群集上的数字不会显示

Question

我正在使用OpenLayers开发一个应用程序。

在加载过程中，我正在运行应用程序，一切都很顺利。但是，群集上显示每个群集上的犯罪数量的标签不会显示。

以下是群集的代码，其中地图正在正常加载。

 this.addCrimesToMap = function (){
        // Create a vector layers
        var vector = new OpenLayers.Layer.Vector("Features", {
            renderers: ['Canvas','SVG'],
            strategies: [
                new OpenLayers.Strategy.AnimatedCluster({
                    distance: 45,
                    animationMethod: OpenLayers.Easing.Expo.easeOut,
                    animationDuration: 20
                })
            ],
            styleMap: new OpenLayers.StyleMap({
                'default': {
                    graphicWidth: 25,
                    graphicHeight: 25,
                    label: "",

                    fontColor: "black",
                    fontSize: "12px",
                    fontFamily: "Arial",
                    fontWeight: "bold",
                    labelAlign: "c", //"l" - left, "r" - right, "c" - center , "m" - midle, "t" - top, "b" - bottom
                    labelXOffset: "15",
                    labelYOffset: "0",
                    labelOutlineColor: "white",
                    labelOutlineWidth: 3,
                    externalGraphic: "common/images/map/event_small.png",
                    display: "yes"
                }
            })
            //styleMap:  new OpenLayers.StyleMap(style)
        });
        map.addLayer(vector);

        // Create some random features
        var features = [];
        for (var i=0; i< 5000; i++) {

            var lon = Math.random() * (34.81-34.75) + 34.75;
            var lat = Math.random() * (31.28-31.21) + 31.21;

            var lonlat = new OpenLayers.LonLat(lon, lat);

            lonlat.transform(new OpenLayers.Projection("EPSG:4326"), new OpenLayers.Projection("EPSG:900913"));

            var point = new OpenLayers.Geometry.Point(lonlat.lon, lonlat.lat);

            var f = new OpenLayers.Feature.Vector(point);
            features.push(f);
        }
        vector.addFeatures(features);
    };

如果我没有使用styleMap，我只能看到没有标签的群集。

我做错了什么？