缩小时位置点会改变

Question

I am developing an windows phone application and have to mark the current location and the destinated location location.But the problem is when the application shows the point normally it shows the correct point but while zooming out , the point's position keeps changing .Below is the code

public partial class Findcar : PhoneApplicationPage
{
    //private static string baseUri = "bingmaps:?";
    DbHelper Db_helper = new DbHelper();
    int ids = 0;
    historyTableSQlite lists = new historyTableSQlite();
    //historyTableSQlite list2 = new historyTableSQlite();

    public static double lt {get; set;}
    public static double lg { get; set; }
    public static double lt2 { get; set; }
    public static double lg2 { get; set; }

    //String fl = Checkin.Floor_st;
    //String zo = Checkin.Zone_st;


    GeoCoordinate currentLocation = null;
    UCCustomToolTip _tooltip = new UCCustomToolTip();
    Geolocator myGeolocator = new Geolocator();

    public Findcar()
    {

        InitializeComponent();
        GetLocation();




    }

    protected override void OnNavigatedTo(NavigationEventArgs e)
    {


        lists = Db_helper.Readlats(lists.Id);
        //list2 = Db_helper.ReadContact(History.Selected_HistoryId);

        lt = lists.latitude;

        lg = lists.longtitude;


        if (lt2 != 0.0D && lg2 != 0.0D)
        {
            lt = lt2;
            lg = lg2;

        }


        // Selected_HistoryId = int.Parse(NavigationContext.QueryString["SelectedHistoryID"]);
    }
    private async void GetLocation()
    {
        // Get current location.

        Geoposition myGeoposition = await myGeolocator.GetGeopositionAsync(maximumAge: TimeSpan.FromMinutes(5), timeout: TimeSpan.FromSeconds(10));
        Geocoordinate myGeocoordinate = myGeoposition.Coordinate;

        currentLocation = CoordinateConverter.ConvertGeocoordinate(myGeocoordinate);
        MapDisplay(currentLocation);

    }

    private void MapDisplay(GeoCoordinate LocationsData)
    {

        ReverseGeocodeQuery Query = new ReverseGeocodeQuery()
        {
            GeoCoordinate = new GeoCoordinate(LocationsData.Latitude, LocationsData.Longitude)
        };
        Query.QueryCompleted += Query_QueryCompleted;
        Query.QueryAsync();


        MapOverlay mylocationOverlay = new MapOverlay();
        mylocationOverlay.Content = _tooltip;
        mylocationOverlay.GeoCoordinate = LocationsData;
        MapLayer myLocationLayer = new MapLayer();
        myLocationLayer.Add(mylocationOverlay);
        mymap.Layers.Add(myLocationLayer);
        mymap.Center = LocationsData;

    }

    void Query_QueryCompleted(object sender, QueryCompletedEventArgs<IList<MapLocation>> e)
    {
        _tooltip.Description = "";
        StringBuilder _description = new StringBuilder();
        foreach (var item in e.Result)
        {
            if (!(item.Information.Address.BuildingName == ""))
            {
                _description.Append(item.Information.Address.BuildingName + ", ");

            }
            if (!(item.Information.Address.BuildingFloor == ""))
            {
                _description.Append(item.Information.Address.BuildingFloor + ", ");

            }
            if (!(item.Information.Address.Street == ""))
            {
                _description.Append(item.Information.Address.Street + ", ");

            }
            if (!(item.Information.Address.District == ""))
            {
                _description.Append(item.Information.Address.District + ",");

            }
            if (!(item.Information.Address.City == ""))
            {
                _description.Append(item.Information.Address.City + ", ");

            }
            if (!(item.Information.Address.State == ""))
            {
                _description.Append(item.Information.Address.State + ", ");

            }
            if (!(item.Information.Address.Street == ""))
            {
                _description.Append(item.Information.Address.Street + ", ");

            }
            if (!(item.Information.Address.Country == ""))
            {
                _description.Append(item.Information.Address.Country + ", ");

            }

            if (!(item.Information.Address.Province == ""))
            {
                _description.Append(item.Information.Address.Province + ", ");

            }
            if (!(item.Information.Address.PostalCode == ""))
            {
                _description.Append(item.Information.Address.PostalCode);

            }

            _tooltip.Description = "Your car :"+_description.ToString();
            _tooltip.FillDescription();
            break;
        }


    }

    private async void TextBlock_Tap(object sender, System.Windows.Input.GestureEventArgs e)
    {

         Geoposition myGeoposition = await myGeolocator.GetGeopositionAsync(maximumAge: TimeSpan.FromMinutes(5), timeout: TimeSpan.FromSeconds(10));
        BingMapsDirectionsTask bing = new BingMapsDirectionsTask()
        {
            //Giving label and coordinates to starting and ending points. 

            Start = new LabeledMapLocation("You are here", new GeoCoordinate(myGeoposition.Coordinate.Latitude, myGeoposition.Coordinate.Longitude)),


            //This is the place where I want to get the latitude and longtitude from the database
            End = new LabeledMapLocation("Your car", new GeoCoordinate(Findcar.lt, Findcar.lg))
        };
        // Launching Bing Maps Direction Tasks
        bing.Show();
    }

    }

Below here is the another class regarding coordinates

public static GeoCoordinate ConvertGeocoordinate(Geocoordinate geocoordinate)
    {
        //historyTableSQlite lists = new historyTableSQlite();
        //DbHelper Db_helper = new DbHelper();
        // double lt;
        // double lg;

        //lists = Db_helper.Readlats(lists.Id);

        //lt = lists.latitude;

        //lg = lists.longtitude;
        return new GeoCoordinate
            (
            Findcar.lt,
            Findcar.lg,
            geocoordinate.Altitude ?? Double.NaN,
            geocoordinate.Accuracy,
            geocoordinate.AltitudeAccuracy ?? Double.NaN,
            geocoordinate.Speed ?? Double.NaN,
            geocoordinate.Heading ?? Double.NaN
            );
    }
}

and hers is the xaml code so that you can see the problem clearly

<phone:PhoneApplicationPage
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"
xmlns:shell="clr-namespace:Microsoft.Phone.Shell;assembly=Microsoft.Phone"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:maps="clr-namespace:Microsoft.Phone.Maps.Controls;assembly=Microsoft.Phone.Maps" xmlns:Toolkit="clr-namespace:Microsoft.Phone.Maps.Toolkit;assembly=Microsoft.Phone.Controls.Toolkit"
 xmlns:Location="clr-namespace:System.Device.Location;assembly=System.Device"
xmlns:maptk="clr-namespace:Microsoft.Phone.Maps.Toolkit;assembly=Microsoft.Phone.Controls.Toolkit"

x:Class="SmartParking.Findcar"
FontFamily="{StaticResource PhoneFontFamilyNormal}"
FontSize="{StaticResource PhoneFontSizeNormal}"
Foreground="{StaticResource PhoneForegroundBrush}"
SupportedOrientations="Portrait" Orientation="Portrait"
mc:Ignorable="d"
shell:SystemTray.IsVisible="True">

<!--LayoutRoot is the root grid where all page content is placed-->
<Grid x:Name="LayoutRoot" Background="Transparent">
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="*"/>
    </Grid.RowDefinitions>

    <!--TitlePanel contains the name of the application and page title-->
    <StackPanel Grid.Row="0" Margin="12,17,0,28">
        <TextBlock Text="Smart Parking" Style="{StaticResource PhoneTextNormalStyle}"/>
        <TextBlock Text="Find my car" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>
    </StackPanel>

    <!--ContentPanel - place additional content here-->
    <Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
        <StackPanel>
            <!--<TextBlock TextWrapping="Wrap" FontSize="40" Text="Wher is my car" FontWeight="Bold" Foreground="Red"/>
            --><!--<TextBlock x:Name="Floor_fc" TextWrapping="Wrap" Text="Floor : " FontSize="29.333"/>
            <TextBlock x:Name="Zone_fc" TextWrapping="Wrap" Text="Zone :" FontSize="29.333"/>--><!--
            <TextBlock TextWrapping="Wrap" Text="Check on the maps"  FontSize="29.333"/>-->
            <!--<maps:Map Height="232" Tap="Map_Tap" PedestrianFeaturesEnabled="True" LandmarksEnabled="True" ColorMode="Dark"/>-->
            <maps:Map Height="519" Grid.Row="1" x:Name="mymap" Margin="0" ZoomLevel="16">
                <maptk:MapExtensions.Children>


                </maptk:MapExtensions.Children>
            </maps:Map>
            <Button Tap="TextBlock_Tap">Direction to my car</Button>
        </StackPanel>

    </Grid>
</Grid>

Answer 1

When you zoom out the map size goes smaller on screen and pushpin's (your point position icon/image) size is as it is. So visibly you will find that location point is changing its location.

But again when you zoom in, it will be on the exact place where it should be.

PS:If location point size also gets decreased while zoom out, at one time user may not see it properly.

Answer 2

So if you want to set a Pushpin on the map and want it to always shows your current location, you can try this:

Here the C# code:

GeoCoordinate myPosition = null;
UserLocationMarker marker = (UserLocationMarker)this.FindName("UserLocationMarker");
marker.GeoCoordinate = myPosition;

Here the XAML code:

<toolkit:UserLocationMarker x:Name="UserLocationMarker" Visibility="Collapsed">
                <toolkit:UserLocationMarker.Template>
                    <ControlTemplate TargetType="toolkit:UserLocationMarker">
                        <StackPanel>
                            <Border x:Name="pinBorder" Background="Black" Width="30" Height="30" CornerRadius="30" HorizontalAlignment="Center" VerticalAlignment="Center">
                                <Ellipse x:Name="pinEllipse" Fill="#FF00A300" Stroke="White" StrokeThickness="2" Width="24" Height="24" HorizontalAlignment="Center" VerticalAlignment="Center"/>
                            </Border>
                        </StackPanel>
                    </ControlTemplate>
</toolkit:UserLocationMarker.Template>