Openlayers獲取矢量圖層要素的質心並使用它來設置地圖的中心

Question

下面的代碼使用地圖中心的絕對位置，但我想根據從中引入的矢量圖層要素設置中心KML文件 - 這可能嗎？我已經看過getCentroid，但無法獲得正確的語法？

map = new OpenLayers.Map("Map"); 
var mapnik = new OpenLayers.Layer.OSM(); 
//Set centre position converting from WGS to Mercator 
var wgs84 = new OpenLayers.Projection("EPSG:4326"); 
var fromProjection = new OpenLayers.Projection("EPSG:4326"); // Transform from WGS 1984 
var toProjection = new OpenLayers.Projection("EPSG:900913"); // to Spherical Mercator Projection 
var position  = new OpenLayers.LonLat(4.891280,52.373690).transform(fromProjection, toProjection); 

var layer = new OpenLayers.Layer.Vector("vectorlayer", { 
    projection: wgs84, 
    strategies: [new OpenLayers.Strategy.Fixed()], 
    protocol: new OpenLayers.Protocol.HTTP({ 
     url: "kmlfile.kml", //<-- relative or absolute URL to your .osm file 
     format: new OpenLayers.Format.KML() 
    }), 
    styleMap: new OpenLayers.StyleMap({ 
     "default": { 
      //pointRadius: "${radius}", 
      fillColor: "blue", 
      fillOpacity: 0.1, 
      strokeColor: "#5555ff", 
      strokeWidth: 2, 
      strokeOpacity: 0.8 
     } 
     , 
     "select": { 
      fillColor: "#8aeeef", 
      strokeColor: "#32a8a9" 
     } 
    }) 
}); 

map.addLayers([mapnik, layer]); 

map.addControl(new OpenLayers.Control.LayerSwitcher()); 

var scaleline = new OpenLayers.Control.ScaleLine(); 
map.addControl(scaleline); 


//Set centre of map and zoom level 
map.setCenter(position, 10); 

Answer 1

試試這個（其中一層是你的載體基於您的代碼）：

var bounds = layer.geometry.bounds; 
map.zoomToExtent(bounds); 

或

var bounds = layer.geometry.bounds; 
map.setCenter(bounds.getCenterLonLat());