谷歌离线地图的使用(1)

实质： 整个地图都是以由 小的地图瓦片组成的，因此可以将这些小瓦片图片保存下来，在需要的时候读取即可。

过程： 客户端将地图的三维坐标发送回服务器，服务器经过计算后，返回对应的 图片。

API 下载地址： http://download.youkuaiyun.com/detail/iamwangch/4933837

Google的离线地图并未真正意义上的离线，由于代码过于凌乱，无法正确解读，所以采用了添加本地服务器的方法实现离线

 过程： 

• (一)创建项目并添加GoogleMapAPIV3 文件包

下载地址： http://www.cnblogs.com/liongis/archive/2011/04/28/2032316.html

• (二)修改文件包内的mapapi.js的myUrl变量为项目登录网址如：http：           hostlocal：8080/xx
• (三)响应请求 项目获取有js发出的一个action的请求 如：

http://"+myUrl+"/mt0/vt.action?lyrs=m@152&src=apiv3&hl=zh-CN&x=216&y=104&z=8&s=

上面的请求有x，y，z的三个参数传进来，这三个参数就是地图瓦片的值

根据这三个参数传回瓦片图片即可。

• (四)经纬度 转换到 图片坐标

参考： http://code.google.com/intl/zh-CN/apis/maps/documentation/javascript/overlays.html#CustomMapTypes

 

服务器代码

下载

---

/**

       * 保存文件

       */

        private  void  SaveImage( int  x,  int  y, int  z,String basePath){

            String outPath = basePath+  "/" +x+ "-"  +y+ "-" +z+  ".png" ;

            String urlStr =  "http://mt1.googleapis.com/vt?lyrs=m@203000000&src=apiv3&hl=zh-CN&"  +

                          "x="  +x+

                          "&y="  +y+

                          "&z="  +z+

                          "&s=Galileo&style=api%7Csmartmaps"  ;

              int  chByte = 0;         

            URL url =  null ;         

            HttpURLConnection httpConn =  null ;        

            InputStream in =  null ;        

            FileOutputStream out =  null ;        

              try  {                   

                  url =  new  URL(urlStr);              

                  httpConn = (HttpURLConnection)

                  url.openConnection();               

                  HttpURLConnection. setFollowRedirects( true );                 

                  httpConn.setRequestMethod(  "GET" );               

                  httpConn.setRequestProperty(  "User-Agent" ,                               

                                "Mozilla/4.0 (compatible; MSIE 6.0; Windows 2000)" );              

                    // logger.info(httpConn.getResponseMessage());              

                  in = httpConn.getInputStream();                 

                  out =  new  FileOutputStream( new  File(outPath));              

                  chByte = in.read();                 

                    while  (chByte != -1) {                    

                        out.write(chByte);                        

                        chByte = in.read();                 

                        }           

                  }  catch  (MalformedURLException e) {                   

                        e.printStackTrace();          

                        }  catch  (IOException e) {                 

                              e.printStackTrace();    

                              }

            }

---

返回客户端

---

public  String doLoad()  throws  IOException {

            HttpServletRequest request = ServletActionContext.getRequest();

            HttpServletResponse response = ServletActionContext.getResponse();

            String basePath  =  "" ;   //基本路径

            basePath = request.getSession().getServletContext().getRealPath( "/map-images"  );

              //System.out.println("基本路径 ->"+basePath);

            System.  out .println( "坐标： x:"  +  x  +  " y:"  +  y  +  " z:"  +  z  );

            ByteArrayOutputStream byteArrayOutputStream =  new  ByteArrayOutputStream();

            

            

            String path = basePath+  "/" + x  + "-"  + y  + "-"  + z  + ".png"  ;

            File file =  new  File(path);  // 读取指定路径的图片

            

            

            InputStream in =  null ;

              try  {

                  in =  new  FileInputStream(file);

            }  catch  (FileNotFoundException e) {

                    this .SaveImage( x  ,  y  ,  z  , basePath);

                  in =  new  FileInputStream(file);

                    //e.printStackTrace();

                  System.  out .println( "文件不存在，需要下载."  );

            }

              int  tag = 0;

              byte [] b =  new  byte [100];

              while  ((tag = in.read(b))!=-1) {

                    //System.out.println("读取到的大小："+tag);

                  byteArrayOutputStream.write(b, 0, tag);

            }

            

              this . imageStream  =  new  ByteArrayInputStream(byteArrayOutputStream.toByteArray());

            

              return  "success"  ;

      }