如何在Amcharts中点击map Bubble并调用服务器请求

// 创建地图实例
var map = am4core.create("mapDiv", am4maps.MapChart);

// 设置地图配置
map.geodata = am4geodata_worldLow;
map.projection = new am4maps.projections.Miller();

// 创建地图系列
var series = map.series.push(new am4maps.MapPolygonSeries());
series.useGeodata = true;

// 创建Bubble图层
var bubbleSeries = map.series.push(new am4maps.MapImageSeries());
var bubbleTemplate = bubbleSeries.mapImages.template;
var circle = bubbleTemplate.createChild(am4core.Circle);

// 设置Bubble图层的点击事件
circle.events.on("hit", function(event) {
  // 发送服务器请求
  var xhr = new XMLHttpRequest();
  xhr.open("GET", "https://example.com/api/data", true);
  xhr.setRequestHeader("Content-Type", "application/json");
  xhr.onreadystatechange = function() {
    if (xhr.readyState === 4 && xhr.status === 200) {
      // 处理服务器响应
      var response = JSON.parse(xhr.responseText);
      console.log(response);
    }
  };
  xhr.send();
});

// 其他地图配置和数据绑定等代码...

// 启动地图
map.chartContainer.wheelable = false;