Android7.1下修改apns_conf.xml如何替换

最近遇到一个问题，4G联通卡ifconfig找不到，也无法上网

vendor/qcom/proprietary/telephony-apps/etc/apns-conf.xml增加下面的内容就可以了

 <apn carrier="China Mobile"
     apn=""
     mcc="460"
     mnc="04"
     user=""
     server=""
     password=""
     proxy=""
     port=""
     mmsproxy=""
     mmsport=""
     mmsc=""
     type="ia"
     protocol="IPV4V6"
     roaming_protocol="IPV4V6"/>
 
 <apn carrier="China Mobile"
     apn="cmnet"
     mcc="460"
     mnc="04"
     user=""
     server=""
     password=""
     proxy=""
     port=""
     mmsproxy=""
     mmsport=""
     mmsc=""
     type="default,net,supl"
     preferred="true"
     localized_name="APN_NAME_CMNET"
     protocol="IPV4V6"
     roaming_protocol="IPV4V6"/>
 
 <apn carrier="China Mobile MMS"
     apn="cmwap"
     mcc="460"
     mnc="04"
     user=""
     server=""
     password=""
     proxy="10.0.0.172"
     port="80"
     mmsproxy="10.0.0.172"
     mmsport="80"
     mmsc="http://mmsc.monternet.com"
     type="mms"
     localized_name="APN_NAME_CMMMS"
     protocol="IPV4V6"
     roaming_protocol="IPV4V6"/>
 
 <apn carrier="China Mobile WAP"
     apn="cmwap"
     mcc="460"
     mnc="04"
     proxy="10.0.0.172"
     port="80"
     type="default,supl,wap"
     localized_name="APN_NAME_CMWAP"
     protocol="IPV4V6"
     roaming_protocol="IPV4V6"/>
        
 <!-- -LTE ctlte for China MainLand -->
 <apn carrier="China Telecom"
     apn="ctlte"
     mcc="460"
     mnc="05"
     user=""
     server=""
     password=""
     proxy=""
     port=""
     mmsproxy=""
     mmsport=""
     mmsc=""
     protocol="IPV4V6"
     roaming_protocol="IPV4V6"
     type="ia"/>
 
 <!-- CTWAP for China MainLand-->
 <apn carrier="China Telecom"
      apn="CTWAP"
     mcc="460"
     mnc="05"
     user="ctwap@mycdma.cn"
     server=""
     password="vnet.mobi"
     proxy=""
     port=""
     mmsproxy=""
     mmsport=""
     mmsc=""
     type="default,supl"
     authtype="3"
     ppp_number="#777"
     localized_name="APN_NAME_CTWAP"
     read_only ="true"
     protocol="IPV4V6"
     roaming_protocol="IPV4V6"
     visit_area="460"/>
 
 <!-- CTNET-->
 <apn carrier="China Telecom"
     apn="CTNET"
     mcc="460"
     mnc="05"
     user="ctnet@mycdma.cn"
     server=""
     password="vnet.mobi"
     proxy=""
     port=""
     mmsproxy=""
     mmsport=""
     mmsc=""
     type="default,hipri"
     authtype="3"
     ppp_number="#777"
     read_only ="true"
     protocol="IPV4V6"
     localized_name="APN_NAME_CTNET"/>
        
 <apn carrier="China Unicom"
     apn="3gnet"
     mcc="460"
     mnc="06"
     user=""
     server=""
     password=""
     proxy=""
     port="80"
     mmsproxy=""
     mmsport=""
     mmsc=""
     type="default"
     read_only ="true"
     localized_name="APN_NAME_CUNET"/>
 <apn carrier="China Unicom"
     apn="M2M.NJM2MAPN"
     mcc="460"
     mnc="06"
     user=""
     server=""
     password=""
     proxy=""
      port=""
     mmsproxy=""
     mmsport=""
     mmsc=""
     type="default"/>
 <apn carrier="China Unicom"
     apn="unim2m.njm2mAPN"
     mcc="460"
     mnc="06"
     user=""
     server=""
     password=""
     proxy=""
     port=""
     mmsproxy=""
     mmsport=""
     mmsc=""
     type="default"/>
 <apn carrier="China Unicom 3G"
     apn="3gnet"
     mcc="460"
     mnc="06"
     user=""
     server=""
     password=""
     proxy=""
     port="80"
     mmsproxy=""
      mmsport=""
     mmsc=""
     type="supl"
     read_only ="true"
     localized_name="APN_NAME_CUSUPL"/>
 <apn carrier="China Unicom"
     apn="3gwap"
     mcc="460"
     mnc="06"
     user=""
     server=""
     password=""
     proxy=""
     port=""
     mmsproxy="10.0.0.172"
     mmsport="80"
     mmsc="http://mmsc.myuni.com.cn"
     type="mms"
     read_only ="true"
     localized_name="APN_NAME_CUMMS"/>
 <apn carrier="China Unicom wap"
     apn="3gwap"
     mcc="460"
     mnc="06"
     user=""
     server=""
     password=""
     proxy="10.0.0.172"
     port="80"
     mmsproxy=""
     mmsport=""
     mmsc=""
     type="default"
     read_only ="true"
     localized_name="APN_NAME_CUWAP"/>

apns-conf.xml APN接入点配置文件，在编译/system/etc目录下，但是在设备端/etc下也有apns-conf.xml，删除下图的/data/user_de/0/com.android.providers.telephony/databases下的文件telephony.dbHe telephony.db-journal并替换/system/etc和/etc下的旧的apns-conf.xml，重启即可。

为什么要删除db呢，因为RIL层在初始化拨号的时候会从sim卡中读取apn，然后把读出的apn和预先数据库中的apn对比，如果匹配就按照数据库的信息去拨号。

Android 7.0后SettingProviderContactsProvider TelephonyProvider MediaProvider数据库位置

http://blog.csdn.net/yin1031468524/article/details/71512996

Android 增加预置的APN信息

http://blog.csdn.net/zhoumushui/article/details/50786031