Group layers

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Group a collection of layers together and toggle their visibility as a group.

Image of group layers

Use case

Group layers communicate to the user that layers are related and can be managed together.

In a land development project, you might group layers according to the phase of development.

How to use the sample

The layers in the map will be displayed in a table of contents. Toggle the checkbox next to a layer's name to change its visibility. Turning a group layer's visibility off will override the visibility of its child layers.

How it works

NOTE See WPF for an example of using a TreeView with a hierarchical data template.

  1. Create an empty GroupLayer.
  2. Add a child layer to the group layer's layers collection.
  3. To build the table of contents, use a TreeView with a HierarchicalDataTemplate.
  4. To toggle the visibility of the group, change the group layer's visibility property.

Relevant API

  • GroupLayer
  • ILayerContent

Additional information

The full extent of a group layer may change when child layers are added/removed. Group layers do not have a spatial reference, but the full extent will have the spatial reference of the first child layer.

Group layers can be saved to web scenes. In web maps, group layers will be ignored.

Tags

group layer, layers

Sample Code

GroupLayers.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.Mapping;
using Esri.ArcGISRuntime.UI.Controls;
using Foundation;
using System;
using System.Linq;
using System.Threading.Tasks;
using UIKit;

namespace ArcGISRuntimeXamarin.Samples.GroupLayers
{
    [Register("GroupLayers")]
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        name: "Group layers",
        category: "Layers",
        description: "Group a collection of layers together and toggle their visibility as a group.",
        instructions: "The layers in the map will be displayed in a table of contents. Toggle the checkbox next to a layer's name to change its visibility. Turning a group layer's visibility off will override the visibility of its child layers.",
        tags: new[] { "group layer", "layers" })]
    public class GroupLayers : UIViewController
    {
        // Hold references to UI controls.
        private SceneView _mySceneView;
        private UIScrollView _layerContainerView;
        private UIStackView _layerStackView;
        private NSLayoutConstraint[] _verticalConstraints;
        private NSLayoutConstraint[] _horizontalConstraints;

        public GroupLayers()
        {
            Title = "Group layers";
        }

        private async void Initialize()
        {
            // Create the layers.
            ArcGISSceneLayer devOne = new ArcGISSceneLayer(new Uri("https://tiles.arcgis.com/tiles/P3ePLMYs2RVChkJx/arcgis/rest/services/DevA_Trees/SceneServer"));
            FeatureLayer devTwo = new FeatureLayer(new Uri("https://services.arcgis.com/P3ePLMYs2RVChkJx/arcgis/rest/services/DevA_Pathways/FeatureServer/1"));
            ArcGISSceneLayer devThree = new ArcGISSceneLayer(new Uri("https://tiles.arcgis.com/tiles/P3ePLMYs2RVChkJx/arcgis/rest/services/DevB_BuildingShells/SceneServer"));
            ArcGISSceneLayer nonDevOne = new ArcGISSceneLayer(new Uri("https://tiles.arcgis.com/tiles/P3ePLMYs2RVChkJx/arcgis/rest/services/DevA_BuildingShells/SceneServer"));
            FeatureLayer nonDevTwo = new FeatureLayer(new Uri("https://services.arcgis.com/P3ePLMYs2RVChkJx/arcgis/rest/services/DevelopmentProjectArea/FeatureServer/0"));

            // Create the group layer and add sublayers.
            GroupLayer gLayer = new GroupLayer();
            gLayer.Name = "Group: Dev A";
            gLayer.Layers.Add(devOne);
            gLayer.Layers.Add(devTwo);
            gLayer.Layers.Add(devThree);

            // Create the scene with a basemap.
            _mySceneView.Scene = new Scene(BasemapStyle.ArcGISImageryStandard);

            // Add the top-level layers to the scene.
            _mySceneView.Scene.OperationalLayers.Add(gLayer);
            _mySceneView.Scene.OperationalLayers.Add(nonDevOne);
            _mySceneView.Scene.OperationalLayers.Add(nonDevTwo);

            // Wait for all of the layers in the group layer to load.
            await Task.WhenAll(gLayer.Layers.ToList().Select(m => m.LoadAsync()).ToList());

            // Zoom to the extent of the group layer.
            _mySceneView.SetViewpoint(new Viewpoint(gLayer.FullExtent));

            // Add the layer list to the UI.
            foreach (Layer layer in _mySceneView.Scene.OperationalLayers)
            {
                AddLayersToUI(layer);
            }
        }

        private async void AddLayersToUI(Layer layer, int nestLevel = 0)
        {
            // Wait for the layers to load - ensures that the UI will be up-to-date.
            await layer.LoadAsync();

            // Add a row for the current layer.
            _layerStackView.AddArrangedSubview(ViewForLayer(layer, nestLevel));

            // Add rows for any children of this layer if it is a group layer.
            if (layer is GroupLayer layerGroup)
            {
                foreach (Layer child in layerGroup.Layers)
                {
                    AddLayersToUI(child, nestLevel + 1);
                }
            }
        }

        private UIView ViewForLayer(Layer layer, int nestLevel = 0)
        {
            // Create the view that holds the row.
            UIView rowContainer = new UIView();
            rowContainer.TranslatesAutoresizingMaskIntoConstraints = false;

            // Create and configure the visibility toggle.
            UISwitch toggleSwitch = new UISwitch();
            toggleSwitch.TranslatesAutoresizingMaskIntoConstraints = false;
            toggleSwitch.On = true;
            toggleSwitch.ValueChanged += (sender, args) => layer.IsVisible = !layer.IsVisible;

            // Create and configure the label.
            UILabel nameLabel = new UILabel();
            nameLabel.TranslatesAutoresizingMaskIntoConstraints = false;
            nameLabel.Text = layer.Name;

            // Add the views to the row.
            rowContainer.AddSubviews(toggleSwitch, nameLabel);

            // Lay out the views.
            NSLayoutConstraint.ActivateConstraints(new[]
            {
                // Constant implements nesting/hierarchy display.
                toggleSwitch.LeadingAnchor.ConstraintEqualTo(rowContainer.LeadingAnchor, 8 + nestLevel * toggleSwitch.IntrinsicContentSize.Width),
                toggleSwitch.CenterYAnchor.ConstraintEqualTo(rowContainer.CenterYAnchor),
                nameLabel.LeadingAnchor.ConstraintEqualTo(toggleSwitch.TrailingAnchor, 8),
                nameLabel.TrailingAnchor.ConstraintEqualTo(rowContainer.TrailingAnchor),
                nameLabel.CenterYAnchor.ConstraintEqualTo(rowContainer.CenterYAnchor),
                rowContainer.HeightAnchor.ConstraintEqualTo(40)
            });

            return rowContainer;
        }

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

            _mySceneView = new SceneView();
            _mySceneView.TranslatesAutoresizingMaskIntoConstraints = false;

            _layerContainerView = new UIScrollView();
            _layerContainerView.TranslatesAutoresizingMaskIntoConstraints = false;
            _layerContainerView.BackgroundColor = ApplicationTheme.BackgroundColor;

            _layerStackView = new UIStackView();
            _layerStackView.TranslatesAutoresizingMaskIntoConstraints = false;
            _layerStackView.Axis = UILayoutConstraintAxis.Vertical;
            _layerContainerView.AddSubview(_layerStackView);

            // Add the views.
            View.AddSubviews(_mySceneView, _layerContainerView);

            // Lay out the views.
            _verticalConstraints = new[]
            {
                _layerContainerView.TopAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.TopAnchor),
                _layerContainerView.LeadingAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.LeadingAnchor),
                _layerContainerView.TrailingAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.TrailingAnchor),
                _layerContainerView.HeightAnchor.ConstraintEqualTo(6 * 40),
                _mySceneView.TopAnchor.ConstraintEqualTo(_layerContainerView.BottomAnchor),
                _mySceneView.BottomAnchor.ConstraintEqualTo(View.BottomAnchor),
                _mySceneView.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
                _mySceneView.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor),
                _layerStackView.WidthAnchor.ConstraintEqualTo(_layerContainerView.WidthAnchor)
            };
            _horizontalConstraints = new[]
            {
                _layerContainerView.TopAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.TopAnchor),
                _layerContainerView.LeadingAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.LeadingAnchor),
                _layerContainerView.BottomAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.BottomAnchor),
                _layerContainerView.TrailingAnchor.ConstraintEqualTo(_mySceneView.LeadingAnchor),
                _layerContainerView.TrailingAnchor.ConstraintEqualTo(View.CenterXAnchor),
                _mySceneView.TopAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.TopAnchor),
                _mySceneView.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor),
                _mySceneView.BottomAnchor.ConstraintEqualTo(View.BottomAnchor),
                _layerStackView.WidthAnchor.ConstraintEqualTo(_layerContainerView.WidthAnchor)
            };

            ApplyConstraints();
        }

        public override void TraitCollectionDidChange(UITraitCollection previousTraitCollection)
        {
            base.TraitCollectionDidChange(previousTraitCollection);
            ApplyConstraints();
        }

        private void ApplyConstraints()
        {
            NSLayoutConstraint.DeactivateConstraints(_horizontalConstraints);
            NSLayoutConstraint.DeactivateConstraints(_verticalConstraints);

            if (View.TraitCollection.VerticalSizeClass == UIUserInterfaceSizeClass.Compact)
            {
                NSLayoutConstraint.ActivateConstraints(_horizontalConstraints);
            }
            else
            {
                NSLayoutConstraint.ActivateConstraints(_verticalConstraints);
            }
        }

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

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