[OpenLayers-Users] Accessing the events of DrawFeature and ModifyFeature to calculate area

[Albert Ang]

Hi Christoph,

thank you very much for your assistance. I tried the following and it works
beautifully. One little problem is the closing of the polygon vertices.
Before adding the events listeners, a simple double-click will close the
polygon. After adding the events, sometimes I need to double-click twice to
close the polygon. Not a big problem though. Thanks again. - Albert Ang

function report(event) {
                //OpenLayers.Console.log(event.type, event.feature ?
event.feature.id : event.components);
    displayWKT(event.feature);
 }

aoi.events.on({
                "beforefeaturemodified": report,
                "featuremodified": report,
                "afterfeaturemodified": report,
                "vertexmodified": report,
                "sketchmodified": report,
                "sketchstarted": report,
                "sketchcomplete": report
});

function displayWKT(feature) {
            var str = wkt.write(feature);
            // not a good idea in general, just for this demo
            //str = str.replace(/,/g, ', ');
            document.getElementById('info').innerHTML = str;
   document.aoi.vertex.value = str;

   var areaAOI = feature.geometry.getGeodesicArea();
   areaAOI = areaAOI / 1000000;
   var areaAOIstr = 'Approx. area : ' + areaAOI + ' sq. km';
   document.getElementById('area').innerHTML = areaAOIstr;
        } // end function displayWKT(feature)

On Fri, Feb 19, 2010 at 2:05 AM, Christoph Ratke <christoph.ratke at gmx.net>wrote:

> Hi Mr. Ang,
>
> you can have a look here:
>
> http://dev.openlayers.org/releases/OpenLayers-2.8/examples/modify-feature.html
> or here:
>
> http://dev.openlayers.org/releases/OpenLayers-2.8/examples/highlight-feature.html
>
> Have a good day,
> Christoph
>
>
> Albert Ang schrieb:
>  > Dear all,
> >
> > I need assistance in using the events of DrawFeature and
> > ModifyFeature. Can anyone provide some examples? I use the DrawFeature
> > and ModifyFeature as following but need guidance on how to use the
> > events of DrawFeature (featureadded) and ModifyFeatures
> > (featuremodified). Basically I like to use the
> > feature.geometry.getGeodesicArea() function to calculate area
> > dynamically when an user draws a polygon or when he modifies the polygon.
> >
> > controls = {
> >                 dpolygon: new OpenLayers.Control.DrawFeature(aoi,
> >                             OpenLayers.Handler.Polygon, drawOptions),
> >                 modify: new OpenLayers.Control.ModifyFeature(aoi,
> >
> > modifyOptions),
> >               selectVector: new OpenLayers.Control.SelectFeature(aoi,
> > wktOptions)
> > }
> >
> > Thank you in advance.
> >
> > Albert
> > ------------------------------------------------------------------------
> >
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> >
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