为什么getProjection()在V3中不起作用

Question

根据API参考,地图对象应该有一个getProjection方法:http:
//code.google.com/apis/maps/documentation/v3/reference.html#Map

虽然在此示例中加载地图应警告x,y点,但是将值抛出为undefined.这是onload中调用的以下示例代码.

function initialize() {
 var mapOptions = {
zoom: 8,
center: new google.maps.LatLng(-34.397, 150.644),
mapTypeId: google.maps.MapTypeId.ROADMAP
};
 map = new google.maps.Map(document.getElementById('map-canvas'),
  mapOptions);
alert("projection:"+map.getProjection());
}

Answer 1

在地图完成初始化之前,它不可用.在访问之前,您必须等待"projection_changed"事件.

function initialize() {
 var mapOptions = {
   zoom: 8,
   center: new google.maps.LatLng(-34.397, 150.644),
   mapTypeId: google.maps.MapTypeId.ROADMAP
   };
 map = new google.maps.Map(document.getElementById('map-canvas'),
  mapOptions);
 google.maps.event.addListenerOnce(map,"projection_changed", function() {
   alert("projection:"+map.getProjection());
 });
}