Javascript 谷歌地图V3：定期更新标记

我已经学习了Google Maps上的PHP/MYSQL教程

我希望每隔5秒左右从数据库中更新标记

据我所知，我需要使用Ajax定期更新标记，但我很难理解在何处添加函数以及在何处使用setTimeout等

我发现的所有其他例子都不能真正解释发生了什么，一些有用的指导将是非常棒的

这是我的代码，与Google示例相同，但有一些var更改：

---

我希望有人能帮助我

请注意，我没有测试过这个，因为我手头没有带xml的db

首先，您需要将加载函数拆分为一个初始化映射并加载domready上的标记的函数，以及一个稍后用于处理xml并更新映射的函数。这需要完成，这样您就不会在每次加载时重新初始化映射

其次，您需要决定如何处理地图上已经绘制的标记。为此，在将它们添加到地图时，需要将它们添加到数组中。在第二次更新时，您可以选择重新绘制标记以重建阵列，或者只更新现有阵列。我的示例显示了一个场景，您只需从屏幕上清除旧标记，这更简单

//global array to store our markers
    var markersArray = [];
    var map;
    function load() {
        map = new google.maps.Map(document.getElementById("map"), {
            center : new google.maps.LatLng(37.80815648152641, 140.95355987548828),
            zoom : 13,
            mapTypeId : 'roadmap'
        });
        var infoWindow = new google.maps.InfoWindow;

        // your first call to get & process inital data

        downloadUrl("nwmxml.php", processXML);
    }

    function processXML(data) {
        var xml = data.responseXML;
        var markers = xml.documentElement.getElementsByTagName("marker");
        //clear markers before you start drawing new ones
        resetMarkers(markersArray)
        for(var i = 0; i < markers.length; i++) {
            var host = markers[i].getAttribute("host");
            var type = markers[i].getAttribute("active");
            var lastupdate = markers[i].getAttribute("lastupdate");
            var point = new google.maps.LatLng(parseFloat(markers[i].getAttribute("lat")), parseFloat(markers[i].getAttribute("lng")));
            var html = "<b>" + "Host: </b>" + host + "<br>" + "<b>Last Updated: </b>" + lastupdate + "<br>";
            var icon = customIcons[type] || {};
            var marker = new google.maps.Marker({
                map : map,
                position : point,
                icon : icon.icon,
                shadow : icon.shadow
            });
            //store marker object in a new array
            markersArray.push(marker);
            bindInfoWindow(marker, map, infoWindow, html);


        }
            // set timeout after you finished processing & displaying the first lot of markers. Rember that requests on the server can take some time to complete. SO you want to make another one
            // only when the first one is completed.
            setTimeout(function() {
                downloadUrl("nwmxml.php", processXML);
            }, 5000);
    }

//clear existing markers from the map
function resetMarkers(arr){
    for (var i=0;i<arr.length; i++){
        arr[i].setMap(null);
    }
    //reset the main marker array for the next call
    arr=[];
}
    function bindInfoWindow(marker, map, infoWindow, html) {
        google.maps.event.addListener(marker, 'click', function() {
            infoWindow.setContent(html);
            infoWindow.open(map, marker);
        });
    }

    function downloadUrl(url, callback) {
        var request = window.ActiveXObject ? new ActiveXObject('Microsoft.XMLHTTP') : new XMLHttpRequest;

        request.onreadystatechange = function() {
            if(request.readyState == 4) {
                request.onreadystatechange = doNothing;
                callback(request, request.status);
            }
        };

        request.open('GET', url, true);
        request.send(null);
    }

---

请注意，我没有测试这个，因为我手头没有一个带有xml的db

首先，您需要将加载函数拆分为一个初始化映射并加载domready上的标记的函数，以及一个稍后用于处理xml并更新映射的函数。这需要完成，这样您就不会在每次加载时重新初始化映射

其次，您需要决定如何处理地图上已经绘制的标记。为此，在将它们添加到地图时，需要将它们添加到数组中。在第二次更新时，您可以选择重新绘制标记以重建阵列，或者只更新现有阵列。我的示例显示了一个场景，您只需从屏幕上清除旧标记，这更简单

//global array to store our markers
    var markersArray = [];
    var map;
    function load() {
        map = new google.maps.Map(document.getElementById("map"), {
            center : new google.maps.LatLng(37.80815648152641, 140.95355987548828),
            zoom : 13,
            mapTypeId : 'roadmap'
        });
        var infoWindow = new google.maps.InfoWindow;

        // your first call to get & process inital data

        downloadUrl("nwmxml.php", processXML);
    }

    function processXML(data) {
        var xml = data.responseXML;
        var markers = xml.documentElement.getElementsByTagName("marker");
        //clear markers before you start drawing new ones
        resetMarkers(markersArray)
        for(var i = 0; i < markers.length; i++) {
            var host = markers[i].getAttribute("host");
            var type = markers[i].getAttribute("active");
            var lastupdate = markers[i].getAttribute("lastupdate");
            var point = new google.maps.LatLng(parseFloat(markers[i].getAttribute("lat")), parseFloat(markers[i].getAttribute("lng")));
            var html = "<b>" + "Host: </b>" + host + "<br>" + "<b>Last Updated: </b>" + lastupdate + "<br>";
            var icon = customIcons[type] || {};
            var marker = new google.maps.Marker({
                map : map,
                position : point,
                icon : icon.icon,
                shadow : icon.shadow
            });
            //store marker object in a new array
            markersArray.push(marker);
            bindInfoWindow(marker, map, infoWindow, html);


        }
            // set timeout after you finished processing & displaying the first lot of markers. Rember that requests on the server can take some time to complete. SO you want to make another one
            // only when the first one is completed.
            setTimeout(function() {
                downloadUrl("nwmxml.php", processXML);
            }, 5000);
    }

//clear existing markers from the map
function resetMarkers(arr){
    for (var i=0;i<arr.length; i++){
        arr[i].setMap(null);
    }
    //reset the main marker array for the next call
    arr=[];
}
    function bindInfoWindow(marker, map, infoWindow, html) {
        google.maps.event.addListener(marker, 'click', function() {
            infoWindow.setContent(html);
            infoWindow.open(map, marker);
        });
    }

    function downloadUrl(url, callback) {
        var request = window.ActiveXObject ? new ActiveXObject('Microsoft.XMLHTTP') : new XMLHttpRequest;

        request.onreadystatechange = function() {
            if(request.readyState == 4) {
                request.onreadystatechange = doNothing;
                callback(request, request.status);
            }
        };

        request.open('GET', url, true);
        request.send(null);
    }

---

谢谢Michal，解释得很好，地图显示了，但我无法让节点显示，我的页面再次充满了感谢！请您发布您的示例xml，也许有2次更新，这样我就可以调试它了，位置不会经常更改，但活动的值将：Firebug返回：数据未定义-downloadUrlnwmxml.php，processXMLdata；它似乎无法从php脚本中获取XML数据？我编辑了脚本-我的错误行downloadUrlnwmxml.php，processXMLdata；应下载urlnwmxml.php，processXML；地图变量应该是全局的谢谢Michal，解释得很好，地图显示了，但是我不能让节点出现，我的页面再次充满了感谢！请您发布您的示例xml，也许有2次更新，这样我就可以调试它了，位置不会经常更改，但活动的值将：Firebug返回：数据未定义-downloadUrlnwmxml.php，processXMLdata；它似乎无法从php脚本中获取XML数据？我编辑了脚本-我的错误行downloadUrlnwmxml.php，processXMLdata；应下载urlnwmxml.php，processXML；和map变量的作用域应该是全局的

setInterval(function() { 
    downloadUrl("conection/cargar_tecnicos.php", function(data) {

        var xml = data.responseXML;
         markers = xml.documentElement.getElementsByTagName("marker");
         removeAllMarkers();
        for (var i = 0; i < markers.length; i++) {
              var name = markers[i].getAttribute("name");
            var fecha = markers[i].getAttribute("fecha");
            var id_android = markers[i].getAttribute("id_android");
            var celular = markers[i].getAttribute("celular");
            var id = markers[i].getAttribute("id");
            var logo = markers[i].getAttribute("logo");
            var type = markers[i].getAttribute("type");
            var point = new google.maps.LatLng(
                    parseFloat(markers[i].getAttribute("lat")),
                    parseFloat(markers[i].getAttribute("lng")));

           var html = "<div class='infowindow'>"
                        +"<br/><div style='text-align:center;'><img src="+logo+"><br/>"    
                        +"<b>" + name + "</b></div><br/>"
                        +"<br/><label><b>Celular:</b></label>" + celular+""
                        +"<br/><label><b>Id Android:</b></label>" + id_android+""
                        +"<br/><label><b>Fecha y Hora:</b></label>" + fecha+""
                        +"<br/><br/><div style='text-align:center;'><a><input style=';' id='pop' type='image' value='"+id+"' class='ASD' img src='img/vermas.png' title='Detalles'/></a></div></div>";
            var icon = customIcons[type] || {};
             marker[i] = new google.maps.Marker({ 
                position: point,
                icon: icon.icon,
                shadow: icon.shadow,
                title:name
            });

            openInfoWindow(marker[i], map, infoWindow, html);   
          marker[i].setMap(map);
        }
    });

},10000);
}
function removeAllMarkers(){// removes all markers from map
    for( var i = 0; i < marker.length; i++ ){
            marker[i].setMap(null);
}
}