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Labels on a RadMap

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James
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James asked on 08 Aug 2014, 06:17 PM
Hi,
  I am using a RadMap that depicts a number of physical area around the map that are drawn with MapPolygons.  This works great.  I am trying to put text inside each corner of each MapPolygon to tell users what area they are viewing.  I need the scale of this text to match the map's scale as the user zooms in and out.  I have added labels with a number of approaches, but I always find that they don't scale correctly  when you zoom in.  For example, in the attached file you will see how the text gets very small as you zoom in.  In that file you will also see the way I need the text to look.

 In this example the following code gets executed for each corner in a given MapPolygon that I am trying to label:

                Grid grid = new Grid();
                grid.Background = new SolidColorBrush(Colors.White);
                TextBlock text = new TextBlock();
                text.Foreground = new SolidColorBrush(Colors.Purple);
                text.Text = "My Label Data";
                grid.Children.Add(text);

                Location newLocation = ... (based on MapPolygon corner)
                MapLayer.SetLocation(grid, newLocation);
                this.informationLayer.Items.Add(grid);

  Is there a way to add text to a RadMap and have it keep its location and scale correctly as a user zooms in/out?

Thanks.

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Andrey
Telerik team
answered on 12 Aug 2014, 06:08 AM
Hello James,

You can use the BaseZoomLevel, MinScale and MaxScale attachable properties of MapLayer to make the FrameworkElement scalable. For more information I would recommend you to take a look at the following documentation topic:
http://www.telerik.com/help/silverlight/radmap-features-information-layer-framework-elements.html

Also I would recommend you to use the Hot Spot feature.

Regards,
Andrey Murzov
Telerik
 
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Ludmila
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answered on 26 Aug 2014, 06:13 AM
Hi James,

May be I’m a bit late but here it is an example of how we do it in our projects. We use VisualizationLayer instead of Information layer so my sample is based on it (I suppose that you can use the same approach with InformationLayer):

<telerik:RadMap x:Name="radMap"
                ZoomLevel="7"
                Center="44.6957539183824, 25.3327663758679">
    <telerik:RadMap.Provider>
        <telerik:OpenStreetMapProvider />
    </telerik:RadMap.Provider>
    <telerik:VisualizationLayer x:Name="polygons" />
    <telerik:VisualizationLayer x:Name="labels" />
</telerik:RadMap>

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
 
        PolylineData polyline = new PolylineData()
        {
            ShapeFill = new MapShapeFill()
            {
                Stroke = new SolidColorBrush(Colors.Red),
                StrokeThickness = 2
            }
        };
 
        LocationCollection points = new LocationCollection();
        points.Add(new Location(44.6957539183824, 23.3327663758679));
        points.Add(new Location(44.1429369264591, 24.7498095849434));
        points.Add(new Location(44.5131732087098, 27.4611884843576));
        points.Add(new Location(45.2073941930888, 27.9275176988258));
 
        polyline.Points = points;
 
        this.polygons.Items.Add(polyline);
 
        this.AddLabels(points);
    }
 
    private void AddLabels(LocationCollection points)
    {
        foreach (Location point in points)
        {
            Grid grid = new Grid();
            grid.Background = new SolidColorBrush(Colors.White);
            TextBlock text = new TextBlock();
            text.Foreground = new SolidColorBrush(Colors.Purple);
            text.Text = "My Label Data";
            grid.Children.Add(text);
 
            Location newLocation = point;
            MapLayer.SetLocation(grid, newLocation);
            MapLayer.SetBaseZoomLevel(grid, 7);
            this.labels.Items.Add(grid);
        }
    }
}


Pay attention, I’m using MapLayer.SetBaseZoomLevel attachable property to make labels resizable when zooming.

Best Regards
Ludmila Murzova
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James
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answered on 27 Aug 2014, 01:25 PM
Hi Ludmila,
  Thank you very much.  This is really helpful.

James
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