使用叠加完成函数获取多边形的面积

Question

我正在尝试获取多边形的面积，问题是这个想法是用户可以绘制多个多边形。

在 overlaycomplete 函数触发的那一刻，我似乎无法弄清楚如何实际引用刚刚制作的多边形。

目前我有这个...

google.maps.event.addListener(drawingManager, 'overlaycomplete', function (e) {
all_overlays.push(e);
if (e.type == 'polygon') {
//get the coordinate array of your polygon
var area = google.maps.geometry.spherical.computeArea(polygon.getPath());
console.log(area);
var overallArea = overallArea + area;
console.log(overallArea);
// Switch back to non-drawing mode after drawing a shape.
drawingManager.setDrawingMode(null);
}
});

因此，当形状完成时，形状的详细信息将添加到数组中，以便以后可以从地图中清除它们。

但是，当我尝试计算面积时，我得到这个......

引用错误：未定义多边形

为了引用并因此获得最近绘制的形状/多边形的面积，我实际上需要做什么？

Answer 1

多边形是e.overlay. 使用它来计算面积：

google.maps.event.addListener(drawingManager, 'overlaycomplete', function (e) {
all_overlays.push(e);
if (e.type == 'polygon') {
//get the coordinate array of your polygon
var area = google.maps.geometry.spherical.computeArea(e.overlay.getPath());
console.log(area);
overallArea = overallArea + area;
console.log(overallArea);
// Switch back to non-drawing mode after drawing a shape.
drawingManager.setDrawingMode(null);
}
});

概念验证小提琴

代码片段：

function initMap() {
var map = new google.maps.Map(document.getElementById('map'), {
center: {
lat: -34.397,
lng: 150.644
},
zoom: 8
});
var all_overlays = [];
var overallArea = 0;
var drawingManager = new google.maps.drawing.DrawingManager({
drawingMode: google.maps.drawing.OverlayType.POLYGON,
drawingControl: true,
drawingControlOptions: {
position: google.maps.ControlPosition.TOP_CENTER,
drawingModes: ['polygon']
}
});
drawingManager.setMap(map);
google.maps.event.addListener(drawingManager, 'overlaycomplete', function(e) {
all_overlays.push(e);
if (e.type == 'polygon') {
//get the coordinate array of your polygon
var area = google.maps.geometry.spherical.computeArea(e.overlay.getPath());
console.log(area);
overallArea = overallArea + area;
console.log(overallArea);
// Switch back to non-drawing mode after drawing a shape.
drawingManager.setDrawingMode(null);
}
});
}

html,
body,
#map {
height: 100%;
width: 100%;
margin: 0;
padding: 0;
}

<div id="map"></div>
<script src="https://maps.googleapis.com/maps/api/js?libraries=drawing&callback=initMap&key=AIzaSyCkUOdZ5y7hMm0yrcCQoCvLwzdM6M8s5qk" async defer></script>