如何在google地图的折线中心设置折线标记？

// 创建地图实例
var map = new google.maps.Map(document.getElementById('map'), {
  center: {lat: 37.7749, lng: -122.4194},
  zoom: 12
});

// 创建折线对象
var line = new google.maps.Polyline({
  path: [
    {lat: 37.7749, lng: -122.4194},
    {lat: 37.7895, lng: -122.4147},
    {lat: 37.7749, lng: -122.4342}
  ],
  strokeColor: '#FF0000',
  strokeOpacity: 1.0,
  strokeWeight: 2
});

// 计算折线的中心点坐标
var startPoint = line.getPath().getAt(0);
var endPoint = line.getPath().getAt(line.getPath().getLength() - 1);
var centerPoint = google.maps.geometry.spherical.computeDistanceBetween(startPoint, endPoint);

// 创建折线标记对象
var marker = new google.maps.Marker({
  position: centerPoint,
  map: map,
  title: '折线中心'
});