当用户点击地图时回调此方法，如果点击在某个覆盖物（如marker、polyline）上，且处理了该点击事件，则不会回调此方法。
This method is called back when the user clicks the map. If the click is on an overlay (e.g., marker, polyline) and the click event is handled, this method will not be called back.
参数:
point - 用户所点击的地理坐标
The geographic coordinates of the user's click.