android判断正在使用的网络类型 0.不知道网络类型；1、2G；2、3G；3、4g；4、wifi

判断正在使用的网络类型 0.不知道网络类型；1、2G；2、3G；3、4g；4、wifi

     /** Unknown network class. {@hide} */
     public static final String NETWORK_CLASS_UNKNOWN = "0";
     /** Class of broadly defined "2G" networks. {@hide} */
     public static final String NETWORK_CLASS_2_G = "1";
     /** Class of broadly defined "3G" networks. {@hide} */
     public static final String NETWORK_CLASS_3_G = "2";
     /** Class of broadly defined "4G" networks. {@hide} */
     public static final String NETWORK_CLASS_4_G = "3";
     /** Class of broadly defined "wifi" networks. {@hide} */
     public static final String NETWORK_CLASS_WIFI = "4";
     /**
      * 判断正在使用的网络类型 0.不知道网络类型；1、2G；2、3G；3、4g；4、wifi
      * @param context
      * @return
      */
     public static String getNet(Context context) {
         try {
             ConnectivityManager manager = (ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);
             State mobile = manager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE).getState();
             State wifi = manager.getNetworkInfo(ConnectivityManager.TYPE_WIFI).getState();
             if(mobile == State.CONNECTED||mobile==State.CONNECTING) {
                 NetworkInfo info = manager.getActiveNetworkInfo();
                 int type = info.getSubtype();
                 switch (type) {
                 case TelephonyManager.NETWORK_TYPE_GPRS:
                 case TelephonyManager.NETWORK_TYPE_EDGE:
                 case TelephonyManager.NETWORK_TYPE_CDMA:
                 case TelephonyManager.NETWORK_TYPE_1xRTT:
                 case TelephonyManager.NETWORK_TYPE_IDEN:
                     return NETWORK_CLASS_2_G;
                 case TelephonyManager.NETWORK_TYPE_UMTS:
                 case TelephonyManager.NETWORK_TYPE_EVDO_0:
                 case TelephonyManager.NETWORK_TYPE_EVDO_A:
                 case TelephonyManager.NETWORK_TYPE_HSDPA:
                 case TelephonyManager.NETWORK_TYPE_HSUPA:
                 case TelephonyManager.NETWORK_TYPE_HSPA:
                 case TelephonyManager.NETWORK_TYPE_EVDO_B:
                 case TelephonyManager.NETWORK_TYPE_EHRPD:
                 case TelephonyManager.NETWORK_TYPE_HSPAP:
                     return NETWORK_CLASS_3_G;
                 case TelephonyManager.NETWORK_TYPE_LTE:
                     return NETWORK_CLASS_4_G;
                 default:
                     return NETWORK_CLASS_UNKNOWN;
                 }
             }
             else if(wifi == State.CONNECTED||wifi==State.CONNECTING) {
                 return NETWORK_CLASS_WIFI;
             }
         } catch (Exception e) {
             LogUtil.e(tag, e);
             return NETWORK_CLASS_UNKNOWN;
         }
         return NETWORK_CLASS_UNKNOWN;
     }