[ka-Map-users] Function to clear addObjectGeo

[Stephen Woodbridge]

Chris,

I'm not sure how to do this or if it is possible, but it would seem like 
you would want to have each marker destroy itself if you panned outside 
the extended extent or changed zoom scale. Otherwise you will have a 
object leak and continue to create these markers as long as the user has 
the page open.

One way to do it might be to make a structure the contains all the 
objects that your create and a variable the describes the valid context 
that were created for. Then before you add new markers for an context 
that does not match the save context, you can destroy all the old 
markers before adding the new markers.

Just an idea.
   -Steve W.

Base Bloc wrote:
> Hi Guys,
> 
>  
> 
> I’m still plugging away to get some workable functions together to draw 
> markers with tool-tips and it’s hard work as I’m experienced with PHP 
> but not so hot on JavaScript and DOM so am making all the usual mistakes 
> but getting there slowly. I now have a system in place that at a curtain 
> scale places markers within an extended extent of the visible map tiles 
> using HttpRequest. All is working fine and I currently have the system 
> getting markers from a database to place markers on the map at the 
> required scale (1:300000), then adding more markers as the map is panned.
> 
>  
> 
> The problem I’m encountering now is that although the function is 
> working correctly as in it won’t add markers+tool-tips until the map is 
> zoomed to 1:300000 when the map is zoomed back out above 1:300000 the 
> markers previously called all remain on screen and as there are over 
> 7000 points you can imagine what this looks like at 1:4000000.
> 
>  
> 
> Is there a simple way to clear all of the markers created by 
> addObjectGeo when the map is zoomed out past a curtain scale or better 
> yet add an event related to myKaMap.getCurrentScale() so they are only 
> displayed when the scale in greater than X?
> 
>  
> 
> Here are the functions I’m using at present:
> 
>  
> 
> //creates separate image for each marker
> 
> function create_marker (img_id, var_1, lat, lon)
> 
>             {
> 
>            
> 
>     document[img_id] = document.createElement( 'img' );
> 
>     document[img_id].src = 'images/kamap.gif';
> 
>            
> 
>                         var bname = navigator.appName;
> 
>                         if (bname == "Microsoft Internet Explorer")
> 
>                {
> 
>                         document[img_id].attachEvent("onmouseover",tool_tip)
> 
>                         
> document[img_id].attachEvent("onmouseout",tool_tip_out)
> 
>                         document[img_id].attachEvent("onclick",page_link)
> 
>                }
> 
>                         else
> 
>                {
> 
>                         
> document[img_id].addEventListener("mouseover",tool_tip,false)
> 
>                         
> document[img_id].addEventListener("mouseout",tool_tip_out,false)
> 
>                         
> document[img_id].addEventListener("click",page_link,false)
> 
>                }
> 
>               
> 
>                                     //Sends content and format options 
> to tool-tip      
> 
>                                     function tool_tip(){
> 
>            
> 
>                                                 var test_var = var_1;
> 
>                                                 var text = "My name is " 
> +test_var+ ", and I'm am now understanding JavaScripts";
> 
>                                                 overlib(text, STICKY, 
> MOUSEOFF, CAPTION, 'info')
> 
>                                                 }
> 
>  
> 
>     myKaMap.addObjectGeo( myCanvas, lat, lon, document[img_id] );
> 
>            
> 
>             }
> 
>            
> 
>             function drawMarkers(){
> 
>   Big_Extents = myKaMap.getGeoExpandedExtents();
> 
>   myCanvas = myKaMap.createDrawingCanvas( 5000 );
> 
>   
> 
>   //draw Markers within Big_Extents using kaXMLOverlay or just 
> addObjectGeo()
> 
>  
> 
>             var scale = myKaMap.getCurrentScale();
> 
>            
> 
>             if (scale <= 200000)
> 
>             {
> 
>            
> 
>             //this is where the HttpRequest would normally go, but I 
> have placed a couple of sample markers to make the script more clear
> 
>             create_marker('C02573', 'Box', 511275, 1363860);
> 
>             create_marker('C02574', 'Pipe', 515736, 1364260);
> 
>  
> 
>             }
> 
>  
> 
> }
> 
>            
> 
> var scale = myKaMap.getCurrentScale();
> 
>  
> 
>            
> 
>             myKaMap.registerForEvent( KAMAP_SCALE_CHANGED, null, 
> drawMarkers );
> 
>             myKaMap.registerForEvent( KAMAP_EXTENTS_CHANGED, null, 
> maybeRedraw );
> 
>             myKaMap.registerForEvent( KAMAP_MAP_INITIALIZED, null, 
> drawMarkers );
> 
>  
> 
> }
> 
>  
> 
> Sorry there are a few calls to functions there which I have not added 
> above, I didn’t want to do a 500 line cut and paste, once I have it 
> working properly I will post the full code and related functions.
> 
>  
> 
> Any suggestions on a fix to this problem would be appreciated.
> 
>  
> 
> Thanks,
> 
>  
> 
> Chris
> 
>  
> 
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Christopher Brown
> 
> Head of Internet Development
> 
> Base Bloc Cambodia
> 
> #33, 123, Phnom Penh, Cambodia.
> 
> P.O. Box 2086
> 
> www.basebloc.com
> 
> Tel (+885) 12 315 302
> 
>  
> 
> 
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