Location of Windows 8 Metro

Document directory

• 1. Overview
• 2. Guidelines
• 3. C # example

1. Overview

• There are four Geographic Positioning Methods: WiFi, IP address, mobile phone base station, and GPS.

• Win8 has built-in WiFi, IP address two methods, WiFi positioning accuracy is about 350 meters, IP address precision is 25 km.

• The Win8 positioning service does not provide orientation, height, speed, address, and other data.

• When you need to use the location service, you need to explicitly remind the user and enable the location service in the privacy settings of window8.

• Enable the location service in the application capability.

2. Guidelines

• Only one request for positioning is called.Getgeopostionasync() Method.

• Set the trajectory data change threshold by settingMovementthresholdAttribute, triggered only when the value changes beyond the range of this valuePositionchangedEvents, such as weather changes between cities.

• Set the location data report frequency by settingReportintervalProperty. If the value is 0, it changes in real time. Note: Some devices may be useless to set this attribute.

• Set the precision by settingDesiredaccuracyProperty. GPS is called only when the precision is high.

• Startup delay, which may take 2 seconds. Do not block the UI.

• Run in the background. When an application is suspended, data will not be updated. Therefore, consider running in the background.

• CaptureStatuschangedEvent to understand the available status of the location service.
• When the location service is disabledGetgeopostionasync() An exception will be reported,LocationstatusIf the value is disable, you must be reminded to enable the location service.
• Cache data should be cleared when the status is unavailable.
• When you enable the location function again, no event is generated. You can only obtain the event by requesting data from the program.
• When an application is suspended to activated, it must obtain location data again.
• A refresh button is provided to allow users to obtain location data again.
• We recommend that you prompt "your location is currently turned off. Change your settings through the settings charm to turn it back on ."
• If the location is not important information, use the notification. If the location is important information, such as a map, use flyout.

3. C # example

Obtain location data

using System;using System.Collection.Generic;using System.Linq;using System.Threading.Tasks;using Windows.Foundation;using Windows.UI.DirectUI;using Windows.UI.DirectUI.Controls;using Windows.UI.DirectUI.Data;using Windows.Devices.Geolocation;namespace GeolocationSample{    partial class MainPage    {        Geolocator geo = null;        public MainPage()        {            InitializeComponent();        }                private async void button1_Click(            object sender, RoutedEventArgs e)        {            if (geo == null)            {                geo = new Geolocator();            }                        IGeoposition pos = await geo.GetGeopositionAsync();                        textblockLatitude.Text = "Latitude: " + pos.Coordinate.Latitude.ToString();            textblockLongitude.Text = "Longitude: " + pos.Coordinate.Longitude.ToString();            textblockAccuracy.Text = "Accuracy: " + pos.Coordinate.Accuracy.ToString();        }    }}

 

Obtain location change data

using System;using System.Collection.Generic;using System.Linq;using System.Threading.Tasks;using Windows.Foundation;using Windows.UI.Core;using Windows.UI.DirectUI;using Windows.UI.DirectUI.Controls;using Windows.UI.DirectUI.Data;using Windows.Devices.Geolocation; namespace GeolocationEventsSample{    partial class MainPage    {        private Geolocator geo = null;        private CoreDispatcher _cd;         public MainPage()        {            InitializeComponent();            _cd = Window.Current.CoreWindow.Dispatcher;        }                private void button1_Click(object sender, RoutedEventArgs e)        {            if (geo == null)            {                geo = new Geolocator();            }            if (geo != null)            {                geo.PositionChanged +=                     new TypedEventHandler<Geolocator,                        PositionChangedEventArgs>(geo_PositionChanged);            }        }             private void button2_Click(object sender, RoutedEventArgs e)     {         if (geo != null)         {             geo.PositionChanged -= new TypedEventHandler<Geolocator, PositionChangedEventArgs> (geo_PositionChanged);         }     }            private void geo_PositionChanged(Geolocator sender, PositionChangedEventArgs e)     {         _cd.InvokeAsync(CoreDispatcherPriority.Normal, (s, a) =>         {             IGeoposition pos = (a.Context as IPositionChangedEventArgs).Position;             textLatitude.Text = "Latitude: " + pos.Coordinate.Latitude.ToString();             textLongitude.Text = "Longitude: " + pos.Coordinate.Longitude.ToString();             textAccuracy.Text = "Accuracy: " + pos.Coordinate.Accuracy.ToString();          }, this, e);     }   }}

 

Set the location data change threshold

using System;using System.Collections.Generic;using System.IO;using System.Linq;using Windows.Foundation;using Windows.Foundation.Collections;using Windows.UI.Xaml;using Windows.UI.Xaml.Controls;using Windows.UI.Xaml.Controls.Primitives;using Windows.UI.Xaml.Data;using Windows.UI.Xaml.Input;using Windows.UI.Xaml.Media;using Windows.UI.Xaml.Navigation;using Windows.UI.Core;using Windows.Devices.Geolocation;// The Blank Page item template is documented at http://go.microsoft.com/fwlink/?LinkId=234238namespace GeolocationAdjustDistance{    /// <summary>    /// An empty page that can be used on its own or navigated to within a Frame.    /// </summary>    public sealed partial class BlankPage : Page    {        private Geolocator geo = null;        private CoreDispatcher _cd;        private double prevLatitude = -1;        private double prevLongitude = -1;        private double totalDistance = 0;        public BlankPage()        {            this.InitializeComponent();            _cd = Window.Current.CoreWindow.Dispatcher;        }        /// <summary>        /// Invoked when this page is about to be displayed in a Frame.        /// </summary>        /// <param name="e">Event data that describes how this page was reached.  The Parameter        /// property is typically used to configure the page.</param>        protected override void OnNavigatedTo(NavigationEventArgs e)        {        }        private void Button_Click_1(object sender, RoutedEventArgs e)        {            if (geo == null)            {                geo = new Geolocator();            }            if (geo != null)            {                geo.PositionChanged += new TypedEventHandler<Geolocator,                    PositionChangedEventArgs>(geo_PositionChanged);                geo.StatusChanged += new TypedEventHandler<Geolocator,                    StatusChangedEventArgs>(geo_StatusChanged);                geo.MovementThreshold = float.Parse(tbThreshold.Text);                tbThreshold.IsEnabled = false;                TextBox1.Text = "Tracking Started " +                                 "(Time, Latitude, Longitude, Distance)\n";            }        }        private void Button_Click_2(object sender, RoutedEventArgs e)        {            if (geo != null)            {                geo.PositionChanged -= new TypedEventHandler<Geolocator,                    PositionChangedEventArgs>(geo_PositionChanged);                geo.StatusChanged -= new TypedEventHandler<Geolocator,                     StatusChangedEventArgs>(geo_StatusChanged);                TextBox1.Text += "\nTracking Stopped.\n" +                                 "Total Distance recorded: " +                                 totalDistance.ToString("F2") + " m\n";                tbThreshold.IsEnabled = true;            }        }        private double CalculateDistance(double prevLat, double prevLong, double currLat, double currLong)        {            const double degreesToRadians = (Math.PI / 180.0);            const double earthRadius = 6371; // kilometers            // convert latitude and longitude values to radians            var prevRadLat = prevLat * degreesToRadians;            var prevRadLong = prevLong * degreesToRadians;            var currRadLat = currLat * degreesToRadians;            var currRadLong = currLong * degreesToRadians;            // calculate radian delta between each position.            var radDeltaLat = currRadLat - prevRadLat;            var radDeltaLong = currRadLong - prevRadLong;            // calculate distance            var expr1 = (Math.Sin(radDeltaLat / 2.0) *                         Math.Sin(radDeltaLat / 2.0)) +                        (Math.Cos(prevRadLat) *                          Math.Cos(currRadLat) *                         Math.Sin(radDeltaLong / 2.0) *                          Math.Sin(radDeltaLong / 2.0));            var expr2 = 2.0 * Math.Atan2(Math.Sqrt(expr1),                                          Math.Sqrt(1 - expr1));            var distance = (earthRadius * expr2);             return distance * 1000;  // return results as meters        }        void geo_PositionChanged(Geolocator sender, PositionChangedEventArgs args)        {            _cd.InvokeAsync(CoreDispatcherPriority.Normal, (s, a) =>            {                Geoposition pos = (a.Context as IPositionChangedEventArgs).Position;                double updateDistance = 0;                // Calculate distance;                if ( ( prevLatitude == -1 ) || ( prevLongitude == -1 ) )                 {                   updateDistance = 0;                } else {                   updateDistance = CalculateDistance( prevLatitude, prevLongitude,                       pos.Coordinate.Latitude, pos.Coordinate.Longitude );                }               // Update tracking               prevLatitude = pos.Coordinate.Latitude;               prevLongitude = pos.Coordinate.Longitude;               totalDistance += updateDistance;               // display the results.               TextBox1.Text += "Position Update: " +                                pos.Coordinate.Timestamp.ToString("T") + ", " +                                pos.Coordinate.Latitude.ToString("F3") + ", " +                                pos.Coordinate.Longitude.ToString("F3") + ", " +                                updateDistance.ToString("F2") + " m\n";            }, this, args);        }        void geo_StatusChanged(Geolocator sender, StatusChangedEventArgs args)        {            var newStatus = args.Status;            var strStatus = "";            switch (newStatus)            {                case PositionStatus.Ready:                     strStatus = "Location is available.";                    break;                case PositionStatus.Initializing:                    strStatus = "Geolocation service is initializing.";                    break;                case PositionStatus.NoData:                    strStatus = "Location service data is not available.";                    break;                case PositionStatus.Disabled:                    strStatus = "Location services are disabled. Use the " +                                "Settings charm to enable them.";                    break;                case PositionStatus.NotInitialized:                    strStatus = "Location status is not initialized because " +                                "the app has not yet requested location data.";                    break;                case PositionStatus.NotAvailable:                    strStatus = "Location services are not supported on your system.";                    break;                default:                    strStatus = "Unknown PositionStatus value (" +                                 newStatus.ToString() + ").";                    break;            }            _cd.InvokeAsync(CoreDispatcherPriority.Normal, (s, a) =>            {               TextBox1.Text += strStatus + "\n";            }, this, args);        }    }}