Show callout

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Show a callout with the latitude and longitude of user-tapped points.

Image of show callout

Use case

Callouts are used to display temporary detail content on a map. You can display text and arbitrary UI controls in callouts.

How to use the sample

Tap anywhere on the map. A callout showing the WGS84 coordinates for the tapped point will appear.

How it works

  1. Listen for GeoViewTapped events on the map view.
  2. When the user taps, get the tapped location from the Location property of the GeoViewInputEventArgs.
  3. Project the geometry to WGS84 using GeometryEngine.Project.
  4. Create a string to display the coordinates; note that latitude and longitude in WGS84 map to the Y and X coordinates.
  5. Create a new callout definition using a title and the coordinate string.
  6. Display the callout by calling ShowCalloutAt on the map view with the location and the callout definition.

Relevant API

  • CalloutDefinition
  • GeometryEngine.Project
  • GeoViewTappedEventArgs
  • MapView.GeoViewTapped
  • MapView.ShowCalloutAt

Tags

balloon, bubble, callout, flyout, flyover, info window, popup, tap

Sample Code

ShowCallout.cs
                                                                                                                       
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// Copyright 2017 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 Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.UI;
using Esri.ArcGISRuntime.UI.Controls;
using Foundation;
using UIKit;

namespace ArcGISRuntime.Samples.ShowCallout
{
    [Register("ShowCallout")]
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        name: "Show callout",
        category: "MapView",
        description: "Show a callout with the latitude and longitude of user-tapped points.",
        instructions: "Tap anywhere on the map. A callout showing the WGS84 coordinates for the tapped point will appear.",
        tags: new[] { "balloon", "bubble", "callout", "flyout", "flyover", "info window", "popup", "tap" })]
    public class ShowCallout : UIViewController
    {
        // Hold references to UI controls.
        private MapView _myMapView;

        public ShowCallout()
        {
            Title = "Show callout";
        }

        private void Initialize()
        {
            // Show a streets basemap.
            _myMapView.Map = new Map(BasemapStyle.ArcGISStreets);
        }

        private void MapView_GeoViewTapped(object sender, GeoViewInputEventArgs e)
        {
            // Get the user-tapped location.
            MapPoint mapLocation = e.Location;

            // Project the map point to WGS84 for latitude/longitude display.
            MapPoint projectedLocation = (MapPoint) GeometryEngine.Project(mapLocation, SpatialReferences.Wgs84);

            // Format the display callout string based upon the projected map point (example: "Lat: 100.123, Long: 100.234").
            string mapLocationDescription = $"Lat: {projectedLocation.Y:F3} Long:{projectedLocation.X:F3}";

            // Create a new callout definition using the formatted string.
            CalloutDefinition myCalloutDefinition = new CalloutDefinition("Location:", mapLocationDescription);

            // Display the callout.
            _myMapView.ShowCalloutAt(mapLocation, myCalloutDefinition);
        }

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

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

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

            UILabel helpLabel = new UILabel
            {
                Text = "Tap to show a callout.",
                AdjustsFontSizeToFitWidth = true,
                TextAlignment = UITextAlignment.Center,
                BackgroundColor = UIColor.FromWhiteAlpha(0, .6f),
                TextColor = UIColor.White,
                Lines = 1,
                TranslatesAutoresizingMaskIntoConstraints = false
            };

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

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

                helpLabel.TopAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.TopAnchor),
                helpLabel.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
                helpLabel.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor),
                helpLabel.HeightAnchor.ConstraintEqualTo(40)
            });
        }

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

            // Subscribe to events.
            _myMapView.GeoViewTapped += MapView_GeoViewTapped;
        }

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

            // Unsubscribe from events, per best practice.
            _myMapView.GeoViewTapped -= MapView_GeoViewTapped;
        }
    }
}

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