APN，这东西对于刚接触的人来说并不是那么好理解，对于3G移植上网必不可少，这里记录一下。
撰写不易,转载请注明出处：http://blog.csdn.net/jscese/article/details/41248939
概念：
APN(Access Point Name),也就是 接入点 ，移动设备使用数据流量上网必须配置的一个参数，代表以何种方式来连接服务台开启数据流量功能.
一般有访问WAP或者connect 因特网，国内的运营商2G，3G标识如下：
移动公司：2G:GSM、3G:TD-SCDMA
联通公司：2G:GSM、3G:WCDMA
电信公司：2G:CDMA、3G:CDMA2000
关于具体某个运营商的几G网络 的APN 是什么具体可参考/device/sample/etc/apns-full-conf.xml
这个xml文件中有google预置的多国常用的APN
使用：
apns-full-conf.xml
上面说道了apns-full-conf.xml 这个配置文件，这里面基本上是这样的模块：
<apn carrier="沃3G连接互联网 (China Unicom)"
mcc="460"
mnc="01"
apn="3gnet"
type="default,supl"
/>
其它选项都是网络参数，其中的apn就是我们最重要的接入点.也可自行添加apn属性模块.
移植3G时，就需要用到这个xml配置文件了，在android的device.mk 里面加个PRODUCT_COPY_FILES：
PRODUCT_COPY_FILES += \
device/sample/etc/apns-full-conf.xml:system/etc/apns-conf.xml
telephony.db
这个文件被加载的地方可参考/packages/providers/TelephonyProvider/src/com/android/providers/telephony/TelephonyProvider.java：
private static final String DATABASE_NAME = "telephony.db"; //数据库db文件
private static final String PARTNER_APNS_PATH = "etc/apns-conf.xml"; //上面说到的copy到系统system/etc目录下
...
private static class DatabaseHelper extends SQLiteOpenHelper {
// Context to access resources with
private Context mContext;
/**
* DatabaseHelper helper class for loading apns into a database.
*
* @param context of the user.
*/
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, getVersion(context));
mContext = context;
}
...
@Override
public void onCreate(SQLiteDatabase db) {
// Set up the database schema
db.execSQL("CREATE TABLE " + CARRIERS_TABLE + //建表
"(_id INTEGER PRIMARY KEY," +
"name TEXT," +
"numeric TEXT," +
"mcc TEXT," +
"mnc TEXT," +
"apn TEXT," +
"user TEXT," +
"server TEXT," +
"password TEXT," +
"proxy TEXT," +
"port TEXT," +
"mmsproxy TEXT," +
"mmsport TEXT," +
"mmsc TEXT," +
"authtype INTEGER," +
"type TEXT," +
"current INTEGER," +
"protocol TEXT," +
"roaming_protocol TEXT," +
"carrier_enabled BOOLEAN," +
"bearer INTEGER);");
initDatabase(db);
}
private void initDatabase(SQLiteDatabase db) {
...
// Environment.getRootDirectory() is a fancy way of saying ANDROID_ROOT or "/system".
File confFile = new File(Environment.getRootDirectory(), PARTNER_APNS_PATH); //这里就是加载解析 load进db 了
FileReader confreader = null;
try {
confreader = new FileReader(confFile);
confparser = Xml.newPullParser();
confparser.setInput(confreader);
XmlUtils.beginDocument(confparser, "apns");
// Sanity check. Force internal version and confidential versions to agree
int confversion = Integer.parseInt(confparser.getAttributeValue(null, "version"));
if (publicversion != confversion) {
throw new IllegalStateException("Internal APNS file version doesn't match "
+ confFile.getAbsolutePath());
}
loadApns(db, confparser);
}
...
}
}
因为Content Provider采用的是懒加载机制，所以只有检测load上sim卡的时候才会被创建这个db：
可使用sqlite3查看：
createAllApnList
在android中数据流量由/frameworks/opt/telephony/src/java/com/android/internal/telephony/DataConnectionTracker.java
以及它的子类GsmDataConnectionTracker.java(GSM模式) 或者 CdmaDataConnectionTracker.java(CDMA模式)，(前者为移动，联通，后者为电信专用)
来控制，其中启动数据流量开关为onSetUserDataEnabled(boolean enabled).
这里单以GSM模式来说，在SIM 被load时调用：
private void onRecordsLoaded() {
if (DBG) log("onRecordsLoaded: createAllApnList");
createAllApnList();
if(!mUserDataEnabled)
return;//jscese add judgement
if (mPhone.mCM.getRadioState().isOn()) {
if (DBG) log("onRecordsLoaded: notifying data availability");
notifyOffApnsOfAvailability(Phone.REASON_SIM_LOADED);
}
setupDataOnReadyApns(Phone.REASON_SIM_LOADED);
}
调用进createAllApnList
/**
* Based on the sim operator numeric, create a list for all possible
* Data Connections and setup the preferredApn.
*/
private void createAllApnList() {
mAllApns = new ArrayList<ApnSetting>();
IccRecords r = mIccRecords.get();
String operator = (r != null) ? r.getOperatorNumeric() : "";
if (operator != null) {
String selection = "numeric = '" + operator + "'";
// query only enabled apn.
// carrier_enabled : 1 means enabled apn, 0 disabled apn.
selection += " and carrier_enabled = 1";
if (DBG) log("createAllApnList: selection=" + selection);
Cursor cursor = mPhone.getContext().getContentResolver().query( //用当前SIM卡对应的运营商查询系统的所有APN，往下调用createApnList
Telephony.Carriers.CONTENT_URI, null, selection, null, null);
if (cursor != null) {
if (cursor.getCount() > 0) {
mAllApns = createApnList(cursor); //可以跟进去看查询Telephony.Carriers并返回一个Apn的list
}
cursor.close();
}
}
if (mAllApns.isEmpty()) {
if (DBG) log("createAllApnList: No APN found for carrier: " + operator);
mPreferredApn = null;
// TODO: What is the right behaviour?
//notifyNoData(GsmDataConnection.FailCause.MISSING_UNKNOWN_APN);
} else {
mPreferredApn = getPreferredApn();
if (mPreferredApn != null && !mPreferredApn.numeric.equals(operator)) {
mPreferredApn = null;
setPreferredApn(-1);
}
if (DBG) log("createAllApnList: mPreferredApn=" + mPreferredApn);
}
if (DBG) log("createAllApnList: X mAllApns=" + mAllApns);
}
onSetUserDataEnabled(true)：
代表打开数据流量，最终调用到
private boolean trySetupData(ApnContext apnContext)
{
...
if (apnContext.getState() == DctConstants.State.IDLE) {
ArrayList<ApnSetting> waitingApns = buildWaitingApns(apnContext.getApnType());
//使用用户设置的preferred APN构建一个可用于数据连接的备选APN列表，即waitingApns列表（当有preferred APN，该列表就只有一个）。
//若用户没有设置preferred APN，则将所有类型匹配的APN添加到waitingApns列表（如default类型）
if (waitingApns.isEmpty()) {
if (DBG) log("trySetupData: No APN found");
notifyNoData(GsmDataConnection.FailCause.MISSING_UNKNOWN_APN, apnContext);
notifyOffApnsOfAvailability(apnContext.getReason());
return false;
} else {
apnContext.setWaitingApns(waitingApns);
if (DBG) {
log ("trySetupData: Create from mAllApns : " + apnListToString(mAllApns));
}
}
}
if (DBG) {
log ("Setup watingApns : " + apnListToString(apnContext.getWaitingApns()));
}
// apnContext.setReason(apnContext.getReason());
boolean retValue = setupData(apnContext); // waitingApns列表中有可用的APN时，尝试建立连接
notifyOffApnsOfAvailability(apnContext.getReason());
return retValue;
...
}
另外几个对apn操作的几个函数都在这个文件里面，分别的作用如下：
onApnChanged：当APN被用户更改时，将调用到此函数，重新建立数据连接
setPreferredApn：当用户没有设置preferred APN时，将当前数据连接成功的那个APN设置为preferred APN。可以去看onDataSetupComplete时的操作。
getPreferredApn：用户获取用户设置的preferred APN，这个在上面说到的createAllApnList时会去获取一次，看是否存在.
对于这个preferredApn会以xml的形式保存在：
shell@android:/data/data/com.android.providers.telephony/shared_prefs # cat preferred-apn.xml ml < <?xml version='1.0' encoding='utf-8' standalone='yes' ?> <map> <long name="apn_id" value="1124" /> </map>
这是代表打开数据流量成功之后保存的apn map，可以像上面一样去 telephony.db里面查查看看：
sqlite> select * from carriers where _id='1124'; 1124|沃3G连接互联网 (China Unicom)|46001|460|01|3gnet|||||||||-1|default,supl|1|IP|IP|1|0
这里只是分析了一下apn的由来以及在framework层的使用，最终是通过RIL.java 的setupDataCall通过一个rild 的socket发请求到hardware的ril.cpp：
public void
setupDataCall(String radioTechnology, String profile, String apn, /*上面传下来的apn*/
String user, String password, String authType, String protocol,
Message result) {
RILRequest rr
= RILRequest.obtain(RIL_REQUEST_SETUP_DATA_CALL, result);
rr.mp.writeInt(7);
rr.mp.writeString(radioTechnology);
rr.mp.writeString(profile);
rr.mp.writeString(apn);
rr.mp.writeString(user);
rr.mp.writeString(password);
rr.mp.writeString(authType);
rr.mp.writeString(protocol);
if (RILJ_LOGD) riljLog(rr.serialString() + "> "
+ requestToString(rr.mRequest) + " " + radioTechnology + " "
+ profile + " " + apn + " " + user + " "
+ password + " " + authType + " " + protocol);
send(rr); //里面就是 socket了
}
再之后怎么获取到这个socket event处理并且交给reference-ril 发送这个apn接入网路可参考我前面的博客：