[OpenLayers-Users] Is it possible to edit a LineString after
it has been created and added to a layer?
Michael
mdm at yachtpc.com
Thu Apr 12 16:49:03 EDT 2012
Ah yes, the use of alerts. Good work!
On 4/12/2012 1:34 PM, Curtis Olson wrote:
> Hi all,
>
> I think I have figured this out -- after some tedious back and forth
> through the documentation and dumping out intermediate structures with
> "alert".
>
> If I start with this:
>
> var route_points = new Array();
> var multipoint = new OpenLayers.Geometry.MultiPoint(route_points);
> var route = new OpenLayers.Feature.Vector(multipoint);
> myLayer.addFeatures( route );
>
> Then later I can get the point list by accessing:
>
> var pts = route.geometry.components;
>
> Then I can modify a point by:
>
> pts[3].lon = newlon;
> pts[3].lat = newlat;
>
> And then I need to call myLayer.redraw() to see the change. I can add
> or remove points to this list as well. Seems to do the trick!
>
> Thanks,
>
> Curt.
>
>
> On Thu, Apr 12, 2012 at 12:01 PM, Michael <mdm at yachtpc.com
> <mailto:mdm at yachtpc.com>> wrote:
>
> Hi Curt
>
> Yes, as I recall (and I will dig into my code as soon as I pay
> bills) a copy is constructed. So you need to walk through the
> points in the line itself and find the one that matches the one
> you want to change (I gave them all ids). THEN change it, THEN
> redraw the line. If you are doing a lot of lines or points, do
> them all then redraw the layer.
>
> Michael
>
>
> On 4/12/2012 9:36 AM, Curtis Olson wrote:
>> 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
>> <mailto: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://aem.umn.edu/%7Euav/>
>>> http://www.flightgear.org - http://gallinazo.flightgear.org
>>>
>>>
>>>
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>>
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>>
>>
>> --
>> Curtis Olson:
>> http://www.atiak.com - http://aem.umn.edu/~uav/
>> <http://aem.umn.edu/%7Euav/>
>> http://www.flightgear.org - http://gallinazo.flightgear.org
>>
>>
>>
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>
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>
>
> --
> Curtis Olson:
> http://www.atiak.com - http://aem.umn.edu/~uav/
> <http://aem.umn.edu/%7Euav/>
> http://www.flightgear.org - http://gallinazo.flightgear.org
>
>
>
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> http://lists.osgeo.org/mailman/listinfo/openlayers-users
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