[OpenLayers-Users] Is it possible to edit a LineString after it has been created and added to a layer?

[Curtis Olson]

Hi Michael (and everyone else who replied),

Thanks for your quick replies.  I'm working on this some more today and
have some follow up questions.

I define my point list in the global scope:

var route_points = new Array();

Then I populate this array with a few points.

Finally I can build the structures and add the result to a layer so I can
see it (and I do see the result.)

lineString = new OpenLayers.Geometry.LineString(route_points);
route_vector = new OpenLayers.Feature.Vector(lineString,null,home_style);
routeLayer.addFeatures( route_vector );

Later I go back and change the location of a point in my route_list array
of points.

route_points[2].lon = newlon;
route_points[2].lat = newlat;

But nothing changes on screen.  (for what it's worth, I can recreate all
these structures and add them as a new layer to my map and I do see the new
points in their correct locations, but it's as a new feature along with the
old -- I'm hoping to be able to simply modify the old structure rather than
having to create a new (potentially large/complex) structure each iteration.

I am wondering if the lineString or the Vector constructors use a copy of
the upstream structure rather than a pointer to the structure? In that case
changing my original structure would have no effect.

I wouldn't mind using accessor functions to find the actual data point, but
as I look through the class definitions and inheritance, I don't see any
way to get back to the original point array when starting from a Vector()
or a LineString()?

I'm probably missing something stupid or easy, but I'm just not seeing it?
 Am I on the right track or missing by a mile?

Thanks,

Curt.



On Wed, Apr 11, 2012 at 2:22 PM, Michael <mdm at yachtpc.com> wrote:

>  Both are doable.  You need to do a little digging to be sure you are
> pointing to the correct point when you either change its lonlat or delete
> it.  Then you need to redraw the line.
>
> In my application, I maintained a separate array pointing to the points in
> my line.  Possibly not the most efficient, but it worked.
>
> Michael
>
>
> On 4/11/2012 12:08 PM, Curtis Olson wrote:
>
> Hi,
>
>  I've begun my plunge into openlayers and have a number of things working,
> but I've run into a question that I haven't been able to answer for myself
> from the docs and the mailing list archives.
>
>  I am building a map that will live track an object (for example: my
> aircraft location as I fly in the FlightGear flight simulator.)
>
>  I would like to leave a trail behind myself showing my recent path (say
> for the past 10 seconds or the past 10 minutes.)  I am imagining a
> LineString where I can insert new points at one end and remove points from
> the other end -- as my position updates.
>
> I could create an entirely new LineString and Vector and add that to my
> layer 10x a second (removing the old feature), but I was hoping I could
> just build the linestring once, add it too a layer once, and from then on
> just modify the linestring structure.
>
> Is something like this possible or am I barking up the wrong tree?
>
>  I have another sort of similar situation where I may want to
> additionally modify the point locations of some of the points in the
> linestring (based on external data coming from the flight simulator.)  In
> otherwords I want to reshape the linestring by adjusting the locations of
> individual points.  Is anything like this possible?
>
> I've been hunting through the examples and the documentation and haven't
> stumbled on the appropriate magic yet.
>
>  Any tips or pointers or nudges for an openlayers newbie?
>
> Thanks,
>
>  Curt.
> --
>  Curtis Olson:
> http://www.atiak.com - http://aem.umn.edu/~uav/
> http://www.flightgear.org - http://gallinazo.flightgear.org
>
>
>
> _______________________________________________
> Users mailing listUsers at lists.osgeo.orghttp://lists.osgeo.org/mailman/listinfo/openlayers-users
>
>
> _______________________________________________
> Users mailing list
> Users at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/openlayers-users
>
>


-- 
Curtis Olson:
http://www.atiak.com - http://aem.umn.edu/~uav/
http://www.flightgear.org - http://gallinazo.flightgear.org
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.osgeo.org/pipermail/openlayers-users/attachments/20120412/264b9e5a/attachment.html