[OpenLayers-Users] Zoom on GML extent

Tue Jan 19 18:06:26 EST 2010

2010/1/18 christophe triquet <nethou at aliceadsl.fr>

>
> 2010/1/18 Christopher Schmidt <crschmidt at metacarta.com>
>
> On Mon, Jan 18, 2010 at 01:32:24PM +0100, christophe triquet wrote:
>> > Hi,
>> >
>> > I'm adding a GML file in my map with the object OpenLayers.Layer.GML.
>> I'm
>> > trying to zoom to this layer extent at map's loading. I can do this if I
>> > know de bounding box coordinates with a postgis query.
>> >
>> > My PHP code :
>> >
>> >         var bounds = new OpenLayers.Bounds();
>> >         bounds.extend((new
>> > OpenLayers.LonLat(<?=$xmin?>,<?=$ymin?>)).transform(wgs84,
>> > map.getProjectionObject()));
>> >         bounds.extend((new
>> > OpenLayers.LonLat(<?=$xmax?>,<?=$ymax?>)).transform(wgs84,
>> > map.getProjectionObject()));
>> >         bounds.toBBOX();
>> >         map.zoomToExtent(bounds);
>> >
>> > But this requires a server call and I want my map to use only datas in
>> the
>> > GML file and not to have to connect to a database.
>> >
>> > I have seen that GML files includes bounded box informations like :
>> >
>> >   <gml:boundedBy>
>> >     <gml:Box>
>> >
>> >
>> <gml:coord><gml:X>1.473839004763629</gml:X><gml:Y>43.43941299999661</gml:Y></gml:coord>
>> >
>> >
>> <gml:coord><gml:X>1.647671004707115</gml:X><gml:Y>43.58098800002078</gml:Y></gml:coord>
>> >     </gml:Box>
>> >   </gml:boundedBy>
>> >
>> > Is it possible the get the gml extent to be able to automaticaly zoom on
>> it
>> > at loading ?
>>
>> Formats have a 'keepData' option or something like that, which then
>> stashes
>> the data on the .data property of the format. You could then use standard
>> DOM methods to parse the data.
>>
>> Alternatively, you could just do:
>>
>>  map.zoomToExtent(dataLayer.getDataExtent());
>>
>> after the loadend event fires on the layer, which would iterate over the
>> features and get a bounding box.
>>
>> Regards,
>> --
>> Christopher Schmidt
>> MetaCarta
>>
>
> Thank you everybody for your answears.
>
> That :
>
> var vectorLayer = ...;
> vectorLayer.events.on({
>   "loadend": function() {
>       map.zoomToExtent(vectorLayer.
> getDataExtent());
>   }
> });
> works if I deactivate and then reactivate my layer.
>
> What I'm trying to do is to zoom to the extent at loading time.
>
> The map.zoomToExtent(dataLayer.getDataExtent()); gives me a javascript
> error "Bounds is null".
>
> Maybe, I'm not calling this at the right time ? I have added this
> if (!map.getCenter()) map.zoomToExtent(dataLayer.getDataExtent());
> at the end of typical init method called in <body onload="init()">.
>
> Any idea of what I'm doing wrong ?
>
> Regards,
> Christophe
>

I think now my question is about events management.

If I put in my init function something like

        dataLayer.events.on({
            "loadend": function() {
                map.zoomToExtent(dataLayer.getDataExtent());
            }
        });

I get the zoom on layer extend (what I want) if I uncheck and then check the
layer in the layer switcher.

Is there any way to trigger that event when the map loads ?

Thanks for your answears,
Christophe
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