KML layer in Openlayers doesn't work on localh

2019-02-10 17:24发布

站内文章 / JavaScript
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问题:

I have strange problem with rendering KML file in OpenLayers. It seems to be easy, but it's not. I've started with an example from here OpenLayers example . I wanted to add my own KML. It didn't work. I've created a local copy of the example with absolute urls, as follows:

<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0">
    <meta name="apple-mobile-web-app-capable" content="yes">
    <link rel="stylesheet" href="http://openlayers.org/dev/theme/default/style.css" type="text/css" />
    <link rel="stylesheet" href="http://openlayers.org/dev/examples/style.css" type="text/css" />
    <script src="http://openlayers.org/dev/OpenLayers.js"></script>            
    <style type="text/css">
        html, body {
            height: 100%;
        }
        #map {
            width: 100%;
            height: 80%;
            border: 1px solid black;
        }
        .olPopup p { margin:0px; font-size: .9em;}
        .olPopup h2 { font-size:1.2em; }
    </style>
    <script type="text/javascript">


        var lon = 5;
        var lat = 40;
        var zoom = 5;
        var map, select;

        function init(){
            map = new OpenLayers.Map('map');

            var wms = new OpenLayers.Layer.WMS(
                "OpenLayers WMS",
                "http://vmap0.tiles.osgeo.org/wms/vmap0",
                {layers: 'basic'}
            );

            var sundials = new OpenLayers.Layer.Vector("KML", {
                projection: map.displayProjection,
                strategies: [new OpenLayers.Strategy.Fixed()],
                protocol: new OpenLayers.Protocol.HTTP({
                    url: "http://openlayers.org/dev/examples/kml/sundials.kml",
                    format: new OpenLayers.Format.KML({
                        extractStyles: true,
                        extractAttributes: true
                    })
                })
            });

            map.addLayers([wms, sundials]);
            alert("deded");
            select = new OpenLayers.Control.SelectFeature(sundials);

            sundials.events.on({
                "featureselected": onFeatureSelect,
                "featureunselected": onFeatureUnselect
            });

            map.addControl(select);
            select.activate();   
            map.zoomToExtent(new OpenLayers.Bounds(68.774414,11.381836,123.662109,34.628906));
        }
        function onPopupClose(evt) {
            select.unselectAll();
        }
        function onFeatureSelect(event) {
            var feature = event.feature;
            // Since KML is user-generated, do naive protection against
            // Javascript.
            var content = "<h2>"+feature.attributes.name + "</h2>" + feature.attributes.description;
            if (content.search("<script") != -1) {
                content = "Content contained Javascript! Escaped content below.<br>" + content.replace(/</g, "&lt;");
            }
            popup = new OpenLayers.Popup.FramedCloud("chicken", 
                                     feature.geometry.getBounds().getCenterLonLat(),
                                     new OpenLayers.Size(100,100),
                                     content,
                                     null, true, onPopupClose);
            feature.popup = popup;
            map.addPopup(popup);
        }
        function onFeatureUnselect(event) {
            var feature = event.feature;
            if(feature.popup) {
                map.removePopup(feature.popup);
                feature.popup.destroy();
                delete feature.popup;
            }
        }
    </script>
  </head>
  <body onload="init()">
      <h1 id="title">KML Layer Example</h1>

      <div id="tags">
          kml, popup, feature
      </div>

      <p id="shortdesc">
          Demonstrates loading and displaying a KML file on top of a basemap.
    </p>

    <div id="map" class="smallmap"></div>

    <div id="docs"></div>
  </body>
</html>

It doesn;t render. I tried to change KML url to my local copy of sundial.kml (url: "http://openlayers.org/dev/examples/kml/sundials.kml", -> url: "/sundials.kml, and it didn't work either. I don't have Idea why.

Finally I want to add my own KML files, but they do not show either. What should I do?

Thanks in advance Rafal

回答1:

The reason that your local copy of sundials.kml won't render is that you're using OpenLayers.Protocol.HTTP, which won't load an address of the kind file://directory/file.kml.

But I've no idea why your posted code doesn't render. I'm currently wrestling with the same problem. All I can tell you is what else doesn't work.

The Openlayers documentation explains how a GML layer can be used to load a KML layer. Unfortunately, the code snippet they give in the documentation doesn't match their actual example, which uses a Vector layer just like most of their other KML (and GML) examples.

I copied the example code anyway, but changed the Vector layer to var layer = new OpenLayers.Layer.GML("GML", "gml/polygon.xml");, as per the documentation. Then I made local copies of Openlayers.js, polygon.xml and the .css stylesheets, and changed the urls to point to my local copies. So everything is local. 

<!DOCTYPE html> 
<html> 
    <head> 
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 
        <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0"> 
        <meta name="apple-mobile-web-app-capable" content="yes"> 
        <title>GML Doesn't Render</title> 
        <link rel="stylesheet" href="defaultstyle.css" type="text/css"> 
        <link rel="stylesheet" href="examplesstyle.css" type="text/css"> 
        <script src="OpenLayers.js"></script> 
        <script type="text/javascript">
            var map;

            function init(){
                map = new OpenLayers.Map('map');
                var wms = new OpenLayers.Layer.WMS(
                    "OpenLayers WMS", "http://vmap0.tiles.osgeo.org/wms/vmap0",
                    {layers: 'basic'}
                );

                var layer = new OpenLayers.Layer.GML("GML", "gml/polygon.xml");

                map.addLayers([wms, layer]);
                map.zoomToExtent(new OpenLayers.Bounds(
                    -3.92, 44.34, 4.87, 49.55
                ));
            }
        </script> 
    </head> 
    <body onload="init()"> 
        <div id="map" class="smallmap"></div> 
    </body> 
</html>

It doesn't work.

I also tried the suggestion from the documentation:

var layer = new OpenLayers.Layer.GML("KML", "kml/lines.kml", {
   format: OpenLayers.Format.KML,
   formatOptions: {
       'extractStyles': true
   }
});

It doesn't work.

There is even a specific example of loading "locally stored GML vector data on a basemap". It uses the same code as the documentation, so, needless to say, it doesn't work. I can't hyperlink to it because I haven't enough reputation yet to make three hyperlinks, but you can find it if you search the examples for "GML".

Openlayers has a security feature to make it difficult to load data and javascript from wildly different locations (and a workaround called "proxyhost" if you really have to do this). But I can't see how that would get involved when all the urls point to the localhost.

Please be gentle, this is my first post!

EDIT: It turns out that a) it's a browser security feature, not OpenLayers, and b) it doesn't allow a script on the localhost to load any other file on the localhost, even if you're offline. Chrome/Chromium has a command-line parameter -allow-file-access-from-files. Using this parameter, the above examples work. Other workarounds (Google them) seem tricky.



回答2:

This thread is old but I know it will still be looked at.

Try setting the projection when creating the KML layer. That worked for me.

    var kmllayer = new OpenLayers.Layer.Vector("KML", {
            projection: map.displayProjection,


标签： javascript google-maps kml openlayers
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