基本原理是: send http request to google direction api url (http://maps.google.com/maps/api/directions/json?xxx) parse the response, and then draw it.
google direction api user guide: http://code.google.com/intl/zh-TW/apis/maps/documentation/directions/
http://www.dotblogs.com.tw/alonstar/archive/2011/05/26/26282.aspx
http://www.dotblogs.com.tw/alonstar/archive/2011/05/26/26310.aspxhttp://www.dotblogs.com.tw/alonstar/archive/2011/05/26/26303.aspx
http://www.dotblogs.com.tw/alonstar/archive/2011/05/27/26342.aspx
http://blog.youkuaiyun.com/ccgang/article/details/6328671
http://stackoverflow.com/questions/6708408/map-view-draw-directions-using-google-directions-api-decoding-polylines
http://stackoverflow.com/questions/3109158/how-to-draw-a-path-on-a-map-using-kml-file/3109723#3109723
http://www.360doc.com/content/11/1015/11/7635_156342833.shtml
http://www.linuxidc.com/Linux/2011-05/36375p2.htm
http://hi.baidu.com/neverever888/blog/item/ae37721df7fe91ed1ad57692.html
http://blog.xuite.net/misgarlic/weblogic/39756767