OpenLayers - 如何从现有的 lonLat 点绘制多边形？

Question

我的数据库中有来自用户定义多边形的经纬度顶点。我的问题是：我现在如何在地图上重新创建和显示它们？使用 Google Maps API 很容易做到这一点，但我找不到任何关于如何使用 OpenLayers 做到这一点的文档或示例。有没有人有这样做的经验？

Answer 1

经过大量实验，我发现了如何做到这一点：

let sitePoints = [];
let siteStyle = {
  // style_definition
};

let epsg4326 = new OpenLayers.Projection("EPSG:4326");
for (let i in coordinates) {
  let coord = coordinates[i];
  let point = new OpenLayers.Geometry.Point(coord.lng, coord.lat);
  // transform from WGS 1984 to Spherical Mercator
  point.transform(epsg4326, map.getProjectionObject());
  sitePoints.push(point);
}
sitePoints.push(sitePoints[0]);

let linearRing = new OpenLayers.Geometry.LinearRing(sitePoints);
let geometry = new OpenLayers.Geometry.Polygon([linearRing]);
let polygonFeature = new OpenLayers.Feature.Vector(geometry, null, siteStyle);
vectors.addFeatures([polygonFeature]);

Answer 2

OpenLayers 6

OpenLayers 6 稍有不同，需要一段时间才能弄清楚。所以我把OL6的相关代码贴在这里。

coordinates 属于 [[[number]]] 类型（这是多边形的 GeoJson 标准）。

styles 超出范围（如果有人感兴趣，我可以将其粘贴到此处，但每个应用程序的定义可能不同）。

var VectorSource = ol.source.Vector;
var {Tile, Vector} = ol.layer; //import {Tile as TileLayer, Vector as VectorLayer} from 'ol/layer.js';
var TileLayer = Tile;
var VectorLayer = Vector;

var map = new ol.Map(...);

function drawPolygonOnMap(coordinates) {
    const polygonFeature = new ol.Feature(
        new ol.geom.Polygon(coordinates).transform('EPSG:4326','EPSG:3857'));


    let source = new VectorSource({
      features: [polygonFeature]
    });

    var layer = new VectorLayer({
      source: source,
      style: styles
    });

    map.addLayer(layer);
}