Change viewpoint

This sample demonstrates different ways in which you can change the viewpoint or visible area of the map.

Change viewpoint


Click any of the available buttons to change the current viewpoint


// Copyright 2016 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:
// 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.Controls;
using Foundation;
using System;
using System.Collections.Generic;
using System.Linq;
using UIKit;

namespace ArcGISRuntimeXamarin.Samples.ChangeViewpoint
    public class ChangeViewpoint : UIViewController
        // Constant holding offset where the MapView control should start
        private const int yPageOffset = 60;

        private UIButton _viewpointsButton;

        // Create and hold reference to the used MapView
        private MapView _myMapView = new MapView();

        // Coordinates for London
        private MapPoint LondonCoords = new MapPoint(
            -13881.7678417696, 6710726.57374296, SpatialReferences.WebMercator);
        private double LondonScale = 8762.7156655228955;

        // Coordinates for Redlands
        private Polygon RedlandsEnvelope = new Polygon(
            new List<MapPoint>
                    new MapPoint(-13049785.1566222, 4032064.6003424),
                    new MapPoint(-13049785.1566222, 4040202.42595729),
                    new MapPoint(-13037033.5780234, 4032064.6003424),
                    new MapPoint(-13037033.5780234, 4040202.42595729)

        // Coordinates for Edinburgh
        private Polygon EdinburghEnvelope = new Polygon(
            new List<MapPoint>
                new MapPoint(-354262.156621384, 7548092.94093301),
                new MapPoint(-354262.156621384, 7548901.50684376),
                new MapPoint(-353039.164455303, 7548092.94093301),
                new MapPoint(-353039.164455303, 7548901.50684376)},

        // String array to store titles for the viewpoints specified above.
        private string[] titles = new string[]
            "Center & Scale",

        public ChangeViewpoint()
            Title = "Change viewpoint";
        public override void ViewDidLoad()

            // Create the UI, setup the control references and execute initialization 

        public override void ViewDidLayoutSubviews()
            // Setup the visual frame for the MapView
            _myMapView.Frame = new CoreGraphics.CGRect(0, 0, View.Bounds.Width, View.Bounds.Height);

            // Setup the visual frame for the Button
            _viewpointsButton.Frame = new CoreGraphics.CGRect(0, View.Bounds.Height - 40, View.Bounds.Width, 40);


        private void Initialize()
            // Create new Map with basemap and initial location
            Map myMap = new Map(Basemap.CreateTopographic());

            // Assign the map to the MapView
            _myMapView.Map = myMap;

        private void OnViewpointsButtonTouch(object sender, EventArgs e)
            // Initialize an UIAlertController
            UIAlertController viewpointAlert = UIAlertController.Create(
                "Select viewpoint", "", UIAlertControllerStyle.Alert);

            // Add actions to alert. Selecting an option set the new viewpoint
            viewpointAlert.AddAction(UIAlertAction.Create(titles[0], UIAlertActionStyle.Default, 
                async (action) =>
                    // Set Viewpoint using Redlands envelope defined above and a padding of 20
                    await _myMapView.SetViewpointGeometryAsync(RedlandsEnvelope, 20);
            viewpointAlert.AddAction(UIAlertAction.Create(titles[1], UIAlertActionStyle.Default, 
                async (action) =>
                    // Set Viewpoint so that it is centered on the London coordinates defined above
                    await _myMapView.SetViewpointCenterAsync(LondonCoords);
                    // Set the Viewpoint scale to match the specified scale 
                    await _myMapView.SetViewpointScaleAsync(LondonScale);
            viewpointAlert.AddAction(UIAlertAction.Create(titles[2], UIAlertActionStyle.Default, 
                async (action) =>
                    // Navigate to full extent of the first baselayer before animating to specified geometry
                    await _myMapView.SetViewpointAsync(
                        new Viewpoint(_myMapView.Map.Basemap.BaseLayers.First().FullExtent));
                    // Create a new Viewpoint using the specified geometry
                    var viewpoint = new Viewpoint(EdinburghEnvelope);
                    // Set Viewpoint of MapView to the Viewpoint created above and animate to it using a timespan of 5 seconds
                    await _myMapView.SetViewpointAsync(viewpoint, TimeSpan.FromSeconds(5));
            PresentViewController(viewpointAlert, true, null);

        private void CreateLayout()
            // Add a button at the bottom to show viewpoint choices
            _viewpointsButton = new UIButton(UIButtonType.Custom)
                BackgroundColor = UIColor.White

            // Create button to show map options
            _viewpointsButton.SetTitle("Viewpoints", UIControlState.Normal);
            _viewpointsButton.SetTitleColor(UIColor.Blue, UIControlState.Normal);
            _viewpointsButton.TouchUpInside += OnViewpointsButtonTouch;

            // Add MapView to the page
            View.AddSubviews(_myMapView, _viewpointsButton);

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