如何获取GeoJSON向量源的范围? [英] How to get the extent of a GeoJSON vector source?

问题描述

我有这个GeoJSON文件(polygon.geojson)...

I have this GeoJSON file (polygon.geojson)...

{
  "type": "Feature",
  "geometry": { "type": "Polygon", "coordinates": [ [ [73, 15], [83.0, 15], [83, 5], [73, 5], [73, 15] ] ] },
  "properties": { "name": "Foo" }
}

...并将其用作矢量源:

...and use it as vector source:

var vectorSource = new ol.source.Vector({
    url: 'polygon.geojson',
    format: new ol.format.GeoJSON(),
    projection : 'EPSG:4326',
});

现在我想了解范围:

var extent = vectorSource.getExtent();

extent的值是:

Array [ Infinity, Infinity, -Infinity, -Infinity ]

我使用的是OL 3.9.0，带有此源的矢量层显示正确.我在做什么错了?

I'm using OL 3.9.0 and the vector layer with this source is displayed properly. What am I doing wrong?

推荐答案

我知道了.我需要等到源被加载:

I figured it out. I need to wait until the source is loaded:

vectorSource.once('change',function(e){
    if(vectorSource.getState() === 'ready') {
        var extent = vectorSource.getExtent();
        console.log(extent);
        map.getView().fit(extent, map.getSize());
    }
});

编辑:仅当图层不为空时，缩放才可能更安全:

It might be safer to zoom only if the layer isn't empty:

vectorSource.once('change',function(e){
    if(vectorSource.getState() === 'ready') { 
        if(layers[0].getSource().getFeatures().length>0) {
            map.getView().fit(vectorSource.getExtent(), map.getSize());
        }
    }
});

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