Android 判断是否能真正上网

     * @author suncat
     * @category 判断是否有外网连接（普通方法不能判断外网的网络是否连接，比如连接上局域网）
     * @return
     */ 
    public static final boolean ping() { 
   
        String result = null; 
        try { 
                String ip = "www.baidu.com";// ping 的地址，可以换成任何一种可靠的外网 
                Process p = Runtime.getRuntime().exec("ping -c 3 -w 100 " + ip);// ping网址3次 
                // 读取ping的内容，可以不加 
                InputStream input = p.getInputStream(); 
                BufferedReader in = new BufferedReader(new InputStreamReader(input)); 
                StringBuffer stringBuffer = new StringBuffer(); 
                String content = ""; 
                while ((content = in.readLine()) != null) { 
                        stringBuffer.append(content); 
                } 
                Log.d("------ping-----", "result content : " + stringBuffer.toString()); 
                // ping的状态 
                int status = p.waitFor(); 
                if (status == 0) { 
                        result = "success"; 
                        return true; 
                } else { 
                        result = "failed"; 
                } 
        } catch (IOException e) { 
                result = "IOException"; 
        } catch (InterruptedException e) { 
                result = "InterruptedException"; 
        } finally { 
                Log.d("----result---", "result = " + result); 
        } 
        return false;