Question

这一段Javascript解析一个xml文件，其中包含起点和终点的纬度和经度坐标。我可以很好地在地图上找到标记，我遇到的问题是地图不以点为中心（最终它将调用Google Directions Service并绘制两点之间的路线，所以让地图很好地适应两个点而不是仅仅集中在其中一个点上会很好。

在使用硬编码的lat和long值创建地图的那一刻，我知道需要更改，但我已经尝试输入'startpoint'和'endpoint'无效，地图无法加载，所以我我在猜测下面的方式是不正确的。

     jQuery(document).ready(function($) {  

          downloadUrl("xml.php", function(data) {
            var xml = data.responseXML;
            var markers = xml.documentElement.getElementsByTagName("marker");
            for (var i = 0; i < markers.length; i++) {
                var name = markers[i].getAttribute("title");
                var startpoint = new google.maps.LatLng(
                    parseFloat(markers[i].getAttribute("startlat")),
                    parseFloat(markers[i].getAttribute("startlng")));
                var endpoint = new google.maps.LatLng(
                    parseFloat(markers[i].getAttribute("endlat")),
                    parseFloat(markers[i].getAttribute("endlng")));
                var html = "<b>" + name;
                var icon = customIcons || {};
                var startmarker = new google.maps.Marker({
                    map: map,
                    position: startpoint,
                    icon: icon.icon,
                    shadow: icon.shadow
                });
                bindInfoWindow(startmarker, map, infoWindow, html);
                var endmarker = new google.maps.Marker({
                    map: map,
                    position: endpoint,
                    icon: icon.icon,
                    shadow: icon.shadow
                });
                bindInfoWindow(endmarker, map, infoWindow, html);
            }
        });

        var map = new google.maps.Map(document.getElementById("map_canvas"), {
            center: new google.maps.LatLng(startpoint, endpoint),
            zoom: 13,
            mapTypeId: 'roadmap'
        });
        var infoWindow = new google.maps.InfoWindow;

    });

这是XML ...

的输出

<markers>
     <marker title="Journey" description="Lorem Ipsum..." startlat="53.403023" startlng="-2.130801" endlat="53.414257" endlng="-2.094128"/>
</markers>

Answer 1

LatLng期望latitude和longtude您希望将地图置于中心位置。这就是为什么下面的代码无效。

 center: new google.maps.LatLng(startpoint, endpoint),

显示地图中心两点之间的路线。你可以尝试找到起点和终点之间的中间点。

这是java中用于计算中间点的实现，更多信息 - Haversine_formula

public static void midPoint(double lat1,double lon1,double lat2,double lon2){

   double dLon = Math.toRadians(lon2 - lon1);

   //convert to radians
   lat1 = Math.toRadians(lat1);
   lat2 = Math.toRadians(lat2);
   lon1 = Math.toRadians(lon1);

   double Bx = Math.cos(lat2) * Math.cos(dLon);
   double By = Math.cos(lat2) * Math.sin(dLon);
   double lat3 = Math.atan2(Math.sin(lat1) + Math.sin(lat2), Math.sqrt((Math.cos(lat1) + Bx) * (Math.cos(lat1) + Bx) + By * By));
   double lon3 = lon1 + Math.atan2(By, Math.cos(lat1) + Bx);

   //print out in degrees
   System.out.println(Math.toDegrees(lat3) + " " + Math.toDegrees(lon3));
}

修改

Javascript实施

function middlePoint(lat1,lon1,lat2,lon2){ var dLon = toRad(lon2 - lon1); lat1 = toRad(lat1); lat2 = toRad(lat2); lon1 = toRad(lon1); var Bx = Math.cos(lat2) * Math.cos(dLon); var By = Math.cos(lat2) * Math.sin(dLon); var lat3 = Math.atan2(Math.sin(lat1) + Math.sin(lat2), Math.sqrt((Math.cos(lat1) + Bx) * (Math.cos(lat1) + Bx) + By * By)); var lon3 = lon1 + Math.atan2(By, Math.cos(lat1) + Bx); var middlePoint = new Object(); middlePoint.latitude=lat3; middlePoint.longitude=lon3; return middlePoint; } function toRad(Value) { return Value * Math.PI / 180; }

Answer 2

如果使用起点和终点生成边界，则可以使地图适合显示边界。

var map = new google.maps.Map(document.getElementById("map_canvas"), {
   zoom: 13,
   mapTypeId: 'roadmap'
});

var bounds = new google.maps.LatLngBounds();
bounds.extend(startpoint);
bounds.extend(endpoint);
map.fitBounds(bounds);

根据解析的XML纬度和经度值居中Google地图

2 个答案: