OL3: Zoom to vector layer on map

Question

I have a map with openlayers 3 and a vector layer. I want to map to be resized to this vector layer, but so far all I was able to get was to center the map on the last point of this vector, since the points of the vector layer are not accessible while creating the map:

if (trackMap != null) {
  for (var i = 0; i < trackMap.length; i++) {
    var trackInfo = trackMap[i];
    lat = parseFloat(trackInfo.lat);
    lon = parseFloat(trackInfo.lon);

    var layergpx = new ol.layer.Vector({
      source: new ol.source.Vector({
        parser: new ol.parser.GPX(),
        url: '${contextRoot}/gps/gpx2' + trackInfo.url
      })
    });
    layers.push(layergpx);
    vectorLayers.push(layergpx);
  }
}

map = new ol.Map({
  controls: ol.control.defaults().extend([
    new ol.control.FullScreen()
  ]),
  layers: layers,
  renderer: ol.RendererHint.CANVAS,
  target: 'map',
  view: new ol.View2D({
    center: ol.proj.transform([lon, lat], 'EPSG:4326', 'EPSG:3857'),
    zoom: 13
  })
});

Answer 1

So... after a few days of testing and thinking I solved the problem. Not without further problems, but calculating the borders serverside and transmitting them to the script made it a bit easier.

The Javascript is fairly short for solving the problem:

if (minLon != null && minLat != null && maxLon != null && maxLat != null){
 var bottomLeft = ol.proj.transform([minLon, minLat], 'EPSG:4326', 'EPSG:3857');
 var topRight = ol.proj.transform([maxLon, maxLat], 'EPSG:4326', 'EPSG:3857');
 extent = new ol.extent.boundingExtent([bottomLeft,topRight]);
 map.getView().fitExtent(extent, map.getSize());
}

Answer 2

Why not just fit to the extent of the ol.source.Vector?

var source = new ol.source.Vector();

...

map.getView().fitExtent(source.getExtent(), map.getSize());

Answer 3

From version 3.7.0 ol.View.fitExtent() was replaced by ol.View.fit()

var source = new ol.source.Vector();
map.getView().fit(source.getExtent(), map.getSize());

Answer 4

I have a way of doing the view centering without worrying about transforming the degrees from one standard to another. Wondering this trick would apply to you. You first get the extents from all your sources. Factorizing their center and input that center to your viewport:

try {
    extentEMRG = geoSrcEMRG.getExtent();
    extentWARN = geoSrcWARN.getExtent();
    ext2Layers = ol.extent.getIntersection(extentEMRG, extentWARN);
    center2Layers = ol.extent.getCenter(ext2Layers);
    //alert(center2Layers);
} catch (e) {
    alert(e.message);
}
 var map = new ol.Map({
    view: new ol.View({
        center: center2Layers
        , zoom: 8
    })
    , layers: [
        new ol.layer.Tile({
            source: new ol.source.OSM()
        })
        , vLayerWARN 
        , vLayerEMRG 
    ] ....