由于 KmlGroundOverlays 尚未生成鼠标事件，另一种解决方法是从地球接收鼠标事件，然后确定鼠标是否在覆盖范围内（“命中测试”）。下面是使用 mouseMove 事件执行此操作的代码的起点。它生成两个重叠的覆盖（一个旋转）并将鼠标下的覆盖带到表面（通过操纵drawingOrder）。
它在自己的结构中维护有关叠加层的信息（而不是遍历 KML，这可能是可能的）。
我无法找到从 GE 获取旋转叠加层顶点位置的方法，因此旋转是在代码中使用笛卡尔近似值完成的。此代码可能会在极点或边界或大多边形上中断。
一旦知道顶点，在鼠标移动上运行的命中测试基于如何确定 2D 点是否在多边形内？
因此，此代码说明了以下方面的起始想法：
- 如何从叠加层合成鼠标事件（一种解决方法，直到 KML 叠加层可以生成鼠标事件）
- 如何近似旋转叠加层的顶点（找到叠加层的位置）
- 对叠加层进行命中测试（来自上述参考）
- 使用 drawOrder 在鼠标悬停时将重叠的叠加层带到表面
在http://jsfiddle.net/pudkg/有一个演示
这是代码和html：
<!DOCTYPE html>
<html>
<head>
<script type="text/javascript" src="https://www.google.com/jsapi"> </script>
<script type="text/javascript">
var ge;
var overlays = []; // record information about overlays (filled by 'addOverlay')
var drawOrder = 0; // drawOrder value of topmost overlay
google.load("earth", "1");
function Point (lat, lon) {
this.lat = lat;
this.lon = lon;
}
function Overlay (groundOverlay, points, drawOrder) {
this.overlay = groundOverlay; // KML object
this.points = points; // array of Points (vertices of overlay)
this.drawOrder = drawOrder; // integer, higest displayed topmost
}
Overlay.prototype.hitTest = function (lat, lon) { // return true if lat/lon is within overlay
// Based upon https://stackoverflow.com/questions/217578/point-in-polygon-aka-hit-test
var isInside = false;
var minLon = this.points[0].lon, maxLon = this.points[0].lon;
var minLat = this.points[0].lat, maxLat = this.points[0].lat;
for (var n = 1; n < this.points.length; n++) {
var q = this.points[n];
minLon = Math.min(q.lon, minLon);
maxLon = Math.max(q.lon, maxLon);
minLat = Math.min(q.lat, minLat);
maxLat = Math.max(q.lat, maxLat);
}
if (lon < minLon || lon > maxLon || lat < minLat || lat > maxLat)
return false;
var i = 0, j = this.points.length - 1;
for (i, j; i < this.points.length; j = i++)
if ( (this.points[i].lat > lat) != (this.points[j].lat > lat) &&
lon < (this.points[j].lon - this.points[i].lon) * (lat - this.points[i].lat) /
(this.points[j].lat - this.points[i].lat) + this.points[i].lon )
isInside = !isInside;
return isInside;
}
function init() {
google.earth.createInstance('map3d', initCB, failureCB);
}
function initCB(e) {
ge = e;
ge.getWindow().setVisibility(true);
var lat = 37.204193;
var lon = -112.934429;
var dlat = 0.003;
var dlon = 0.005;
var offset = 0.004;
var la = ge.createLookAt(''); // position camera
la.set(lat, lon, 0, ge.ALTITUDE_RELATIVE_TO_GROUND, 0, 30, 2000);
ge.getView().setAbstractView(la);
for (var i = 0; i < 2; i++) // generate two overlays, overlapping; second one rotated
addOverlay('http://www.google.com/logos/earthday08.gif',
lat + dlat + offset*i, lat - dlat + offset*i,
lon + dlon + offset*i, lon - dlon + offset*i, 30*i);
// KML overlays can't (yet) generate mouse events, so look for events from globe
google.earth.addEventListener(ge.getGlobe(), 'mousemove', function(event) {
var lat = event.getLatitude();
var lon = event.getLongitude();
// show that a move event was received:
document.getElementById('logMove').innerHTML = event.getLatitude();
topmost = -1, zMax = 0; // find topmost overlay
for (var i = overlays.length - 1; i >= 0; i--)
if (overlays[i].hitTest(lat, lon)) { // if mouse is within overlays[i]
document.getElementById('logHit').innerHTML = i + '; ' + overlays[i].drawOrder;
if (overlays[i].drawOrder > zMax) { // if this overlay is higher than any previous
topmost = i;
zMax = overlays[i].drawOrder;
}
}
if ((topmost >= 0) && (overlays[topmost].drawOrder < drawOrder)) {
// if in an overlay and it is buried, make it top-most
overlays[topmost].overlay.setDrawOrder(++drawOrder);
overlays[topmost].drawOrder = drawOrder; // update local structure
}
document.getElementById('logOver').innerHTML = topmost + '; ' + zMax;
});
}
function addOverlay(url, north, south, east, west, rotation) {
var groundOverlay = ge.createGroundOverlay(''); // create overlay
var icon = ge.createIcon('');
icon.setHref(url);
groundOverlay.setIcon(icon);
var latLonBox = ge.createLatLonBox('');
latLonBox.setBox(north, south, east, west, rotation);
groundOverlay.setLatLonBox(latLonBox);
groundOverlay.setDrawOrder(++drawOrder);
ge.getFeatures().appendChild(groundOverlay);
var points = []; // figure out lat/lon of the corners of the overlay
var sinTheta = Math.sin(rotation * Math.PI / 180.0);
var cosTheta = Math.cos(rotation * Math.PI / 180.0);
// rotation is about the center of the overlay; find midpoint:
var midPoint = new Point((north + south) / 2, (west + east) / 2);
// To do cartesian rotation, need to consider that the distance between
// units of longitude diminish as one goes north, to zero at pole:
var cosLat = Math.cos(midPoint.lat * Math.PI / 180.0); // longitude compression factor
west = (west - midPoint.lon) * cosLat, east = (east - midPoint.lon) * cosLat;
north -= midPoint.lat, south -= midPoint.lat;
// use cartesian rotation (good enough approximation for UI away from pole, boundaries)
// after rotation, restore (expand) longitudes by compression factor
points.push(new Point(midPoint.lat + west * sinTheta + north * cosTheta,
midPoint.lon + (west * cosTheta - north * sinTheta) / cosLat));
points.push(new Point(midPoint.lat + east * sinTheta + north * cosTheta,
midPoint.lon + (east * cosTheta - north * sinTheta) / cosLat));
points.push(new Point(midPoint.lat + east * sinTheta + south * cosTheta,
midPoint.lon + (east * cosTheta - south * sinTheta) / cosLat));
points.push(new Point(midPoint.lat + west * sinTheta + south * cosTheta,
midPoint.lon + (west * cosTheta - south * sinTheta) / cosLat));
overlays.push(new Overlay(groundOverlay, points, drawOrder));
}
function failureCB(errorCode) {
alert("GE init fail");
}
google.setOnLoadCallback(init);
</script>
</head>
<body>
<div id=map3d style='height: 400px; width: 600px'></div>
<p>Mouse over the two overlays. The one under the mouse should come to surface.</p>
<p>Latitude of mouse: <span id=logMove></span></p>
<p>Index of last overlay hit; its drawOrder: <span id=logHit></span></p>
<p>Index of topmost overlay; max drawOrder: <span id=logOver></span></p>
</body>
</html>