[OpenLayers-Users] populate vector layer from json response
B. Heath Robinson
heath at midnighthour.org
Tue Jun 21 11:44:02 EDT 2011
I should have proofread the email BEFORE I sent it.
Actually, it would be something like this:
var latlon = new OpenLayers.LonLat(tweet.geo.coordinates[0],tweet.geo.coordinates[1]);
latlon.transform(new OpenLayers.Projection("EPSG:4326"),map.getProjectionObject());
tweet.point = latlon;
This assumes that tweet.geo.coordinates[0],tweet.geo.coordinates[1] is something that the LonLat constructor will take.
On Jun 21, 2011, at 10:39 AM, B. Heath Robinson wrote:
> Transform operates on the coordinates, it does not return a new coordinates. You should use it like this:
> var latlon = weet.geo.coordinates[0],tweet.geo.coordinates[1];
> latlon.transform(new OpenLayers.Projection("EPSG:4326"),map.getProjectionObject());
> tweet.point = latlon;
>
>
> On Jun 21, 2011, at 10:21 AM, Nicholas Efremov-Kendall wrote:
>
>> Hi guys thanks for the previous advice,
>>
>> I'm still running into an issue, and I'm not sure how to resolve it. When I first use a OpenLayers.LonLat and transform the point, I get the lon converted correctect, but the lat is returned NaN. If I don't transform it, the coordinates remain correct.
>>
>> tweet.point = new OpenLayers.LonLat(tweet.geo.coordinates[0],tweet.geo.coordinates[1]).transform(new OpenLayers.Projection("EPSG:4326"),map.getProjectionObject());
>>
>> I've been playing around with some different iterations, and I can get tweet.point to alert out with ever tweet that's pulled into the plotting function, but the markers aren't added. The issue seems to be with how I'm calling the transform function, because somehow after calling the function I get NaN's for the lat-lon's inside the point object. I'm really hitting a wall here.
>>
>>
>>
>> On Tue, Jun 21, 2011 at 3:23 AM, Nick Kendall <n.e.kendall at gmail.com> wrote:
>> Thanks! Will take another crack at this Tom!
>>
>> Sent from my mobile device
>>
>> On Jun 21, 2011, at 2:37 AM, "Sveen Atle Frenvik (Geomatikk IKT)" <Atle.Frenvik.Sveen at geomatikk.no> wrote:
>>
>>> try using an OpenLayers.Geometry.Point instead of an OpenLayers.LonLat
>>>
>>> ie (untested, but i think this is rather correct):
>>>
>>> function parseTweetsQ(){
>>> if (tweetsQ.length > 0) {
>>> var tweet = tweetsQ.pop();
>>> if (tweet.geo){
>>> tweet.point = new OpenLayers.Geometry.Point(tweet.geo.coordinates[0],tweet.geo.coordinates[1]).transform(new OpenLayers.Projection("EPSG:4326"),map.getProjectionObject());
>>> tweet.attributes = {}; //in this you coukd stuff attributes of the tweet for easy access on clicks etc.
>>> plotTwt(tweet);
>>> }
>>> }
>>> }
>>>
>>> function plotTwt(tweet){
>>> //why do you keep adding the layer for each tweet?
>>> map.addLayer(tweetz);
>>> tweet.marker = new OpenLayers.Feature.Vector(tweet.point,{attributes:{tweet.attributes]});
>>> tweetz.addFeatures([tweet.marker]);
>>> }
>>>
>>>
>>>
>>> On 2011-06-21 05:00, Nicholas Efremov-Kendall wrote:
>>>>
>>>> Hi Phil et al,
>>>>
>>>> Thanks for your response. The code as is does iterate through the features as they are returned. I have a handle on it up to the plotting function. An alert on the tweet.marker object returns [object Object], while tweet.latlng returns readable coordinates lon=38.6834,lat=-90.4313. I guess what I'm unsure about is how to parse the object which is passed to the third function. Thanks again.
>>>>
>>>>
>>>> function acquireTweets(){
>>>> $.getJSON(createTWTsrcURL(), function(data){
>>>> if(data.results)
>>>> $.each(data.results, function(i, tweet){
>>>> if (tweet.geo || tweet.location)
>>>> tweetsQ.push(tweet);
>>>> });
>>>> refreshQuery = data.refresh_url;
>>>> });}
>>>>
>>>> function parseTweetsQ(){
>>>> if (tweetsQ.length > 0) {
>>>> var tweet = tweetsQ.pop();
>>>> if (tweet.geo){
>>>> tweet.latlng = new OpenLayers.LonLat(tweet.geo.coordinates[0],tweet.geo.coordinates[1]);
>>>> plotTwt(tweet);
>>>> }}}
>>>>
>>>> function plotTwt(tweet){
>>>> map.addLayer(tweetz);
>>>> tweet.marker = new OpenLayers.Feature.Vector(new OpenLayers.Geometry.Point(tweet.latlng).transform(new OpenLayers.Projection("EPSG:4326"),map.getProjectionObject()));
>>>> tweetz.addFeatures([tweet.marker]);}
>>>>
>>>>
>>>>
>>>>
>>>> On Mon, Jun 20, 2011 at 9:13 PM, Phil Scadden <p.scadden at gns.cri.nz> wrote:
>>>> I have no idea what the object returned by twitter is but surely, but if
>>>> you are using jsonp, then
>>>> have in your code something like:
>>>> jsonp_function(json)
>>>> where jsonp_function is the name of jsonp callback and json is the
>>>> returned object. I would guess it contains an array of feature type
>>>> objects, so you would iterate through the array, creating feature for
>>>> each row, and calling vectorLayer.addFeatures(features) to add them to
>>>> the vector layer.
>>>>
>>>> Notice: This email and any attachments are confidential. If received in error please destroy and immediately notify us. Do not copy or disclose the contents.
>>>>
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>>>
>>>
>>> --
>>> Atle Frenvik Sveen
>>> Utvikler
>>> Geomatikk IKT AS
>>> tlf: 45 27 86 89
>>> atle.frenvik.sveen at geomatikk.no
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>>
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