataset and add it to Map.OperationalLayers.
Create Geometry using SketchEditor.
Project that Geometry to WGS84 using GeometryEngine.Project.
Create a KmlGeometry object using that projected Geometry.
Create a KmlPlacemark using the KmlGeometry.
Add the KmlPlacemark to the KmlDocument.
Set the KmlStyle for the KmlPlacemark.
When finished with adding KmlPlacemark nodes to the KmlDocument, save the KmlDocument to a file using the SaveAsAsync method.
Relevant API

GeometryEngine.Project
KmlDataset
KmlDocument
KmlGeometry
KmlLayer
KmlNode.SaveAsASync
KmlPlacemark
KmlStyle
SketchEditor
Sample Code

CreateAndSaveKmlFile.cs
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﻿// Copyright 2019 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.

using ArcGISRuntime;
using Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.Ogc;
using Esri.ArcGISRuntime.UI;
using Esri.ArcGISRuntime.UI.Controls;
using Foundation;
using System;
using System.Collections.Generic;
using System.Drawing;
using System.IO;
using UIKit;

namespace ArcGISRuntimeXamarin.Samples.CreateAndSaveKmlFile
{
    [Register("CreateAndSaveKmlFile")]
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        name: "Create and save KML file",
        category: "Layers",
        description: "Construct a KML document and save it as a KMZ file.",
        instructions: "Tap on one of the buttons in the middle row to start adding a geometry. Tap on the map view to place vertices. Tap the \"Complete Sketch\" button to add the geometry to the KML document as a new KML placemark. Use the style interface to edit the style of the placemark. If you do not wish to set a style, tap the \"Don't Apply Style\" button. When you are finished adding KML nodes, tap on the \"Save KMZ file\" button to save the active KML document as a .kmz file on your system. Use the \"Reset\" button to clear the current KML document and start a new one.",
        tags: new[] { "KML", "KMZ", "Keyhole", "OGC" })]
    public class CreateAndSaveKmlFile : UIViewController
    {
        // Hold references to UI controls.
        private MapView _myMapView;
        private UIToolbar _toolbar;
        private UIBarButtonItem _addButton;
        private UIBarButtonItem _resetButton;
        private UIBarButtonItem _saveButton;
        private UIBarButtonItem _doneButton;
        private UILabel _helpLabel;

        // KML objects
        private KmlDocument _kmlDocument;
        private KmlDataset _kmlDataset;
        private KmlLayer _kmlLayer;
        private KmlPlacemark _currentPlacemark;

        private List<string> _iconLinks;
        private List<UIColor> _colorList;

        public CreateAndSaveKmlFile()
        {
            Title = "Create and save KML file";
        }

        private void Initialize()
        {
            // Create the map.
            _myMapView.Map = new Map(BasemapStyle.ArcGISImageryStandard);

            // Load the KML document.
            ResetKml();

            // Set the links for icons.
            _iconLinks = new List<string>()
            {
                "https://static.arcgis.com/images/Symbols/Shapes/BlueCircleLargeB.png",
                "https://static.arcgis.com/images/Symbols/Shapes/BlueDiamondLargeB.png",
                "https://static.arcgis.com/images/Symbols/Shapes/BluePin1LargeB.png",
                "https://static.arcgis.com/images/Symbols/Shapes/BluePin2LargeB.png",
                "https://static.arcgis.com/images/Symbols/Shapes/BlueSquareLargeB.png",
                "https://static.arcgis.com/images/Symbols/Shapes/BlueStarLargeB.png"
            };

            // Set the colors for the color picker.
            _colorList = new List<UIColor>
            {
                UIColor.Black,UIColor.Blue,UIColor.Brown,UIColor.DarkGray,UIColor.Gray,UIColor.Green,UIColor.Magenta,UIColor.Orange,UIColor.Purple,UIColor.Red,UIColor.Yellow
            };
        }

        private void ResetKml()
        {
            // Clear any existing layers from the map.
            _myMapView.Map.OperationalLayers.Clear();

            // Reset the most recently placed placemark.
            _currentPlacemark = null;

            // Create a new KML document.
            _kmlDocument = new KmlDocument() { Name = "KML Sample Document" };

            // Create a KML dataset using the KML document.
            _kmlDataset = new KmlDataset(_kmlDocument);

            // Create the KML layer using the KML dataset.
            _kmlLayer = new KmlLayer(_kmlDataset);

            // Add the KML layer to the map.
            _myMapView.Map.OperationalLayers.Add(_kmlLayer);
        }

        private void AddClick(object sender, EventArgs e)
        {
            // Decide what type of placemark to add.
            UIAlertController prompt = UIAlertController.Create("Choose a geometry type", null, UIAlertControllerStyle.ActionSheet);
            prompt.AddAction(UIAlertAction.Create("Point", UIAlertActionStyle.Default, AddGeometry));
            prompt.AddAction(UIAlertAction.Create("Polyline", UIAlertActionStyle.Default, AddGeometry));
            prompt.AddAction(UIAlertAction.Create("Polygon", UIAlertActionStyle.Default, AddGeometry));

            // Swap toolbar.
            _toolbar.Items = new[] { _doneButton };

            // Needed to prevent crash on iPad.
            UIPopoverPresentationController ppc = prompt.PopoverPresentationController;
            if (ppc != null)
            {
                ppc.SourceView = _toolbar;
                ppc.PermittedArrowDirections = UIPopoverArrowDirection.Down;
            }

            PresentViewController(prompt, true, null);
        }

        private async void AddGeometry(UIAlertAction obj)
        {
            try
            {
                // Create variables for the sketch creation mode and color.
                SketchCreationMode creationMode;

                // Set the creation mode and UI based on which button called this method.
                switch (obj.Title)
                {
                    case "Point":
                        creationMode = SketchCreationMode.Point;
                        _helpLabel.Text = "Tap to add a point.";
                        break;

                    case "Polyline":
                        creationMode = SketchCreationMode.Polyline;
                        _helpLabel.Text = "Tap to add a vertex.";
                        break;

                    case "Polygon":
                        creationMode = SketchCreationMode.Polygon;
                        _helpLabel.Text = "Tap to add a vertex.";
                        break;

                    default:
                        return;
                }

                // Get the user-drawn geometry.
                Geometry geometry = await _myMapView.SketchEditor.StartAsync(creationMode, true);

                // Project the geometry to WGS84 (WGS84 is required by the KML standard).
                Geometry projectedGeometry = GeometryEngine.Project(geometry, SpatialReferences.Wgs84);

                // Create a KmlGeometry using the new geometry.
                KmlGeometry kmlGeometry = new KmlGeometry(projectedGeometry, KmlAltitudeMode.ClampToGround);

                // Create a new placemark.
                _currentPlacemark = new KmlPlacemark(kmlGeometry);

                // Add the placemark to the KmlDocument.
                _kmlDocument.ChildNodes.Add(_currentPlacemark);

                // Enable the style editing UI.
                ChooseStyle();
            }
            catch (ArgumentException)
            {
                ShowMessage("Error", "Unsupported Geometry");
            }
            finally
            {
                // Re-add toolbar.
                _toolbar.Items = new[]
                {
                    _addButton,
                    new UIBarButtonItem(UIBarButtonSystemItem.FlexibleSpace),
                    _saveButton,
                    _resetButton
                };
                _helpLabel.Text = "";
            }
        }

        private void ChooseStyle()
        {
            // Start the UI for the user choosing the junction.
            if (_currentPlacemark.GraphicType == KmlGraphicType.Point)
            {
                // Build a UI alert controller for picking the icon.
                UIAlertController prompt = UIAlertController.Create(string.Empty, "Choose an icon.", UIAlertControllerStyle.ActionSheet);
                foreach (string link in _iconLinks)
                {
                    UIAlertAction action = UIAlertAction.Create(link, UIAlertActionStyle.Default, Icon_Select);
                    UIImage image = new UIImage(NSData.FromUrl(new NSUrl(link)));
                    action.SetValueForKey(image, new NSString("image"));
                    prompt.AddAction(action);
                }
                prompt.AddAction(UIAlertAction.Create("No Style", UIAlertActionStyle.Cancel, null));

                // Needed to prevent crash on iPad.
                UIPopoverPresentationController ppc = prompt.PopoverPresentationController;
                if (ppc != null)
                {
                    ppc.SourceView = _toolbar;
                    ppc.PermittedArrowDirections = UIPopoverArrowDirection.Down;
                }

                PresentViewController(prompt, true, null);
            }
            else if (_currentPlacemark.GraphicType == KmlGraphicType.Polyline || _currentPlacemark.GraphicType == KmlGraphicType.Polygon)
            {
                // Build a UI alert controller for picking the color.
                UIAlertController prompt = UIAlertController.Create(null, "Choose a color.", UIAlertControllerStyle.ActionSheet);
                foreach (UIColor color in _colorList)
                {
                    UIAlertAction action = UIAlertAction.Create(color.ToString(), UIAlertActionStyle.Default, Color_Select);
                    action.SetValueForKey(color, new NSString("titleTextColor"));
                    prompt.AddAction(action);
                }
                prompt.AddAction(UIAlertAction.Create("No Style", UIAlertActionStyle.Cancel, null));

                // Needed to prevent crash on iPad.
                UIPopoverPresentationController ppc = prompt.PopoverPresentationController;
                if (ppc != null)
                {
                    ppc.SourceView = _toolbar;
                    ppc.PermittedArrowDirections = UIPopoverArrowDirection.Down;
                }

                PresentViewController(prompt, true, null);
            }
        }

        private void Icon_Select(UIAlertAction obj)
        {
            // Get the Uri of the selected action.
            Uri uri = new Uri(obj.Title);

            // Create a style for the placemark.
            _currentPlacemark.Style = new KmlStyle();
            _currentPlacemark.Style.IconStyle = new KmlIconStyle(new KmlIcon(uri), 1.0);
        }

        private void Color_Select(UIAlertAction obj)
        {
            // Convert the UIColor to a System.Drawing.Color
            UIColor uiColor = obj.ValueForKey(new NSString("titleTextColor")) as UIColor;
            nfloat red, green, blue, alpha;
            uiColor.GetRGBA(out red, out green, out blue, out alpha);
            Color color = Color.FromArgb((int)(alpha * 255), (int)(red * 255), (int)(green * 255), (int)(blue * 255));

            // Create a style for the placemark.
            _currentPlacemark.Style = new KmlStyle();

            if (_currentPlacemark.GraphicType == KmlGraphicType.Polyline)
            {
                _currentPlacemark.Style.LineStyle = new KmlLineStyle(color, 8);
            }
            else if (_currentPlacemark.GraphicType == KmlGraphicType.Polygon)
            {
                _currentPlacemark.Style.PolygonStyle = new KmlPolygonStyle(color);
                _currentPlacemark.Style.PolygonStyle.IsFilled = true;
                _currentPlacemark.Style.PolygonStyle.IsOutlined = false;
            }
        }

        private void DoneClick(object sender, EventArgs e)
        {
            try
            {
                // Finish the sketch.
                _myMapView.SketchEditor.CompleteCommand.Execute(null);
            }
            catch (ArgumentException)
            {
            }
        }

        private void Reset_Click(object sender, EventArgs e)
        {
            ResetKml();
        }

        private async void Save_Click(object sender, EventArgs e)
        {
            try
            {
                string offlineDataFolder = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);

                // If temporary data folder doesn't exists, create it.
                if (!Directory.Exists(offlineDataFolder))
                {
                    Directory.CreateDirectory(offlineDataFolder);
                }

                string path = Path.Combine(offlineDataFolder, "sampledata.kmz");
                using (Stream stream = new FileStream(path, FileMode.OpenOrCreate, FileAccess.Write, FileShare.None))
                {
                    // Write the KML document to the stream of the file.
                    await _kmlDocument.WriteToAsync(stream);
                }
                ShowMessage("Success", "File saved locally.");
            }
            catch (Exception)
            {
                ShowMessage("Error", "File not saved.");
            }
        }

        private void ShowMessage(string title, string message)
        {
            // Create alert for the user.
            UIAlertController alert = UIAlertController.Create(title, message, UIAlertControllerStyle.Alert);
            alert.AddAction(UIAlertAction.Create("OK", UIAlertActionStyle.Default, null));
            PresentViewController(alert, true, null);
        }

        public override void LoadView()
        {
            // Create the views.
            View = new UIView { BackgroundColor = ApplicationTheme.BackgroundColor };

            _myMapView = new MapView();
            _myMapView.TranslatesAutoresizingMaskIntoConstraints = false;

            _addButton = new UIBarButtonItem(UIBarButtonSystemItem.Add);
            _doneButton = new UIBarButtonItem(UIBarButtonSystemItem.Done);

            _saveButton = new UIBarButtonItem();
            _saveButton.Title = "Save";

            _resetButton = new UIBarButtonItem();
            _resetButton.Title = "Reset";

            _toolbar = new UIToolbar();
            _toolbar.TranslatesAutoresizingMaskIntoConstraints = false;
            _toolbar.Items = new[]
            {
                _addButton,
                new UIBarButtonItem(UIBarButtonSystemItem.FlexibleSpace),
                _saveButton,
                _resetButton
            };

            _helpLabel = new UILabel
            {
                Text = "Press the '+' button to start.",
                AdjustsFontSizeToFitWidth = true,
                TextAlignment = UITextAlignment.Center,
                BackgroundColor = UIColor.FromWhiteAlpha(0, .6f),
                TextColor = UIColor.White,
                Lines = 1,
                TranslatesAutoresizingMaskIntoConstraints = false
            };

            // Add the views.
            View.AddSubviews(_myMapView, _toolbar, _helpLabel);

            // Lay out the views.
            NSLayoutConstraint.ActivateConstraints(new[]
            {
                _myMapView.TopAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.TopAnchor),
                _myMapView.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
                _myMapView.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor),
                _myMapView.BottomAnchor.ConstraintEqualTo(_toolbar.TopAnchor),

                _toolbar.BottomAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.BottomAnchor),
                _toolbar.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
                _toolbar.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor),

                _helpLabel.TopAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.TopAnchor),
                _helpLabel.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
                _helpLabel.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor),
                _helpLabel.HeightAnchor.ConstraintEqualTo(25)
            });
        }

        public override void ViewDidLoad()
        {
            base.ViewDidLoad();
            Initialize();
        }

        public override void ViewWillAppear(bool animated)
        {
            base.ViewWillAppear(animated);

            // Subscribe to events.
            _addButton.Clicked += AddClick;
            _doneButton.Clicked += DoneClick;
            _saveButton.Clicked += Save_Click;
            _resetButton.Clicked += Reset_Click;
        }

        public override void ViewDidDisappear(bool animated)
        {
            base.ViewDidDisappear(animated);

            // Unsubscribe from events, per best practice.
            _addButton.Clicked -= AddClick;
            _doneButton.Clicked -= DoneClick;
            _saveButton.Clicked -= Save_Click;
            _resetButton.Clicked -= Reset_Click;
        }
    }
}