topic Re: Image doesn't display when it's position and the Extent of the Map changed. in ArcGIS API for Silverlight Questions

Image doesn't display when it's position and the Extent of the Map changed.

hunterruan — Thu, 27 May 2010 06:51:58 GMT

Please see the following code:

xaml code:

 <esri:ArcGISTiledMapServiceLayer ID="MyLayer" 
                Url="http://server.arcgisonline.com/ArcGIS/rest/services/ESRI_StreetMap_World_2D/MapServer" />

            <esri:ElementLayer ID="MyElements">
                <esri:ElementLayer.Children>
                    <Button x:Name="RedlandsButton" Width="100" Height="20" Content="ShowImage"  
            esri:ElementLayer.Envelope="-10,10,-10,10" Click="RedlandsButton_Click"
            VerticalAlignment="Center" HorizontalAlignment="Center" ToolTipService.ToolTip="help"
            >
                    </Button>
                    <Image x:Name="Pic" Source="../pin_red.png" Stretch="None" 
                           esri:ElementLayer.Envelope="0,0,0,0" VerticalAlignment="Top" HorizontalAlignment="Left"></Image>


                    <Image x:Name="HoldPic" Source="../pin_red.png" Stretch="Fill" Visibility="Collapsed" 
                           esri:ElementLayer.Envelope="0,0,0,0" VerticalAlignment="Top" HorizontalAlignment="Left"></Image>


                </esri:ElementLayer.Children>
            </esri:ElementLayer>
        </esri:Map>

cs code:

public ElementVisibilityWithMapExtent()
        {
            InitializeComponent();
            LocalMap.Extent = new Envelope(-20,-20,20,20); 
        }

        private void RedlandsButton_Click(object sender, RoutedEventArgs e)
        { 
            Image image = (LocalMap.Layers["MyElements"] as ElementLayer).Children[1] as Image;
            image.Visibility = Visibility.Visible;
            ElementLayer.SetEnvelope(image,new Envelope(-30,30,-30,30));

            //This extent is availble for the map to show the image
            //LocalMap.ZoomTo(new Envelope(-103.0947, -41.07186, 58.95613, 68.22523));

            LocalMap.ZoomTo(new Envelope(-103.0947, 21.07186, 58.95613, 68.22523));
        }

After clicking the Button, the extent of the map is changed but the Image doesn't display on the map.

How can I show the Image successfully?

Re: Image doesn't display when it's position and the Extent of the Map changed.

dotMorten_esri — Thu, 27 May 2010 15:25:52 GMT

This line : esri:ElementLayer.Envelope="0,0,0,0" means "show the image at equator/greenwich with the size of the image (which you never set width/height on - you should)". When you change it to -30,30,-30,30, this means its still centered on equator/greenwich, but now 60map units wide and high (width/height of image will be overridden. However you are zooming to -103.0947, 21.07186, 58.95613, 68.22523, which doesn't intersect -30,30,-30,30.

Other things to check: Is your image path correct?

Re: Image doesn't display when it's position and the Extent of the Map changed.

hunterruan — Fri, 28 May 2010 00:53:09 GMT

Thanks for your reply.

The image path is correct and I can see the image if I zoom map to the full extent by mouse before clicking button, this is confusing me also.

I have another idea on the Envelop (-30,30,-30,30) for the Image, I regard it as the position (-30,30) for the Image and it looks like this.

It's easy to test it , could you help me to figure out it?

Re: Image doesn't display when it's position and the Extent of the Map changed.

dotMorten_esri — Fri, 28 May 2010 16:45:00 GMT

Before you go down this road, I'm wondering why you are not using a GraphicsLayer ? There's nothing in this post (or your other one) that makes use of something the GraphicsLayer couldn't very easily do.

Re: Image doesn't display when it's position and the Extent of the Map changed.

hunterruan — Mon, 31 May 2010 06:18:54 GMT

Thanks for your suggestion. But I really want to use the ElementLayer and have some Images on the map.
I had tired the GraphicLayer but I didn't find the way to set VerticalAlignment and HorizontalAlignment on the Image symbol and it's not easy to add the Maptips on the Image, I know the way to set the maptips but it is not convenient on my page for some reason.

Thanks anyway. Hope some guy have other good idea.