Problem with Rotation of a MarkerSymbol

AaronBishop — Thu, 11 Aug 2011 14:47:32 GMT

Hi,

We are working on an Esri silverlight application (latest versions) -- and are having a problem with how the rotation of a MarkerSymbol works. Basically, the application is a fleet tracking system, where each vehicle has its coordinates reported in real time, along with the direction the vehicle is facing.

We have a GraphicsLayer that contains all of the vehicle symbols, and the symbol has its rotation set using something like...

<Image RenderTransformOrigin="0.5,0.5" Source="{Binding Attributes[ImageLoc]}">
    <Image.RenderTransform>
        <RotateTransform Angle="{Binding Attributes[Heading]}"/>
    </Image.RenderTransform>
</Image>

and...

graphic.Attributes["Heading"] = heading;

That works well, and the units are displayed on the map correctly. However, when the application tries to adjust the positions of the vehicles (which happens every second, let's say) -- it does so by creating a new GraphicsLayer, and filling it with a symbol for each vehicle. The old layer is then removed and the new layer takes its place.

Again -- that works well, except there is a 1 frame flicker -- where all vehicles are drawn pointing Northwards instead of their correct orientation. Does anyone have any advice on how to get this working without that flicker?

Thanks,
-Aaron

PS -- we have tried this several other ways... Having a single layer and adjusting the heading of existing markers does not flicker -- however it takes a long time (1 second or so) -- guessing because it redraws after each marker is updated or something along those lines.

Re: Problem with Rotation of a MarkerSymbol

DominiqueBroux — Tue, 30 Aug 2011 07:37:43 GMT

The rotatetransform angle binding kicks in after the symbol has been first displayed (so without any rotation). Then the binding kicks in and the symbol is rotated --> flicking effect.

One possible workaround is to use a surrogate binder attached property instead of a transform binding.
You will find a sample with the kmllayer of the ArcGIS WinPhone toolkit (since WinPhone doesn't support transform bindings).

I attached the 2 interesting files.

topic Problem with Rotation of a MarkerSymbol in ArcGIS API for Silverlight Questions

Problem with Rotation of a MarkerSymbol

Re: Problem with Rotation of a MarkerSymbol