无法在更改事件中获得不同的图标

你去...我为您修复了您的代码...你有一些错误。 最大的问题是您没有将创建的标记保存到数组中以在事件侦听器上循环。

我添加了 gMarker 数组。 我在您网站的控制台中运行了代码，它起作用了。 如果您有任何问题，请告诉我。

 var infowindow;
 var map;
 var gMarkers=[];
  function initialize() {
    var myLatlng = new google.maps.LatLng(20, 0);
    var myOptions = {
        zoom: 3,
        panControl:true,
        zoomControl:true,
        mapTypeControl:true,
        scaleControl:true,
        streetViewControl:true,
        overviewMapControl:true,
        rotateControl:true,    
        center: myLatlng,
        mapTypeId: google.maps.MapTypeId.ROADMAP
    };
    map = new google.maps.Map(document.getElementById("map_canvas"), myOptions);
    downloadUrl("worldcities.xml", function(data) {
        markers = data.documentElement.getElementsByTagName("marker");
    });
    for (var i = 0; i < markers.length; i++) {
        var latlng = new google.maps.LatLng(parseFloat(markers[i].getAttribute("lat")),parseFloat(markers[i].getAttribute("lng")));
        var circleOptions = {
            strokeColor: '#FF0000',
            strokeOpacity: 0.65,
            strokeWeight: 2,
            fillColor: '#FF0000',
            fillOpacity: 0.25,
            map: map,
            center: latlng,
            radius: parseInt(markers[i].getAttribute("population"))/25
        };
        gMarkers.push(createMarker(markers[i].getAttribute("name"), latlng,markers[i].getAttribute("population"), markers[i].getAttribute("countrycode"), markers[i].getAttribute("region")));
        var onekmcircle = new google.maps.Circle(circleOptions);    
    }

    google.maps.event.addListener(map, 'zoom_changed', function() {
        var url ='http://maps.google.com/mapfiles/ms/icons/red-dot.png';
        var icon = google.maps.MarkerImage(url);
        var currentZoom = map.getZoom();
          if (currentZoom >9){
            for(var i=0; i< gMarkers.length; i++ ) {
                gMarkers[i].setIcon(icon);
            }
          }else{
                for(var i=0; i< gMarkers.length; i++ ) {
                    gMarkers[i].setIcon({path: google.maps.SymbolPath.CIRCLE,scale: 2});
                }
          }
    });
 }

function createMarker(name, latlng, popl, cntry, rgon) {
    marker = new google.maps.Marker({
        position: latlng, 
        map: map,
        icon: {
            path: google.maps.SymbolPath.CIRCLE,
            scale: 2
        }, 
        title: name
    });
    var contentstring = '<b>'+name+'</b>'+'<br>Population: '+popl+'<br>Country: '+cntry+'<br>Region: '+rgon;
    google.maps.event.addListener(marker, "click", function() {
        if (infowindow) infowindow.close();
        infowindow = new google.maps.InfoWindow({content: contentstring});
        infowindow.open(map, marker);
        var zoomLevel = map.getZoom();
        map.setCenter(marker.getPosition());
        if (zoomLevel<6){
            map.setZoom(6);
        }
    });
    return marker;
}

google.maps.event.addListener(marker,''mouseover'', function() {
    marker.setIcon("fileadmin/new_templates/images/home_map_notification_hover.png");
    $.ajax({
    type: "POST",
    async : false,
    data: ''address=''+add ,
    success: function(html){
            infowindow.setContent(html); 
            infowindow.open(map,marker);
        },
    });
});
// On Mouse out
google.maps.event.addListener(infowindow, ''mouseout'', function () {
marker.setIcon("fileadmin/new_templates/images/home_page_map_notification.png");
});
// On Infowindow close
google.maps.event.addListener(infowindow, ''closeclick'', function () {
marker.setIcon("fileadmin/new_templates/images/home_page_map_notification.png");
});