一．APN的简介

APN的完整说明在3GPP规范TS23.003 Clause 9中进行了详细定义。
MCCMNC的定义在3GPP规范TS23.003 Clause 2的IMSI定义中。

APN在GPRS骨干网中用来标识要使用的外部PDN（Packet data network，分组数据网，即常说的Internet），在GPRS网络中代表外部数据网络的总称。

APN由以下两部分组成：

APN网络标识：
是用户通过GGSN/PGW（Gateway GPRS Support Node，GPRS网关支持节点/PDN Gateway ，分组数据网网关）可连接到外部网络的标识，该标识由网络运营者分配给ISP（Internet Service Provider，因特网业务提供者）或公司，与其固定Internet域名一致，是APN的必选组成部分。例如 ， 定义移动用户通过该接入某公司的企业网，则APN的网络标识可以规划为“www.ABC123.com”。
APN运营者标识：
用于标识GGSN/PGW所归属的网络，是APN的可选组成部分。其形式为“MNCxxxx.MCCyyyy.gprs”（3G网络中），或者“MNCxxxx.MCCyyyy.3gppnetwork.org（4G网络中）。APN实际上就是对一个外部PDN的标识，这些PDN包括企业内部网、Internet、WAP网站、行业内部网等专用网络。

二．Apn参数的组成

例：移动apn，把所有的属性都放在一起如下

apn carrier=”中国移动彩信 (China Mobile)”
mcc=”460”
mnc=”00”
apn=”cmwap”
proxy=”10.0.0.172”
port=”80”
mmsc=”http://mmsc.monternet.com”
mmsproxy=”10.0.0.172”
mmsport=”80”
user=”mms”
password=”mms”
type=”mms”
authtype=”1”
protocol=”IPV4V6”
/>
其对应的属性定义如下：

Carrier：apn的名字，可为空，只用来显示apn列表中此apn的显示名字。
Mcc：由三位数组成。 用于识别移动用户的所在国家;
Mnc：由两位或三位组成。 用于识别移动用户的归属PLMN。 MNC的长度（两位或三位数）取决于MCC的值。
Apn：APN网络标识（接入点名称），是APN参数中的必选组成部分。此标识由运营商分配。
Proxy：代理服务器的地址
Port：代理服务器的端口号
Mmsc：MMS中继服务器/多媒体消息业务中心，是彩信的交换服务器。
Mmsproxy：彩信代理服务器的地址
Mmsport：彩信代理服务器的端口号
Protocol：支持的协议，不配置默认为IPV4。
User：用户
Password：密码
Authtype：apn的认证协议，PAP为口令认证协议，是二次握手机制。CHAP是质询握手认证协议，是三次握手机制。

None	0
PAP	1
CHAP	2
PAP or CHAP	3

Type: apn的接入点类型

Default	默认网络连接
Mms	彩信专用连接，此连接与default类似，用于与载体的多媒体信息服务器对话的应用程序
Supl	是Secure User Plane Location“安全用户面定位”的简写，此连接与default类似，用于帮助定位设备与载体的安全用户面定位服务器对话的应用程序
Dun	Dial Up Networking拨号网络的简称，此连接与default连接类似，用于执行一个拨号网络网桥，使载体能知道拨号网络流量的应用程序
Hipri	高优先级网络，与default类似，但路由设置不同。只有当进程访问移动DNS服务器，并明确要求使用requestRouteToHost(int, int)才会使用此连接

注意：此表中的数据连接优先级是由低到高，即default数据连接的优先级最低，而hipri数据连接的优先级最高。比如：手机上网聊天，建立的是default数据连接。如果此时接到一条彩信，由于彩信的数据连接是mms，优先级比default高，所以会先断开default数据连接，建立mms数据连接，让手机先收到彩信。所以收发彩信的同时不能上网。（单条pdp连接的情况）

注：mnc的位数由mcc决定。比如，墨西哥334020，此国家的mnc为020，mccmnc的值都固定在了SIM卡保存的IMSI中，配置apn参数时mnc不可简洁为20，否则apn列表中将读取不到此国家的334020运营商的参数。

三．Apn的存储以及初始化

apn在手机中的存储：

apn文件：System/etc/apn-conf.xml
apn数据存储的数据库：/data/data/com.android.providers.telephony/databases/ telephony.db
Carriers表

apn的初始化：

在启动手机时，需要初始化telephony.db数据库，这时候会读取手机目录System/etc/apn-conf.xml并把其中的内容加入到Carriers表中。以后查询有关apn的配置参数都是从Carriers表中取出。

创建并初始化Carriers表：
packages/providers/TelephonyProvider/src/com/android/providers/telephony/TelephonyProvider.java

内部类：DatabaseHelper.java

//创建数据库
由于添加了UNIQUE 约束条件，如果两个差不多的apn参数满足约束条件内的属性都相等，那么认为是同一组apn参数，将不会重复插入到数据库。

private void createCarriersTable(SQLiteDatabase db, String tableName) {// Set up the database schemaif (DBG) log("dbh.createCarriersTable start");String columns = "(_id INTEGER PRIMARY KEY," +NAME + " TEXT DEFAULT ''," +NUMERIC + " TEXT DEFAULT ''," +MCC + " TEXT DEFAULT ''," +MNC + " TEXT DEFAULT ''," +APN + " TEXT DEFAULT ''," +USER + " TEXT DEFAULT ''," +SERVER + " TEXT DEFAULT ''," +PASSWORD + " TEXT DEFAULT ''," +PROXY + " TEXT DEFAULT ''," +PORT + " TEXT DEFAULT ''," +MMSPROXY + " TEXT DEFAULT ''," +MMSPORT + " TEXT DEFAULT ''," +MMSC + " TEXT DEFAULT ''," +AUTH_TYPE + " INTEGER DEFAULT -1," +TYPE + " TEXT DEFAULT ''," +CURRENT + " INTEGER," +SOURCE_TYPE + " INTEGER DEFAULT 0," +CSD_NUM + " TEXT DEFAULT ''," +PROTOCOL + " TEXT DEFAULT IP," +ROAMING_PROTOCOL + " TEXT DEFAULT IP,";/// M: add for OMACP serviceif (OMACP_SUPPORT) {columns += OMACP_ID + " TEXT DEFAULT ''," +NAP_ID + " TEXT DEFAULT ''," +PROXY_ID + " TEXT DEFAULT '',";}columns += CARRIER_ENABLED + " BOOLEAN DEFAULT 1," +BEARER + " INTEGER DEFAULT 0," +BEARER_BITMASK + " INTEGER DEFAULT 0," +SPN + " TEXT DEFAULT ''," +IMSI + " TEXT DEFAULT ''," +PNN + " TEXT DEFAULT ''," +PPP + " TEXT DEFAULT ''," +MVNO_TYPE + " TEXT DEFAULT ''," +MVNO_MATCH_DATA + " TEXT DEFAULT '',";columns += SUBSCRIPTION_ID + " INTEGER DEFAULT " +SubscriptionManager.INVALID_SUBSCRIPTION_ID + "," +PROFILE_ID + " INTEGER DEFAULT 0," +MODEM_COGNITIVE + " BOOLEAN DEFAULT 0," +MAX_CONNS + " INTEGER DEFAULT 0," +WAIT_TIME + " INTEGER DEFAULT 0," +MAX_CONNS_TIME + " INTEGER DEFAULT 0," +MTU + " INTEGER DEFAULT 0," +EDITED + " INTEGER DEFAULT " + UNEDITED + "," +USER_VISIBLE + " BOOLEAN DEFAULT 1, " +USER_EDITABLE + " BOOLEAN DEFAULT 1," +// Uniqueness collisions are used to trigger merge code so if a field is listed// here it means we will accept both (user edited + new apn_conf definition)// Columns not included in UNIQUE constraint: name, current, edited,// user, server, password, authtype, type, protocol, roaming_protocol, sub_id,// modem_cognitive, max_conns, wait_time, max_conns_time, mtu, bearer_bitmask,// user_visible"UNIQUE (" + TextUtils.join(", ", CARRIERS_UNIQUE_FIELDS) + "));";db.execSQL("CREATE TABLE " + tableName + columns);db.execSQL("DROP TABLE IF EXISTS " + CARRIERS_DM_TABLE);db.execSQL("CREATE TABLE " + CARRIERS_DM_TABLE + columns);if (DBG) log("dbh.createCarriersTable:-");}

//读取apns-conf.xml文件，并初始化Carriers表。

private void initDatabase(SQLiteDatabase db) {if (VDBG) log("dbh.initDatabase:+ db=" + db);// Read internal APNS dataResources r = mContext.getResources();XmlResourceParser parser = r.getXml(com.android.internal.R.xml.apns);int publicversion = -1;try {XmlUtils.beginDocument(parser, "apns");publicversion = Integer.parseInt(parser.getAttributeValue(null, "version"));loadApns(db, parser);} catch (Exception e) {loge("Got exception while loading APN database." + e);} finally {parser.close();}// Read external APNS data (partner-provided)XmlPullParser confparser = null;File confFile = getApnConfFile();FileReader confreader = null;if (DBG) log("confFile = " + confFile);try {confreader = new FileReader(confFile);confparser = Xml.newPullParser();confparser.setInput(confreader);XmlUtils.beginDocument(confparser, "apns");// Sanity check. Force internal version and confidential versions to agreeint confversion = Integer.parseInt(confparser.getAttributeValue(null, "version"));if (publicversion != confversion) {log("initDatabase: throwing exception due to version mismatch");throw new IllegalStateException("Internal APNS file version doesn't match "+ confFile.getAbsolutePath());}db.beginTransaction();try {loadApns(db, confparser);db.setTransactionSuccessful();} finally {db.endTransaction();}} catch (FileNotFoundException e) {// It's ok if the file isn't found. It means there isn't a confidential file// Log.e(TAG, "File not found: '" + confFile.getAbsolutePath() + "'");} catch (Exception e) {loge("initDatabase: Exception while parsing '" + confFile.getAbsolutePath() + "'" +e);} finally {// Get rid of user/carrier deleted entries that are not present in apn xml file.// Those entries have edited value USER_DELETED/CARRIER_DELETED.if (VDBG) {log("initDatabase: deleting USER_DELETED and replacing "+ "DELETED_BUT_PRESENT_IN_XML with DELETED");}// Delete USER_DELETEDdb.delete(CARRIERS_TABLE, IS_USER_DELETED + " or " + IS_CARRIER_DELETED, null);// Change USER_DELETED_BUT_PRESENT_IN_XML to USER_DELETEDContentValues cv = new ContentValues();cv.put(EDITED, USER_DELETED);db.update(CARRIERS_TABLE, cv, IS_USER_DELETED_BUT_PRESENT_IN_XML, null);// Change CARRIER_DELETED_BUT_PRESENT_IN_XML to CARRIER_DELETEDcv = new ContentValues();cv.put(EDITED, CARRIER_DELETED);db.update(CARRIERS_TABLE, cv, IS_CARRIER_DELETED_BUT_PRESENT_IN_XML, null);if (confreader != null) {try {confreader.close();} catch (IOException e) {// do nothing}}// Update the stored checksumsetApnConfChecksum(getChecksum(confFile));}if (VDBG) log("dbh.initDatabase:- db=" + db);}

设置APN：
packages/apps/Settings/src/com/android/settings/ApnSettings.java
查询数据库Carriers表中的数据：

private void fillList() {final TelephonyManager tm = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);String mccmnc = mSubscriptionInfo == null ? "" : tm.getSimOperator(mSubscriptionInfo != null ? mSubscriptionInfo.getSubscriptionId(): SubscriptionManager.INVALID_SUBSCRIPTION_ID);/// M: for plug-in @{// use mcc&mnc in IMPI to query apn.Log.d(TAG, "before plugin, mccmnc = " + mccmnc);mccmnc = mApnExt.getOperatorNumericFromImpi(mccmnc,SubscriptionManager.getPhoneId(mSubscriptionInfo.getSubscriptionId()));/// @}Log.d(TAG, "mccmnc = " + mccmnc);/*StringBuilder where = new StringBuilder("numeric=\"" + mccmnc +"\" AND NOT (type='ia' AND (apn=\"\" OR apn IS NULL)) AND user_visible!=0");*/String where = "numeric=\"" + mccmnc + "\"";/// M: for [C2K APN Customization] @{if (mSubscriptionInfo != null) {int subId = mSubscriptionInfo.getSubscriptionId();if (CdmaUtils.isSupportCdma(subId)) {where = CdmaApnSetting.customizeQuerySelectionforCdma(where, mccmnc, subId);}}/// @}where += " AND NOT (type='ia' AND (apn=\"\" OR apn IS NULL)) AND user_visible!=0";/// M: for VoLTE, do not show ims apn for non-VoLTE project @{/*if (mHideImsApn) {where.append(" AND NOT (type='ims')");}*///if (!FeatureOption.MTK_VOLTE_SUPPORT || mHideImsApn) {where += " AND NOT (type='ims' OR type='ia,ims')";//}/// @}/// M: for plug-inwhere = mApnExt.getFillListQuery(where, mccmnc);Log.d(TAG, "fillList where: " + where);String order = mApnExt.getApnSortOrder(Telephony.Carriers.DEFAULT_SORT_ORDER);order = "_id asc";Log.d(TAG, "fillList sort: " + order);Cursor cursor = getContentResolver().query(Telephony.Carriers.CONTENT_URI,new String[] { "_id", "name", "apn", "type", "mvno_type", "mvno_match_data","sourcetype" }, where.toString(), null, order);if (cursor != null) {Log.d(TAG, "fillList, cursor count: " + cursor.getCount());IccRecords r = null;if (mUiccController != null && mSubscriptionInfo != null) {r = mUiccController.getIccRecords(SubscriptionManager.getPhoneId(mSubscriptionInfo.getSubscriptionId()), UiccController.APP_FAM_3GPP);}PreferenceGroup apnList = (PreferenceGroup) findPreference("apn_list");apnList.removeAll();/// M: for plug-in, use Preference instead ApnPreference for the// convenience of plug-in sideArrayList<Preference> mnoApnList = new ArrayList<Preference>();ArrayList<Preference> mvnoApnList = new ArrayList<Preference>();ArrayList<Preference> mnoMmsApnList = new ArrayList<Preference>();ArrayList<Preference> mvnoMmsApnList = new ArrayList<Preference>();mSelectedKey = getSelectedApnKey();cursor.moveToFirst();while (!cursor.isAfterLast()) {String name = cursor.getString(NAME_INDEX);String apn = cursor.getString(APN_INDEX);String key = cursor.getString(ID_INDEX);String type = cursor.getString(TYPES_INDEX);String mvnoType = cursor.getString(MVNO_TYPE_INDEX);String mvnoMatchData = cursor.getString(MVNO_MATCH_DATA_INDEX);/// M: check source type, some types are not editableint sourcetype = cursor.getInt(SOURCE_TYPE_INDEX);/// M: skip specific APN typeif(shouldSkipApn(type)) {cursor.moveToNext();continue;}/// M: for plug-inname = mApnExt.updateApnName(name, sourcetype);ApnPreference pref = new ApnPreference(getPrefContext());pref.setKey(key);pref.setTitle(name);pref.setSummary(apn);pref.setPersistent(false);pref.setOnPreferenceChangeListener(this);pref.setSubId(mSubscriptionInfo.getSubscriptionId());/// M: for [Read Only APN]pref.setApnEditable(mApnExt.isAllowEditPresetApn(type, apn, mccmnc, sourcetype));pref.setSubId(mSubscriptionInfo == null ? null : mSubscriptionInfo.getSubscriptionId());/// M: for ALPS02500557, do not select emergency APNboolean selectable = ((type == null) || (!type.equals("mms")&& !type.equals("ia") && !type.equals("ims") && !type.equals("emergency")))/// M: for plug-in&& mApnExt.isSelectable(type);pref.setSelectable(selectable);Log.d(TAG, "mSelectedKey = " + mSelectedKey + " key = " + key + " name = " + name +" selectable=" + selectable);if (selectable) {/// M: select prefer APN later, as the apn list are not solid now @{/*if ((mSelectedKey != null) && mSelectedKey.equals(key)) {pref.setChecked();}*//// @}addApnToList(pref, mnoApnList, mvnoApnList, r, mvnoType, mvnoMatchData);/// M: For CT feature,when apns-conf.xml add type extra value "supl",// selectable maybe ture when 46011 mms, so need this method.mApnExt.customizeUnselectableApn(type, mvnoType, mvnoMatchData, mnoApnList, mvnoApnList,mSubscriptionInfo == null ? null : mSubscriptionInfo.getSubscriptionId());} else {addApnToList(pref, mnoMmsApnList, mvnoMmsApnList, r, mvnoType, mvnoMatchData);/// M: for plug-inmApnExt.customizeUnselectableApn(type, mvnoType, mvnoMatchData, mnoMmsApnList, mvnoMmsApnList,mSubscriptionInfo == null ? null : mSubscriptionInfo.getSubscriptionId());}cursor.moveToNext();}cursor.close();if (!mvnoApnList.isEmpty()) {mnoApnList = mvnoApnList;mnoMmsApnList = mvnoMmsApnList;// Also save the mvno info}for (Preference preference : mnoApnList) {apnList.addPreference(preference);}for (Preference preference : mnoMmsApnList) {apnList.addPreference(preference);}/// M: always set a prefer APNsetPreferApnChecked(mnoApnList);/// M: update screen enable state according to airplane mode, SIM radio status, etc.updateScreenEnableState(getActivity());}}

packages/apps/Settings/src/com/android/settings/ApnEditor.java

各个国家mccmnc的查询：
http://www.gpsspg.com/bs/mnc.htm