如何使用 Leaflet.draw 从多边形中获取区域字符串

2022-01-12 00:00:00 leaflet javascript

我正在尝试获取多边形的面积测量值，以便可以将它们列在地图一侧的表格中，靠近多边形的名称.这是我尝试过但没有成功的方法:

I am trying to get the area measurements of polygons so I can list them in a table to the side of the map, next to the name of the polygon. This is what I have tried with no success:

$("#polygon").on("click", function (){
    createPolygon = new L.Draw.Polygon(map, drawControl.options.polygon);
    createPolygon.enable();
}

var polygon = new L.featureGroup();

map.on('draw:created', function (e) {
    var type = e.layerType,
        layer = e.layer;
    if (type === 'polygon') {
      polygons.addLayer(layer);
    }
    var seeArea = createPolygon._getMeasurementString();
   console.log(seeArea);  //Returns null
}

对此的任何帮助将不胜感激！

Any help on this would be appreciated!

推荐答案

您可以访问 Leaflet 提供的几何实用程序库.

You can access the geometry utility library provided with Leaflet.

var area = L.GeometryUtil.geodesicArea(layer.getLatLngs());

在您的示例中，您尝试访问控件本身，这是变量 createPolygon 分配给的内容.相反，您想要获取已绘制图层的区域.

In your example, you are trying to access a control itself, which is what the variable createPolygon is assigned to. Instead, you want to take the area of the layer that got drawn.

map.on('draw:created', function (e) {
  var type = e.layerType,
      layer = e.layer;
  if (type === 'polygon') {
    polygons.addLayer(layer);
    var seeArea = L.GeometryUtil.geodesicArea(layer.getLatLngs());
    console.log(seeArea);
  }
}

确认您获得了该区域后，您只需将其分配给填充地图旁边表格的变量即可.

Once you verify you are getting the area, you can just assign it to the variables that populate the table next to the map.

注意:面积默认为平方米

Note: area will be in squareMeters by default

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